| 1. |
- Adeyemi, Ahmed, et al.
(author)
-
Regio- and Stereoselective Synthesis of Allylic Spiroethers (Spirobenzofuranes) via an Intramolecular Mizoroki-Heck Reaction
- 2020
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:12, s. 7648-7657
-
Journal article (peer-reviewed)abstract
- The palladium(0)-catalyzed intramolecular annulation of 12 1,3-disubstituted cyclopentenes, derived from (+)-vincelactam, resulted in 5-exo cyclizations which furnished a series of 2,5-dimethyl-14(3R,4'S)-2H-spiro[benzofuran-3,1'-cyclopentan]2'-en-4'-yl)-1H-pyrroles in excellent diastereoselectivities and useful isolated yields. The double bond migration process that followed the arylpalladium insertion was controlled by a fine-tuning of the reaction system, which provided regioselectivities of up to 98:2. The selective Mizoroki-Heck reaction was used as the key transformation for preparing two new spirocyclic monoprotected amino acids as single stereoisomers.
|
|
| 2. |
- Adolfsson, Dan E., 1989-, et al.
(author)
-
Intramolecular Povarov Reactions for the Synthesis of Chromenopyridine fused 2-Pyridone Polyheterocycles Binding to α-Synuclein and Amyloid-β fibrils
- 2020
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:21, s. 14174-14189
-
Journal article (other academic/artistic)abstract
- A BF3×OEt2 catalyzed intramolecular Povarov reaction was used to synthesize a library of 15 chromenopyridine fused thiazolino-2-pyridone peptidomimetics. The reaction works with a range of O-alkylated salicylaldehydes and amino functionalized thiazolino-2-pyridones, to generate polyheterocycles with diverse substitution. The synthesized compounds were screened for their ability to bind α-synuclein and amyloid β fibrils in vitro. Analogs substituted with a nitro group bind to mature amyloid fibrils, and the activity moreover depends on the positioning of this functional group.
|
|
| 3. |
- Al-Smadi, Derar, 1983-, et al.
(author)
-
Chemical and Biochemical Approaches for the Synthesis of Substituted Dihydroxybutanones and Di-, and Tri-Hydroxypentanones
- 2019
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 84:11, s. 6982-6991
-
Journal article (peer-reviewed)abstract
- Polyhydroxylated compounds are building blocks for the synthesis of carbohydrates and other natural products. Their synthesis is mainly achieved by different synthetic versions of aldol-coupling reactions, catalyzed either by organocatalysts, enzymes or metal-organic catalysts. We have investigated the formation of 1,4-substituted 2,3-dihydroxybutan-1-one derivatives from para- and meta-substituted phenylacetaldehydes by three distinctly different strategies. The first involved a direct aldol reaction with hydroxyacetone, dihydroxyacetone or 2-hydroxyacetophenone, catalyzed by the cinchona derivative cinchonine. The second was reductive cross-coupling with methyl or phenyl glyoxal promoted by SmI2 resulting in either 5-substituted 3,4-dihydroxypentan-2-ones or 1,4 bis-phenyl substituted butanones, respectively. Finally, in the third case, aldolase catalysis was employed for synthesis of the corresponding 1,3,4-trihydroxylated pentan-2-one derivatives. The organocatalytic route with cinchonine generated distereomerically enriched syn products (de = 60−99 %), with moderate enantiomeric excesses (ee = 43−56%), but did not produce aldols with either hydroxyacetone or dihydroxyacetone as donor ketones. The SmI2-promoted reductive cross-coupling generated product mixtures with diastereomeric and enantiomeric ratios close to unity. This route allowed for the production of both 1-methyl- and 1-phenylsubstituted 2,3-dihydroxybutanones, at yields between 40−60%. Finally, the biocatalytic approach resulted in enantiopure syn (3R,4S) 1,3,4-trihydroxypentan-2-ones.
|
|
| 4. |
- Albers, Michael F, et al.
(author)
-
Amino acid building blocks for Fmoc solid-phase synthesis of peptides phosphocholinated at serine, threonine, and tyrosine
- 2013
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 78:6, s. 2715-2719
-
Journal article (peer-reviewed)abstract
- Phosphocholination of eukaryotic host cell proteins has recently been identified as a novel post-translational modification important for bacterial pathogenesis. Here, we describe the first straightforward synthetic strategy for peptides containing phosphocholinated serine, threonine, or tyrosine residues using preformed functional amino acid building blocks, fully compatible with standard Fmoc solid-phase peptide synthesis.
|
|
| 5. |
- Almqvist, Fredrik, et al.
(author)
-
Neighboring Group Participation in a Regio- and Stereoselective Chlorination of a Bicyclo[2.2.2]octanone
- 1996
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 61:20, s. 6947-6951
-
Journal article (peer-reviewed)abstract
- The zinc chloride-mediated acetylation of the optically active silyl enol ether 2a gave the beta-diketone 3a (48%) together with the regio- and stereoselectively chlorinated compound 4 (27%). The yield of 4 increased to 70% by starting from the O-acetyl derivative 2c. The chlorination most likely occurs via neighboring group participation by the endo acetoxy group.
|
|
| 6. |
- Almqvist, Fredrik, et al.
(author)
-
Synthesis of Optically Active endo, endo Bicyclo[2.2.2]octane-2,5- diol, Bicyclo[2.2.2]octan-2,5-dione and Related Compounds
- 1996
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 61:11, s. 3794-3798
-
Journal article (peer-reviewed)abstract
- Optically active C-2-symmetric (1S,2S,4S,5S)-bicyclo[2.2.2]octane-2,5-diol ((+)-12; 98% ee) and several selectivity protected optically active intermediates useful for synthetic transformations were synthesized via a 1,2-carbonyl transposition route starting from the easily available optically active (1R,4S,6S)-6-hydroxybicyclo[2.2.2]octan-2-one ((-)-2). The synthetic route also allowed the preparation of optically active (1S,4S)-bicyclo[2.2.2]octane-2,5-dione ((+)-14; 98% ee).
|
|
| 7. |
- Alonso, Diego, et al.
(author)
-
Deprotection of Sulfonyl Aziridines
- 1998
-
In: J. Org. Chem.. - : American Chemical Society (ACS). ; :63, s. 9455-9461
-
Journal article (peer-reviewed)
|
|
| 8. |
|
|
| 9. |
- An, N., et al.
(author)
-
Mechanistic insight into self-propagation in organo-mediated Beckmann rearrangement: A combined experimental and computational study.
- 2013
-
In: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 78:9, s. 4297-4302
-
Journal article (peer-reviewed)abstract
- Organo-mediated Beckmann rearrangement in the liquid phase, which has the advantage of high efficiency and straightforward experimental procedures, plays an important role in the synthesis of amides from oximes. However, the catalytic mechanisms of these organic-based promoters are still not well understood. In this work, we report a combined experimental and computational study on the mechanism of Beckmann rearrangement mediated by organic-based promoters, using TsCl as an example. A novel self-propagating cycle is proposed, and key intermediates of this self-propagating cycle are confirmed by both experiments and DFT calculations. In addition, the reason why cyclohexanone oxime is not a good substrate of the organo-mediated Beckmann rearrangement is discussed, and a strategy for improving the yield is proposed.
|
|
| 10. |
- Andersson, Hanna, 1979, et al.
(author)
-
Photochemically Induced Aryl Azide Rearrangement: Solution NMR Spectroscopic Identification of the Rearrangement Product
- 2017
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 82:3, s. 1812-1816
-
Journal article (peer-reviewed)abstract
- Photolysis of ethyl 3-azido-4,6-difluorobenzoate at room temperature in the presence of oxygen results in the regioselective formation of ethyl 5,7-difluoro-4-azaspiro[2.4]hepta-1,4,6-triene-1-carboxylate, presumably via the corresponding ketenimine intermediate which undergoes a photochemical four-electron electrocyclization followed by a rearrangement. The photorearrangement product was identified by multinuclear solution NMR spectroscopic techniques supported by DFT calculations.
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Angelin, Marcus, et al.
(author)
-
Crystallization-induced secondary selection from a tandem driven dynamic combinatorial resolution process
- 2008
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 73:9, s. 3593-3595
-
Journal article (peer-reviewed)abstract
- Crystallization-induced secondary selection from a tandem driven dynamic combinatorial library is presented. In a one-pot experiment, an initial nitroaldol equilibrium was kinetically driven by a tandem reaction resulting in a subsequent dynamic library of diastereoisomers. This library was then further driven by a phase change, resulting in amplification and isolation of a highly diastereomerically enriched and synthetically interesting isoindolinone.
|
|
| 14. |
- Angelin, Marcus, et al.
(author)
-
Diastereoselective One-Pot Tandem Synthesis of 3-Substituted Isoindolinones : A Mechanistic Investigation
- 2010
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 75:17, s. 5882-5887
-
Journal article (peer-reviewed)abstract
- The mechanism of a base-catalyzed one-pot reaction of 2-cyanobenzaldehyde and primary nitroalkanes, to produce 3-substituted isoindolinones, has been investigated. A route starting with a nitroaldol (Henry) reaction, followed by a subsequent cyclization and rearrangement, was supported by intermediate analogue synthesis and DFT calculations. Direct diastereoselective crystallization from the reaction mixture was also achieved and studied for a number of substrates. Furthermore, the 3-substituted isoindolinones are an interesting group of compounds, both present important natural products, as well as being precursors to other valuable building blocks.
|
|
| 15. |
- Angles d'Ortoli, Thibault, et al.
(author)
-
Structure-Reactivity Relationships of Conformationally Armed Disaccharide Donors and Their Use in the Synthesis of a Hexasaccharide Related to the Capsular Polysaccharide from Streptococcus pneumoniae Type 37
- 2017
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 82:15, s. 8123-8140
-
Journal article (peer-reviewed)abstract
- To advance the field of glycobiology, efficient synthesis methods of oligosaccharides and glycoconjugates are a requisite. In glycosylation reactions using superarmed donors, both selectivity and reactivity issues must be considered, and we herein investigate these aspects for differently protected beta-linked 2-O-glycosylated glucosyl donors carrying bulky tert-butyldimethylsilyl groups to different extents. The acceptors in reactions being secondary alcohols presents a challenging situation with respect to steric crowding. Conformational pyranose ring equilibria of the superarmed disaccharide donors with axial-rich substituents contained skew and boat conformations, and three-state models were generally assumed. With NIS/TfOH as the promotor, 2,6-di-tert-butyl-4-methylpyridine as the base, and a dichloromethane/toluene solvent mixture, ethyl 1-thio-beta-d-glucosyl disaccharide donors having 6-O-benzyl group(s) besides tert-butyldimethylsilyl groups were efficiently coupled at -40 degrees C to the hydroxyl group at position 3 of glucopyranosyl acceptors to form beta-(1 -> 2),beta-(1 -> 3)-linked trisaccharides, isolated in excellent 95% yield. The more axial-rich donors in skew and boat conformations are thus preorganized closer to the assumed transition state in these glycosylation reactions. The developed methodology was subsequently applied in the synthesis of a multibranched hexasaccharide related to the capsular polysaccharide from Streptococcus pneumoniae type 37, which consists of a beta-(1 -> 3)-linked backbone and a beta-(1 -> 2)-linked side chain of D-glucosyl residues in disaccharide repeating units.
|
|
| 16. |
- Arefalk, Anna, et al.
(author)
-
Stereoselective Synthesis of 3-Aminoindan-1-ones and Subsequent Incorporation into HIV-1 Protease Inhibitors
- 2006
-
In: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 71:3, s. 1265-1268
-
Journal article (peer-reviewed)abstract
- A new method for the stereoselective synthesis of 3-aminoindan-1-ones from triflates of salicylic sulfinyl imines and ethylene glycol vinyl ether has been developed. The reaction sequence starts with a regioselective Heck reaction followed by stereoselective Lewis acid mediated annulation. Acidic cleavage of the sulfinamides produced pure (R)- and (S)-3-aminoindan-1-ones, which were successfully isolated and incorporated into active HIV-1 protease inhibitors.
|
|
| 17. |
- Arvela, Riina K, et al.
(author)
-
A reassessment of the transition-metal free suzuki-type coupling methodology.
- 2005
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 70:1, s. 161-168
-
Journal article (peer-reviewed)abstract
- We present here a reassessment of our transition-metal free Suzuki-type coupling protocol. We believe that, although the reaction can be run without the need for addition of a metal catalyst, palladium contaminants down to a level of 50 ppb found in commercially available sodium carbonate are responsible for the generation of the biaryl rather than, as previously suggested, an alternative non-palladium-mediated pathway. We present a revised methodology for Suzuki couplings using ultralow palladium concentrations for use with aryl and vinyl boronic acids and discuss the effects of the purity of the boronic acid on the reaction.
|
|
| 18. |
- Arvela, Riina K., et al.
(author)
-
Highly regioselective internal heck arylation of hydroxyalkyl vinyl ethers by aryl halides in water
- 2007
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 72:17, s. 6390-6396
-
Journal article (peer-reviewed)abstract
- Highly regioselective and fast Pd(0)-catalyzed internal α-arylation of ethylene glycol vinyl ether with aryl halides was shown to be possible in water without the need for any halide scavengers or ionic liquid additives. This presents, to our knowledge, the first case of water being utilized in the selective arylation of electron-rich olefins. Resulting α-products were hydrolyzed and isolated as corresponding acetophenones in good to excellent yields when using aryl bromides and with good to moderate yields in the case of aryl iodides. Microwave irradiation was shown to be beneficial in activation of aryl chlorides toward the internal Heck arylation. The scope of the protocol was further increased to include different hydroxyalkyl vinyl ethers, these all giving selectively only branched α-products. Finally, the active role of the hydroxy group in directing the regioselectivity toward internal arylation of electron-rich olefins, even in nonpolar toluene, was revealed.
|
|
| 19. |
- Arvela, Riina K, et al.
(author)
-
Microwave-promoted Heck coupling using ultralow metal catalyst concentrations.
- 2005
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 70:5, s. 1786-1790
-
Journal article (peer-reviewed)abstract
- We show that Heck couplings can be performed in water using microwave heating and Pd catalyst concentrations as low as 500 ppb. The methodology is simple; all that is required as the catalyst is a stock solution of palladium.
|
|
| 20. |
|
|
| 21. |
- Aydin, Juhanes, et al.
(author)
-
Synthesis and catalytic application of chiral 1,1'-Bi-2-naphthol- and biphenanthrol-based pincer complexes: selective allylation of sulfonimines with allyl stannane and allyl trifluoroborate.
- 2007
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 72:13, s. 4689-4697
-
Journal article (peer-reviewed)abstract
- New easily accessible 1,1'-bi-2-naphthol- (BINOL-) and biphenanthrol-based chiral pincer complex catalysts were prepared for selective (up to 85% enantiomeric excess) allylation of sulfonimines. The chiral pincer complexes were prepared by a flexible modular approach allowing an efficient tuning of the selectivity of the catalysts. By employment of the different enantiomeric forms of the catalysts, both enantiomers of the homoallylic amines could be selectively obtained. Both allyl stannanes and allyl trifluoroborates can be employed as allyl sources in the reactions. The biphenanthrol-based complexes gave higher selectivity than the substituted BINOL-based analogues, probably because of the well-shaped chiral pocket generated by employment of the biphenanthrol complexes. The enantioselective allylation of sulfonimines presented in this study has important implications for the mechanism given for the pincer complex-catalyzed allylation reactions, confirming that this process takes place without involvement of palladium(0) species.
|
|
| 22. |
|
|
| 23. |
- Ayub, Rabia, et al.
(author)
-
Can Baird's and Clar's Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4nπ- and (4n + 2)π-Rings?
- 2017
-
In: Journal of Organic Chemistry. - : American Chemical Society. - 0022-3263 .- 1520-6904. ; 82:12, s. 6327-6340
-
Journal article (peer-reviewed)abstract
- Compounds that can be labeled as "aromatic chameleons" are π-conjugated compounds that are able to adjust their π-electron distributions so as to comply with the different rules of aromaticity in different electronic states. We used quantum chemical calculations to explore how the fusion of benzene rings onto aromatic chameleonic units represented by biphenylene, dibenzocyclooctatetraene, and dibenzo[a,e]pentalene modifies the first triplet excited states (T1) of the compounds. Decreases in T1 energies are observed when going from isomers with linear connectivity of the fused benzene rings to those with cis- or trans-bent connectivities. The T1 energies decreased down to those of the parent (isolated) 4nπ-electron units. Simultaneously, we observe an increased influence of triplet state aromaticity of the central 4n ring as given by Baird's rule and evidenced by geometric, magnetic, and electron density based aromaticity indices (HOMA, NICS-XY, ACID, and FLU). Because of an influence of triplet state aromaticity in the central 4nπ-electron units, the most stabilized compounds retain the triplet excitation in Baird π-quartets or octets, enabling the outer benzene rings to adapt closed-shell singlet Clar π-sextet character. Interestingly, the T1 energies go down as the total number of aromatic cycles within a molecule in the T1 state increases.
|
|
| 24. |
- Azzi, Emanuele, et al.
(author)
-
Visible Light Mediated Photocatalytic N‑Radical Cascade Reactivity of γ,δ-Unsaturated N‑Arylsulfonylhydrazones : A General Approach to Structurally Diverse Tetrahydropyridazines
- 2021
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 86:4, s. 3300-3323
-
Journal article (peer-reviewed)abstract
- Tetrahydropyridazines are of particular interest for their versatility as intermediates in organic synthesis and display pharmacological activity in several domains. Here, we describe the photocatalytic synthesis of different tetrahydropyridazines starting from gamma,delta-unsaturated N-arylsulfonylhydrazones. Simple structural changes of substrates result into three different pathways beginning from a common N-hydrazonyl radical, which evolves through a domino carboamination/dearomatization, a HAT process, or a photoinduced radical Smiles rearrangement to afford diverse tetrahydropyridazines. All reactions are carried out in very mild conditions, and the quite inexpensive [Ru(bpy)(3)]Cl-2 is used as the catalyst. Preliminary mechanism studies are presented, among them luminescence and electrochemical characterization of the involved species. Computational studies allow to rationalize the mechanism in accord with the experimental findings.
|
|
| 25. |
- Baeckstroem, P., et al.
(author)
-
Convenient Method for the Synthesis of Lineatin, a Pheromone Component of Trypodendron-Lineatum
- 1991
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 56:10, s. 3358-3362
-
Journal article (peer-reviewed)abstract
- Synthesis of racemic lineatin (1), a pheromone component of Trypodendron lineatum, is described. Condensation of 5-methyl-5-hexen-2-one (2) and triethyl phosphonoacetate with LiN(SiMe3)2 gave esters 3, which upon hydrolysis gave acids 4a-f. The bicyclo[3.2.0] ring compounds 5 and 6 were obtained via an intramolecular [2 + 2] addition by refluxing underivatized carboxylic acids 4a-f with NaOAc and Ac2O. Compound 5 was isomerized to the thermodynamically more stable isomer 6 using a Pd/C catalyst activated with hydrogen. Reduction of 6 with LiAlH4 gave the endo and exo isomers 7a and 7b (4:1). Isolation of the alcohol 7a followed by acetylation gave 8. Subsequent oxidation with OsO4 and methylmorpholine N-oxide gave diol 9. Cleavage of 9 with H5IO6 in diethyl ether gave keto aldehyde 10, which was converted to keto acetal 11. Treatment of 11 with MeMgBr followed by acidic workup gave 1. The overall efficiency is approximately 20%.
|
|
| 26. |
|
|
| 27. |
- Baumruck, A. C., et al.
(author)
-
Native Chemical Ligation of Highly Hydrophobic Peptides in Ionic Liquid-Containing Media
- 2021
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 86:2, s. 1659-1666
-
Journal article (peer-reviewed)abstract
- The chemical synthesis of a highly hydrophobic membrane-associated peptide by native chemical ligation (NCL) in an ionic liquid (IL) [C2mim][OAc]/buffer mixture was achieved by employing peptide concentrations up to 11 mM. NCL was studied at different pH and water content and compared to several "gold-standard"ligation protocols. The optimized reaction protocol for the NCL in IL required the addition of 40% water and pH adjustment to 7.0-7.5, resulting in ligation yields of up to 80-95% within 1 to 4 h. This new ligation protocol is generally applicable and outperforms current "gold-standard"NCL methods. ©
|
|
| 28. |
- Belda, O., et al.
(author)
-
Highly stereo- and regioselective allylations catalyzed by Mo-pyridylamide complexes : Electronic and steric effects of the ligand
- 2000
-
In: Journal of Organic Chemistry. - Uppsala Univ, Uppsala Biomed Ctr, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. Royal Inst Technol, Dept Chem, SE-10044 Stockholm, Sweden. : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 65:18, s. 5868-5870
-
Journal article (peer-reviewed)
|
|
| 29. |
- Bengtson, A, et al.
(author)
-
Protected indanones by a Heck-Aldol annulation reaction
- 2002
-
In: Journal of Organic Chemistry. - Uppsala Univ, Dept Organ Pharmaceut Chem, SE-75123 Uppsala, Sweden. : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 67:16, s. 5854-5856
-
Journal article (peer-reviewed)abstract
- Monoprotected 3-hydroxyindan-1-ones have been prepared in moderate to good yields by a new tandem reaction involving salicylaldehyde triflates and commercially available 2-hydroxyethyl vinyl ether. This one-pot annulation reaction proceeds in the presence of a palladium bidentate catalyst and results in the formation of two new ring systems.
|
|
| 30. |
|
|
| 31. |
- Bengtsson, Christoffer, et al.
(author)
-
Regioselective Halogenations and Subsequent Suzuki-Miyaura Coupling onto Bicyclic 2-Pyridones
- 2010
-
In: The Journal of organic chemistry. - : American Chemical Society. - 1520-6904 .- 0022-3263. ; 75:3, s. 972-5
-
Journal article (peer-reviewed)abstract
- A selective synthesis of 6-bromo-8-iodo dihydro thiazolo ring-fused 2-pyridones is described. These halogenated 2-pyridones are selectively arylated by sequential Suzuki-Miyaura couplings. This approach can advantageously be used to synthesize focused libraries of substituted ring-fused 2-pyridones, a class of compounds with novel antibacterial properties.
|
|
| 32. |
- Bergman, Jan, et al.
(author)
-
Oxidative Ring Expansion of Spirocyclic Oxindole Derivatives
- 2014
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:19, s. 9065-9073
-
Journal article (peer-reviewed)abstract
- Oxidation of the spirocyclic oxindole derivative, isamic acid 1, led to decarboxylation and ring expansion to quinazolino[4,5-b]quinazoline-6,8-dione 7 rather than, as previously believed, its isomer 6. The structure of 7 was confirmed by X-ray crystallography. Condensation of isatin (indole-2,3-dione) and 2-aminobenzamide led to the spirocyclic molecule, spiro[3H-indole-3,2'(1H)quinazoline]-2,4'(1H,3H)dione 8, which was also identified as an intermediate in the oxidation of isamic acid. Mild hydrolysis of 7 gave the 10-membered molecule 22. Isamic acid could easily be converted to N-nitrosoisamic acid, which when heated in ethanol underwent a ring expansion to a hydroximino derivative, 38, of compound 6. The structure of 38 was confirmed by X-ray crystallography.
|
|
| 33. |
- Bergman, J., et al.
(author)
-
Thionations using a P4S10-pyridine complex in solvents such as acetonitrile and dimethyl sulfone
- 2011
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:6, s. 1546-1553
-
Journal article (peer-reviewed)abstract
- Tetraphosphorus decasulfide (P 4S 10) in pyridine has been used as a thionating agent for a long period of time. The moisture-sensitive reagent has now been isolated in crystalline form, and the detailed structure has been determined by X-ray crystallography. The thionating power of this storable reagent has been studied and transferred to solvents such as acetonitrile in which it has proven to be synthetically useful and exceptionally selective. Its properties have been compared with the so-called Lawesson reagent (LR). Particularly interesting are the results from thionations at relatively high temperatures (̃165 °C) in dimethyl sulfone as solvent. Under these conditions, for instance, acridone and 3-acetylindole could quickly be transformed to the corresponding thionated derivatives. Glycylglycine similarly gave piperazinedithione. At these temperatures, LR is inefficient due to rapid decomposition. The thionated products are generally cleaner and more easy to obtain because in the crystalline reagent, impurities which invariably are present in the conventional reagents, P 4S 10 in pyridine or LR, have been removed.
|
|
| 34. |
- Bielawski, Marcin, et al.
(author)
-
Regiospecific One-Pot Synthesis of Diaryliodonium Tetrafluoroborates from Arylboronic Acids and Aryl Iodides
- 2008
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 73:12, s. 4602-4607
-
Journal article (peer-reviewed)abstract
- Diaryliodonium salts have recently received considerable attention as mild arylation reagents in organic synthesis. This paper describes a regiospecific, sequential one-pot synthesis of symmetrical and unsymmetrical diaryliodonium tetrafluoroborates, which are the most popular salts in metal-catalyzed arylations. The protocol is fast and high-yielding and has a large substrate scope. Furthermore, the corresponding diaryliodonium triflates can conveniently be obtained via an in situ anion exchange.
|
|
| 35. |
- Billing, Johan, et al.
(author)
-
C2-Symmetric Macrocyclic Carbohydrate/Amino Acid Hybrids through Copper(I)-Catalyzed Formation of 1,2,3-Triazoles
- 2005
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 70:12, s. 4847-4850
-
Journal article (peer-reviewed)abstract
- An efficient method was developed for the preparation of macrocyclic carbohydrate/amino acid hybrids by macrocyclization with copper(I)-catalyzed 1,2,3-triazole formation. Methyl 2-amino-6-azido-3,4-di-O-benzoyl-2,6-dideoxy--D-glucopyranoside was prepared and coupled to two different N-propiolyl dipeptides (propiolyl-Tyr-Tyr-OH and propiolyl-Arg(Mtr)-Tyr-OH) to obtain bifunctional molecules carrying one azido group and one terminal alkyne. These bifunctional molecules were cyclodimerized using Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes to form macrocycles containing two 1,2,3-triazoles. Various cyclization methods were evaluated, and the most efficient conditions were found to be CuI and N,N-diisopropylethylamine in CH3CN.
|
|
| 36. |
- Biosca, Maria, et al.
(author)
-
Mechanism of Asymmetric Homologation of Alkenylboronic Acids with CF3-Diazomethane via Borotropic Rearrangement
- 2024
-
In: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 89:7, s. 4538-4548
-
Journal article (peer-reviewed)abstract
- Density functional theory calculations have been performed to investigate the mechanism for the BINOL-catalyzed asymmetric homologation of alkenylboronic acids with CF3-diazomethane. The reaction proceeds via a chiral BINOL ester of the alkenylboronic acid substrate. The calculations reveal a complex scenario for the formation of the chiral BINOL-alkenylboronate species, which is the key intermediate in the catalytic process. The aliphatic alcohol additive plays an important role in the reaction. This study provides a rationalization of the stereoinduction step of the reaction, and the enantioselectivity is mainly attributed to the steric repulsion between the CF3 group of the diazomethane reagent and the γ-substituent of the BINOL catalyst. The complex potential energy surface obtained by the calculations is analyzed by means of microkinetic simulations.
|
|
| 37. |
|
|
| 38. |
- Blid, Jan, et al.
(author)
-
Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic alpha-Amino Amides
- 2004
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:9, s. 3043-3049
-
Journal article (peer-reviewed)abstract
- Boron trifluoride and BBr3 mediated [2,3]-sigmatropic rearrangements of allylic alpha-amino amides have been developed affording secondary amines in good yields. (E)-Crotyl and (E)-cinnamyl alpha-amino amides 2b and 2c exhibit excellent syn-diastereoselectivity upon rearrangement with either Lewis acid. The allylic amine 2a forms upon treatment with BF3 or BBr3 a five-membered heterocylic complex in which a single halide anion has been displaced by the carbonyl oxygen atom. The structures of the Lewis acid-amine complexes were elucidated using NMR spectroscopy. A plausible reaction mechanism, based on DFT calculations, is presented. Thus, BF3- or BBr3-complexed allylic amines 2 are shown to preferentially proceed, after deprotonation, via an endo transition state.
|
|
| 39. |
- Blid, Jan, et al.
(author)
-
Lewis acid mediated asymmetric 2,3 -sigmatropic rearrangement of allylic amines. Scope and mechanistic investigation
- 2007
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 72:4, s. 1294-1300
-
Journal article (peer-reviewed)abstract
- [GRAPHIC] The first asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines has been realized by quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process, and support for this model was obtained from an NMR spectroscopic investigation of the chiral Lewis acid-substrate complex. The structure of the Lewis acid-product complex was established by X-ray crystallographic analysis and supported the proposed mechanism.
|
|
| 40. |
- Blomberg, David, et al.
(author)
-
Synthesis and conformational studies of a β-turn mimetic incorporated in Leu-enkephalin
- 2004
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:10, s. 3500-3508
-
Journal article (peer-reviewed)abstract
- A β-turn mimetic in which the four amino acids of a β-turn have been replaced by a 10-membered ring has been designed, synthesized, and subjected to conformational studies. In the mimetic, the intramolecular COi − HNi+3 hydrogen bond that is often found in β-turns has been replaced by an ethylene bridge. In addition, the amide bond between residues i and i + 1 was exchanged for a methylene ether isoster. Such a β-turn mimetic, based on the first four residues of Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu), was prepared in 15 steps. The synthesis relied on a β-azido alcohol prepared in five steps from Cbz-Tyr(tBu)-OH as a key, i-position building block. tert-Butyl bromoacetate, glycine, and a Phe-Leu dipetide were then used as building blocks for positions i + 1, i + 2, and i + 3, respectively. Conformational studies based on 1H NMR data showed that the β-turn mimetic was flexible, but that it resembled a type-II β-turn at low temperature. This low energy conformer closely resembled the structure determined for crystalline Leu-enkephalin.
|
|
| 41. |
- Borg, Tessie, et al.
(author)
-
Lewis Acid-Promoted Addition of 1,3-Bis(silyl)propenes to Aldehydes : A Route to 1,3-Dienes
- 2011
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:19, s. 8070-8075
-
Journal article (peer-reviewed)abstract
- The Lewis acid-promoted addition of 1,3-bis(silyl)-propenes to aldehydes to provide the corresponding (E)-1,3-dienes in excellent stereoselectivity and good to excellent yields is reported. The procedure is mild, base-free, and operationally straightforward.
|
|
| 42. |
- Bornhof, Anna-Bea, et al.
(author)
-
Rational Synthesis of 2-Bromoporphyrins and 2,12-Dibromoporphyrins
- 2017
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 82:23, s. 12908-12913
-
Journal article (peer-reviewed)abstract
- Bromoporphyrins were prepared by the metal-mediated self-condensation of brominated 1-formyldipyrromethanes. Depending on the conditions, Mg(II)-2,12-dibromoporphyrin and Mg(II)-2-bromoporphyrin could be obtained in up to 11% and 17% isolated yield, respectively. Zn(II) was also a viable templating metal. The positions of the bromine substituents were confirmed by 2D-NMR spectroscopic analysis and the X-ray crystal structure of a derivative. Suzuki and Sonogashira reactions of the bromoporphyrins yielded 2-substituted or 2,12-disubstituted porphyrins with red-shifted absorption and emission spectra. This method provides access to the minimalist core of beta-mono- and beta,beta'-disubstituted porphyrins from readily available starting materials.
|
|
| 43. |
- Bouchet, Aude, et al.
(author)
-
Conformational Effects Induced by Guest Encapsulation in an Enantiopure Water-Soluble Cryptophane
- 2011
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:5, s. 1372-1383
-
Journal article (peer-reviewed)abstract
- A new water-soluble cryptophane 1 derivative (penta-hydroxyl cryptophane-A) has been synthesized from cryptophanol-A and the chiroptical properties of its two enantiomers M M-1 and P P-1 have been studied by polarimetry, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD). Cryptophane 1 shows specific circular dichroism responses upon complexation that depend on the size of the guest and on the nature of the counterion (Li+, Na+, K+, Cs+) present in the solution. In LiOH and NaOH solutions, chiroptical changes induced by the encapsulation of guests and by the presence of cations in the vicinity of hosts can be interpreted from molecular dynamics (MD) and ab initio calculations by subtle conformational changes of the bridges. In KOH solution, the exchange dynamics is dependent on the size of the guest molecules, whereas in CsOH solution no encapsulation effect is observed whatever the size of the guest molecule. This last behavior comes from the fact that host 1 exhibits a very high affinity for cesium cations.
|
|
| 44. |
- Bouchet, Aude, et al.
(author)
-
Enantioselective Complexation of Chiral Propylene Oxide by an Enantiopure Water-Soluble Cryptophane
- 2011
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:10, s. 4178-4181
-
Journal article (peer-reviewed)abstract
- ECD and NMR experiments show that the complexation of propylene oxide (PrO) within the cavity of an enantiopure water-soluble cryptophane 1 in NaOH solution is enantioselective and that the (R)-PrO@PP-1 diastereomer is more stable than the (S)-PrO@PP-1 diastereomer with a free energy difference of 1.7 kJ/mol. This result has been confirmed to by molecular dynamics (MD) and ab initio calculations. The enantioselectivity is preserved in LiOH and KOH solutions even though the binding constants decrease, whereas PrO is not complexed in CsOH solution.
|
|
| 45. |
- Bouchet, Aude, et al.
(author)
-
Influence of the Chemical Structure of Water-Soluble Cryptophanes on Their Overall Chiroptical and Binding Properties
- 2011
-
In: Journal of Organic Chemistry. - : American Chemical Society. - 0022-3263 .- 1520-6904. ; 76:19, s. 7816-7825
-
Journal article (peer-reviewed)abstract
- The synthesis and the chiroptical properties of the two enantiomers of the hexacarboxylic acid cryptophane-A derivative, 1, are described in this article. The chiroptical and binding properties of 1 toward achiral and chiral guests have been investigated in water under basic conditions by polarimetry, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and (1)H NMR spectroscopy. These experiments reveal that the (1)H NMR spectra of 1 are very sensitive to the nature of the guest trapped in its cavity whereas ECD and VCD spectra remain unchanged. We also show that the two enantiomers of 1 are able to distinguish between the two enantiomers of a series of small chiral epoxides. The enantiodiscrimination increases with the size of the chiral guest whereas the corresponding binding constants decrease. In contrast to what was observed for other water-soluble cryptophanes, the molecular recognition process is found independent of the nature of the counterions surrounding host 1, shedding light on the importance of the chemical structure of cryptophanes on their binding and chiroptical properties.
|
|
| 46. |
|
|
| 47. |
- Bratt, Emma, et al.
(author)
-
A General Suzuki Cross-Coupling Reaction of Heteroaromatics Catalyzed by Nanopalladium on Amino-Functionalized Siliceous Mesocellular Foam
- 2014
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:9, s. 3946-3954
-
Journal article (peer-reviewed)abstract
- Suzuki-Miyaura cross-coupling reactions of heteroaromatics catalyzed by palladium supported in the cavities of amino-functionalized siliceous mesocellular foam are presented. The nanopalladium catalyst effectively couples not only heteroaryl halides with boronic acids but also heteroaryl halides with boronate esters, potassium trifluoroborates, MIDA boronates, and triolborates, producing a wide range of heterobiaryls in good to excellent yields. Furthermore, the heterogeneous palladium nanocatalyst can easily be removed from the reaction mixture by filtration and recycled several times with minimal loss in activity. This catalyst provides an alternative, environmentally friendly, low-leaching process for the preparation of heterobiaryls.
|
|
| 48. |
- Brea, Oriana, et al.
(author)
-
Mechanisms of Formation and Rearrangement of Benziodoxole-Based CF3 and SCF3 Transfer Reagents
- 2020
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:23, s. 15577-15585
-
Journal article (peer-reviewed)abstract
- Togni's benziodoxole-based reagents are widely used in trifluoromethylation reactions. It has been established that the kinetically stable hypervalent iodine form (I-CF3) of the reagents is thermodynamically less stable than its acyclic ether isomer (O-CF3). On the other hand, the trifluoromethylthio analogue exists in the thermodynamically stable thioperoxide form (O-SCF3), and the hypervalent form (I-SCF3) has been elusive. Despite the importance of these reagents, very little is known about the reaction mechanisms of their syntheses, which has hampered the development of new reagents of the same family. Herein, we use density functional theory calculations to understand the reasons for the divergent behaviors between the CF3 and SCF3 reagents. We demonstrate that they follow different mechanisms of formation and that the metals involved in the syntheses (potassium in the case of the trifluoromethyl reagent and silver in the trifluoromethylthio analogue) play key roles in the mechanisms and greatly influence the possibility of their rearrangements from the hypervalent (I-CF3, I-SCF3) to the corresponding ether-type form (O-CF3, O-SCF3).
|
|
| 49. |
- Brea, Oriana, et al.
(author)
-
Modeling Decomposition of N-Nitrosoamides in a Self-Assembled Capsule
- 2019
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 84:11, s. 7354-7361
-
Journal article (peer-reviewed)abstract
- Density functional theory calculations are employed to investigate the mechanism and energies of the decomposition of N-nitrosoamides in the presence of a resorcinarene-based self-assembled nanocapsule. From experiments, it is known that confinement in the capsule inhibits the thermal decomposition of these compounds. N-Nitrosoamides with both aromatic and aliphatic substituents are considered here and the calculations show that, for both kinds, binding to the capsule leads to a significant increase in the energy barrier of the rate-determining step, the 1,3 N -> O acyl transfer reaction. A distortion-interaction analysis is conducted to probe the reasons behind the inhibition of the reaction. In addition, we characterized hypothetical intermediates that might be involved in the formation of the decomposition products inside the capsule. Interestingly, it is found that the capsule stabilizes ion-pair species that are unstable in mesitylene solution. Finally, a possible explanation is proposed for the observed encapsulation of the decomposition product of only one of the substrates.
|
|
| 50. |
- Bremberg, U, et al.
(author)
-
Rapid microwave-induced palladium-catalyzed asymmetric allylic alkylation
- 1999
-
In: Journal of Organic Chemistry. - Royal Inst Technol, Dept Chem Organ Chem, S-10044 Stockholm, Sweden. Uppsala Univ, Uppsala Biomed Ctr, Dept Organ Pharmaceut Chem, S-75123 Uppsala, Sweden. : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 64, s. 1082-
-
Journal article (peer-reviewed)
|
|
