Catalytic Cleavage of C(<i>sp</i><sup>2</sup>)–C(<i>sp</i><sup>2</sup>) Bonds with Rh-Carbynoids
作者:Zhaofeng Wang、Liyin Jiang、Pau Sarró、Marcos G. Suero
DOI:10.1021/jacs.9b08632
日期:2019.10.2
We report a catalytic strategy that generates rhodium-carbynoids by selective diazo activation of designed carbyne sources. We found that rhodium-carbynoid species provoke C(sp2)-C(sp2) bond scission in alkenes by inserting a monovalent carbon unit between both sp2-hybridized carbons. This skeletal remodeling process access synthetically useful allyl cation intermediates that conduct to valuable allylic
2-Methylene-4-butyrolactones were conveniently synthesized by treatment of an aldehyde with 2-carboethoxyallyl(-ic) bromide and metallic tin (and aluminum) in good yields. Protolichesterinic acid was synthesized by employing the method.
Stable organozinc compounds derived from alkyl-3-alkyl-2-(bromomethyl)-proenoates have been prepared. NMR 13C, 1H and IR stidies show only one Z stereoisomer (no methylenic form) with a strong chelation between zinc and the carbonyl oxygen of the ester and solvated by only one solvent molecule. Hydrolysis can be achieved by two concurrent mechanisms with or without transposition.
Stable organozinc compounds derived from alkyl 3-alkyl 2-(bromomethyl) propenoates reacted with ketones and aldehydes to give alpha-methylene gamma-butyrolactones in excellent yields. Different reaction parameters were studied and some transition states were proposed.