A Tin‐Free, Radical Photocatalyzed Addition to Vinyl Sulfones

Abstract

Radical conjugate addition onto vinyl sulfones was achieved by means of a convenient, tinfree procedure. This was based on the photocatalyzed C À H bond activation in aldehydes, amides, ethers and even cycloalkanes by using tetrabutylammonium decatungstate (TBADT). The reaction was likewise effective for the functionalization of b-substituted vinyl sulfones. The products are useful building blocks and were obtained in satisfactory yields both under artificial UV light and under sunlight, so demonstrating the "green" potential of the process.

Multi‐Step Continuous Flow Synthesis of β/γ‐Substituted Ketones

“…We envisaged that this reaction could be the starting point for the multi‐step continuous flow preparation of β‐substituted carbonyls of type I (Scheme 1b). The strategy relies on the photocatalyzed addition of aldehydes onto vinyl sulfones [6] to give β‐ketosulfones III . Base‐induced desulfonylation [7] to give enones II followed by reaction with a nucleophile (Nu − ) may give access to I with the overall formation of a C(=O)−C and C−Nu bonds.…”

Synthesis of quaternary centres by single electron reduction and alkylation of alkylsulfones

“…Organosulfones are versatile intermediates in organic synthesis because of the ease with which they permit facile structural modification through α-functionalization or conjugate addition. 1 Due to the inherent stability of sulfonyl groups, strong reducing agents such as Na amalgam and Mg are generally required for their removal ( Scheme 1 ). 2 However, a stepwise alkylative desulfonylation process would be much more valuable.…”

Organophotocatalytic dearomatization of indoles, pyrroles and benzo(thio)furans via a Giese-type transformation

“…Recent efforts on the study of photoredox catalysis under mild reaction conditions have made the process greener and more atom economical (Fig. 1b) [36][37][38][39][40][41][42][43][44][45][46][47] . In this process, the unsaturated C=C bond is transformed into a saturated C-C bond in a conjugate addition manner.…”

“…Nonetheless, the reversed reactivity of the addition of a nucleophilic radical to an electron-poor C 2 =C 3 bond of indoles is unknown. Moreover, even though incorporation of EWGs into the C 2 or C 3 positions of indoles could reverse the polarity from the innate nucleophilic to electrophilic system and serve as a potential radical acceptor, the weakly electron-deficient indoles render the Giese reaction more difficult because more electron deficient, less hindered α, β-unsaturated systems are generally used for effective nucleophilic radical addition [36][37][38][39][40][41][42][43][44][45][46][47] . Furthermore, in the photoredox process, possible oxidation of the weakly electron-deficient indole systems could complicate the process.…”