Visible-Light-Initiated Na₂-Eosin Y Catalyzed Highly Regio- and Stereoselective Difunctionalization of Alkynes with Alkyl Bromides

Abstract

A highly regioselective and stereoselective addition of alkyl bromides (amino-brominated aromatic β,β-dicyanoalkenes) to arylacetylenes by photoredox catalysis was developed. This difunctionalization of arylacetylenes was accomplished under ambient and metal-free conditions to produce alkenyl bromides in high efficiency with a wide range of group tolerance.

Cu(I)-Catalyzed C–H Alkenylation of Tertiary C(sp3)–H Bonds of 3-Aryl Benzofuran-2(3H)-ones to Give Z- and E-Styrene Containing Quaternary Carbon Centers with 99/1 Regioselectivity

“…Based on the above results and those reported in the literature, , two possible pathways for these two reactions are proposed (Scheme ). For the reaction involving phenylacetylene, the radical intermediate A is first generated from benzofuranones ( 1a ) in the presence of CuCl and DTBP.…”

Visible light promoted difunctionalization reactions of alkynes

“…Very recently, the synthesis of spiro [4,5] deca-1,6,9 trieno-8-ones was also reported by Zhang and co-workers, with 2-bromo-1,3-dicarbonyl derivatives as the activated halide [93]. It should be noted that 2-bromo-malononitriles could also be utilized in visible light promoted difunctionalization of alkynes, which was explored by Wang and Meng in 2016 [94].…”

Eosin Y mediated photo-catalytic C–H functionalization: C–C and C–S bond formation

“…This reaction gives an atom-economical and efficient approach towards a bifunctional motif with a broad substrate scope. 50 In this approach, the photocatalyst was excited under visible light and oxidatively quenched with 106 to give [Na 2 –eosin Y] + and radical intermediate A , which underwent regioselective addition to alkynes and the formation of intermediate B . Vinyl carbocation C was obtained by oxidation of intermediate B which reacted with bromide anions and gave the final product vinyl bromides ( 108 ) (Scheme 51).…”