Structure-reactivity analysis of novel hypervalent iodine reagents in -vinylation of thiols.

The transition-metal free -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 -vinylation outcome, shedding light on some interesting facets of these reagents.

-Functionalization of azobenzenes hypervalent iodine reagents.

-Functionalized azobenzenes are much sought after molecular switches, as they may be tuned to absorb in the visible range of light and the ()-isomers can have high thermal half-lives. To enable straightforward access to these targets, we have developed a synthetic route novel -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 -substituted azobenzenes.

Stereospecific Photoredox-Catalyzed Vinylations to Functionalized Alkenes and C-Glycosides.

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.

Transition-Metal-Free Difunctionalization of Sulfur Nucleophiles.

Efficient protocols for accessing iodo-substituted 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, enabling the regioselective late-stage application of several heterocycles and drug molecules under mild reaction conditions.

Electrophilic Vinylation of Thiols under Mild and Transition Metal-Free Conditions.

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.