| 1. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Castoldi, Laura, et al.
(författare)
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Electrophilic Vinylation of Thiols under Mild and Transition Metal-Free Conditions
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:36, s. 15512-15516
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Tidskriftsartikel (refereegranskat)abstract
- The iodine(III) reagents vinylbenziodoxolones (VBX) were employed to vinylate a series of aliphatic and aromatic thiols, providing E-alkenyl sulfides with complete chemo- and regioselectivity, as well as excellent stereoselectivity. The methodology displays high functional group tolerance and proceeds under mild and transition metal-free conditions without the need for excess substrate or reagents. Mercaptothiazoles could be vinylated under modified conditions, resulting in opposite stereoselectivity compared to previous reactions with vinyliodonium salts. Novel VBX reagents with substituted benziodoxolone cores were prepared, and improved reactivity was discovered with a dimethyl-substituted core.
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| 3. |
- Di Tommaso, Ester Maria, et al.
(författare)
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Explaining Regiodivergent Vinylations with Vinylbenziodoxolones
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:34
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Tidskriftsartikel (refereegranskat)abstract
- Vinylbenziodoxolones have recently been identified as efficient hypervalent iodine(III) reagents for electrophilic vinylations under transition metal-free conditions. Their unique reactivity allows synthesis of either internal or terminal alkenes, depending on the nucleophile class. This paper constitutes the first mechanistic investigation of VBX vinylations, and makes use of NMR studies, deuterium labelling and computations to rationalize the observed regio- and stereochemical outcome. Internal alkene formation in S-vinylation was found to proceed through the ligand coupling mechanism typical of diaryliodonium salts, whereas terminal alkene formation in P-vinylations took place via a phosphinous acid-coordinated VBX complex, which underwent concerted deprotonation and Michael-type addition. Subsequent base-assisted protonation and E2 elimination delivered the terminal alkene. The findings can be used to predict the regioselectivity in vinylations of other nucleophile classes.
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| 4. |
- Di Tommaso, Ester Maria, et al.
(författare)
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Ortho-Functionalization of Azobenzenes via Hypervalent Iodine Reagents
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Ortho-functionalized azobenzenes are much sought-after molecular switches. They may be tuned to absorb in the visible range of light and in many cases, the Z-isomers have very high thermal half-lives. However, methods to introduce substituents in ortho-position are still rare. This work presents the synthesis of azobenzenes with an iodine(III) moiety in the ortho-position. This novel class of diaryliodonium salts is demonstrated to efficiently arylate oxygen, nitrogen, carbon and sulfur nucleophiles under metal-free conditions. Selective transfer of the azobenzene moiety to the nucleophile gives access to an unprecedented range of ortho-substituted azobenzenes. In addition, the structure of these versatile reagents has been analyzed by X-ray crystallography and their photo-switching properties were investigated by NMR and UV-vis spectroscopy.
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| 5. |
- Di Tommaso, Ester Maria, et al.
(författare)
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ortho-Functionalization of azobenzenes via hypervalent iodine reagents
- 2023
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :34
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Tidskriftsartikel (refereegranskat)abstract
- ortho-Functionalized azobenzenes are much sought after molecular switches, as they may be tuned to absorb in the visible range of light and the (Z)-isomers can have high thermal half-lives. To enable straightforward access to these targets, we have developed a synthetic route via novel ortho-substituted azobenzene-functionalized diaryliodonium salts. Selective transfer of the azobenzene moiety to O-, N-, C- and S-nucleophiles under mild, transition metal-free conditions gives access to an unprecedented range of ortho-substituted azobenzenes. The photoswitching properties of the reagents were investigated and the structure was determined by X-ray crystallography.
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| 6. |
- Di Tommaso, Ester Maria, 1991-
(författare)
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Synthetic and Mechanistic Studies with Iodine(III) Reagents
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the development of metal-free transformations and mechanistic studies on the reactivity of two classes of hypervalent iodine reagents: diaryliodonium salts and vinylbenziodoxolones (VBX). Recently, they have been recognized as valuable synthetic reagents with broad applicability in organic synthesis. Moreover, hypervalent iodine reagents are non-toxic compounds and sustainable alternatives to heavy metals. In Chapter 1, an overview of hypervalent iodine(III) compounds is provided, with emphasis on the reagents that have been used in the thesis. First, the synthesis and general reactivity of diaryliodonium salts is described. Vinylbenziodoxolones are presented as a novel class of iodine(III) compounds that are powerful electrophilic vinylating reagents. Finally, a brief description of density functional theory and computational methods used in this thesis are outlined. The synthesis and applications of azobenzene-derived diaryliodonium salts is the topic of Chapter 2. The novel iodonium reagents were employed in chemoselective arylation reactions with a wide range of C, N, O and S-nucleophiles under mild and metal-free conditions. In Chapter 3, a mild and transition metal-free vinylation of thiols and mercapto heterocycles using vinylbenziodoxolones reagents is presented. The method allows the synthesis of a wide variety of S-vinylated products with complete chemo-, regio- and stereoselectivity. In Chapter 4, the first mechanistic investigation of VBX vinylations is presented. By exploiting the use of NMR analysis, deuterium labelling and DFT calculations, the observed regio- and stereochemical outcome of the vinylations of sulfur and phosphorous nucleophiles with VBX reagents has been rationalized. A transition metal-free, photocatalyzed C-vinylation method using VBX reagents is described in Chapter 5. The reactions proceed under mild conditions and the method tolerates a series of functional groups that lead to straightforward access to corresponding alkenes in good to high yields with high stereoselectivity.
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| 7. |
- Doobary, Sayad, 1995-, et al.
(författare)
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Structure-reactivity analysis of novel hypervalent iodine reagents in S-vinylation of thiols
- 2024
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Ingår i: Frontiers in Chemistry. - 2296-2646. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The transition-metal free S-vinylation of thiophenols by vinylbenziodoxolones (VBX) constituted an important step forward in hypervalent iodine-mediated vinylations, highlighting the difference to vinyliodonium salts and that the reaction outcome was influenced by the substitution pattern of the benziodoxolone core. In this study, we report several new classes of hypervalent iodine vinylation reagents; vinylbenziodazolones, vinylbenziodoxolonimine and vinyliodoxathiole dioxides. Their synthesis, structural and electronic properties are described and correlated to the S-vinylation outcome, shedding light on some interesting facets of these reagents.
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| 8. |
- Kumar, Bhaskar Pal, et al.
(författare)
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Photoredox-Catalyzed Stereoselective Vinylation Reactions with Vinylbenziodoxol(on)es
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have disclosed an efficient transition-metal-free radical-mediated C-C cross-coupling reaction of 4-alkyl-1,4-DHPs and VBXs through photo-redox catalysis to afford vinylated products in good yields with retention of configuration from parent VBXs. This mild photocatalysis system featured excellent functional group tolerance, a wide range of substrate scope and unique stereoselectivities. The utility of this new protocol has been demonstrated via the syntheses of diastereoselective C-vinyl glycosides. Preliminary mechanistic studies signify the involvement of radicals and the formation of ligand coupled TS in the reaction pathway.
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| 9. |
- Mondal, Shobhan, 1994-, et al.
(författare)
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Transition-Metal-Free Difunctionalization of Sulfur Nucleophiles
- 2023
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:8
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Tidskriftsartikel (refereegranskat)abstract
- Efficient protocols for accessing iodo-implanted diaryl and aryl(vinyl) sulfides have been developed using iodonium salts as reactive electrophilic arylation and vinylation reagents. The reactions take place under transition metal-free conditions, employing odorless and convenient sulfur reagents. A wide variety of functional groups are tolerated in the S-diarylation, leading to the regioselective late-stage application of several heterocycles and drug molecules under mild reaction conditions. A novel S-difunctionalization pathway was discovered using vinyliodonium salts, which proceeds under additive-free reaction conditions and grants excellent stereoselectivity in the synthesis of (aryl)vinyl sulfides. A one-pot strategy combining transition metal-free diarylation and subsequent reduction provided facile access to electron-rich thioanilines and a direct synthesis of a potential drug candidate derivative. The retained iodo group allows a wide array of further synthetic transformations. Mechanistic insights were elucidated by isolating the key intermediate, and the relevant energy profile was substantiated by DFT calculations.
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| 10. |
- Pal, Kumar Bhaskar, 1989-, et al.
(författare)
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Stereospecific Photoredox-Catalyzed Vinylations to Functionalized Alkenes and C-Glycosides
- 2023
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:20
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Tidskriftsartikel (refereegranskat)abstract
- We report an efficient radical-mediated C-C coupling through photoredox-catalyzed reactions of 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO). This transition-metal-free and mild photocatalytic method has excellent functional group tolerance and affords vinylated products in good yields, with complete retention of the alkene configuration. The utility of the methodology is demonstrated by the diastereoselective synthesis of C-vinyl glycosides. Preliminary mechanistic studies suggest that the C-C bond formation is stereospecific and proceeds through a concerted radical coupling transition state.
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