| 1. |
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| 2. |
- Agrawal, Santosh, et al.
(författare)
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Readily Available Ruthenium Complex for Efficient Dynamic Kinetic Resolution of Aromatic alpha-Hydroxy Ketones
- 2014
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 16:8, s. 2256-2259
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Tidskriftsartikel (refereegranskat)abstract
- A ruthenium complex formed from commercially available [Ru(p-cymene)Cl-2](2) and 1,4-bis(diphenylphosphino)butane catalyzes the racemization of aromatic alpha-hydroxy ketones very efficiently at room temperature. The racemization is fully compatible with a kinetic resolution catalyzed by a lipase from Pseudomonas stutzeri. This is the first example of dynamic kinetic resolution of alpha-hydroxy ketones at ambient temperature in which the metal and enzyme catalysts work in concert in one pot at room temperature to give quantitative yields of esters of alpha-hydroxy ketones with very high enantioselectivity.
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| 3. |
- Agrawal, Santosh, et al.
(författare)
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Selective Alkylation of (Hetero)Aromatic Amines with Alcohols Catalyzed by a Ruthenium Pincer Complex
- 2012
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 14:6, s. 1456-1459
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Tidskriftsartikel (refereegranskat)abstract
- A readily available pincer ruthenium(II) complex catalyzes the selective monoalkylation of (hetero)aromatic amines with a wide range of primary alcohols (including pyridine-, furan-, and thiophene-substituted alcohols) with high efficiency when used in low catalyst loadings (1 mol %). Tertiary amine formation via polyalkylation does not occur, making this ruthenium system an excellent catalyst for the synthesis of sec-amines.
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| 4. |
- Akkarasamiyo, Sunisa, et al.
(författare)
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Nickel-Catalyzed Suzuki-Miyaura Cross-Coupling Reaction of Naphthyl and Quinolyl Alcohols with Boronic Acids
- 2019
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 21:12, s. 4782-4787
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Tidskriftsartikel (refereegranskat)abstract
- A nickel-catalyzed C(sp(3))-C(sp(2)) Suzuki cross-coupling of arylboronic acids and (hetero)naphthyl alcohols has been developed. A Ni(dppp) Cl-2 complex showed the highest efficiency and broadest substrate scope. High functional group tolerance has been achieved where 35 compounds could be generated in good to excellent yields, including both primary and secondary benzylic alcohols. Mechanistic studies using multiple NMR techniques as well as ESI-HRMS showed that the C-O cleavage is facilitated by an activation of the benzylic alcohol through formation of a boronic ester intermediate.
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| 5. |
- Alam, Rauful, et al.
(författare)
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Selective Formation of Adjacent Stereocenters by Allylboration of Ketones under Mild Neutral Conditions
- 2013
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 15:10, s. 2546-2549
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Tidskriftsartikel (refereegranskat)abstract
- Allylboronic acids readily react with a broad variety of ketones, affording homoallylic alcohols with adjacent quaternary and tertiary stereocenters. The reaction proceeds with very high anti stereoselectivity even if the substituents of the keto group have a similar size. a-Keto acids react with syn stereoselectivity probably due to the formation of acyl boronate intermediates. The allylation reactions proceed without added acids/bases under mild conditions. Because of this, many functionalities are tolerated even with in situ generated allylboronic acids.
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| 6. |
- Alamsetti, Santosh Kumar, et al.
(författare)
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Palladium-Catalyzed Intramolecular Hydroamination of Propargylic Carbamates and Carbamothioates
- 2014
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 16:5, s. 1434-1437
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Tidskriftsartikel (refereegranskat)abstract
- An efficient and simple methodology was developed for the synthesis of oxazolidinones, oxazolidinthiones, imidazolidinthiones, and imidazolidinones from the corresponding propargylic starting materials using Pd(OAc)(2) and n-Bu4NOAc as catalysts in DCE at room temperature.
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| 7. |
- Albers, Michael F, et al.
(författare)
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Amino acid building blocks for efficient Fmoc solid-phase synthesis of peptides adenylylated at serine or threonine
- 2011
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 13:22, s. 6014-6017
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Tidskriftsartikel (refereegranskat)abstract
- The first straightforward building block based (non-interassembly) synthesis of peptides containing adenylylated serine and threonine residues is described. Key features include final global acidolytic protective group removal as well as full compatibility with standard Fmoc solid-phase peptide synthesis (SPPS). The described Thr-AMP SPPS-building block has been employed in the synthesis of the Thr-adenylylated sequence of human GTPase CDC42 (Ac-SEYVP-T(AMP)-VFDNYGC-NH(2)). Further, we demonstrate proof-of-concept for the synthesis of an Ser-adenylylated peptide (Ac-GSGA-S(AMP)-AGSGC-NH(2)) from the corresponding adenylylated serine building block.
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| 8. |
- Amorati, Riccardo, et al.
(författare)
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Organochalcogen Substituents in Phenolic Antioxidants
- 2010
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 12:10, s. 2326-2329
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the ED/EW character of organochalcogen substituents and their contribution to the O-H bond dissociation enthalpy (BDE) in phenolic compounds. A series of ortho- and para-(S,Se,Te)R-substituted phenols were prepared and investigated by EPR, IR, and computational methods. Substituents lowered the O-H BDE by >3 kcal/mol in the para position, while the ortho-effect was modest due to hydrogen bonding ( approximately 3 kcal/mol) to the O-H group.
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| 9. |
- Andersson, Hans, et al.
(författare)
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Complete regioselective addition of grignard reagents to pyrazine N-oxides, toward an efficient enantioselective synthesis of substituted piperazines.
- 2010
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Ingår i: Organic letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 12:2, s. 284-6
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Tidskriftsartikel (refereegranskat)abstract
- A conceptually new one-pot strategy for the synthesis of protected substituted piperazines via the addition of Grignard reagents to pyrazine N-oxides is presented. This strategy is high yielding (33-91% over three steps), step-efficient, and fast. The synthesized N,N-diprotected piperazines are convenient to handle and allow for orthogonal deprotection at either nitrogen for selective transformations. In addition, this is a synthetic route to enantiomerically enriched piperazines by using a combination of phenyl magnesium chloride and (-)-sparteine, which resulted in enantiomeric excesses up to 83%.
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| 10. |
- Andersson, Hans, et al.
(författare)
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Synthesis of 2-Substituted Pyridines via a Regiospecific Alkylation, Alkynylation, and Arylation of Pyridine N-Oxides
- 2007
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 9:7, s. 1335-7
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Tidskriftsartikel (refereegranskat)abstract
- Sequential addition of Grignard reagents to pyridine N-oxides in THF at room temperature followed by treatment with acetic anhydride at 120 C afforded 2-substituted pyridines in good to high yields. Furthermore, by exchanging acetic anhydride for DMF in the second step, 2-substituted pyridine N-oxides were obtained, as intermediates suitable for addition of a second Grignard reagent for the synthesis of 2,6-disubstituted pyridines.
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