Organo-photoredox-catalyzed atom-transfer radical substitution of alkenes with α-carbonyl alkyl halides
A light-driven atom-transfer radical substitution (ATRS) and carboesterification reaction of alkenes with alkyl halides has been developed using PTH as the organo-photoredox catalyst. Two types of products were obtained, depending on the additive and solvent used during the reaction. Primary, secondary, and tertiary alkyl halides reacted to give the ATRS products. This protocol has several advantages: it requires mild reaction conditions and a low catalyst loading and exhibits a broad substrate scope and good functional group tolerance. Mechanistic studies indicate that alkyl radicals might be generated as the key intermediates via photocatalysis, providing a new direction for ATRS reactions.
Nishikata, Takashi,Hirata, Goki,Shimada, Taisei
supporting information
p. 8952 - 8956
(2020/12/02)
Tandem Reactions Enable Trans- and Cis-Hydro-Tertiary-Alkylations Catalyzed by a Copper Salt
A methodology to synthesize trans- and cis-alkenes via well-controlled hydroalkylation of alkyl radicals to alkynes is reported. α-Bromocarbonyl compounds are useful alkyl radical precursors in the presence of Cu(I) catalysts. Under copper catalyst conditions and in the presence of silane or alcohol/B2pin2, trans- and cis-hydroalkylation occurred with excellent stereoselectivities. The judicious choice of additives allowed for this stereodivergence, giving selective access to the trans-alkylated alkenes with HSiTMS3 and cis-alkylated alkenes with t-BuOH/B2pin2 in good yields with selectivities.
Nakamura, Kimiaki,Nishikata, Takashi
p. 1049 - 1052
(2017/08/09)
Nickel-catalyzed heck-type alkenylation of secondary and tertiary α-carbonyl alkyl bromides
Ni made it! A novel Heck-type reaction of secondary and tertiary α-carbonyl alkyl bromides, most likely involving a radical process, was achieved through the use of a nickel catalyst. Various substituted styrenes and 1,1-diaryl alkenes were utilized as substrates to easily construct α-alkenyl carbonyl compounds with tertiary or quaternary carbon centers. A catalytic cycle involving NiI/NiII is proposed based on our experimental results. EWG=electron-withdrawing group.