Stereo- and regiospecific synthesis of unbranched alkenes and 1,4-alkadienes by meams of stabilised organocuprates

Lewis acid mediated reactions of organocopper reagents. A remarkably enhanced regioselective .gamma.-attack of allylic halides and direct alkylation of allylic alcohols via RCu.cntdot.BF3 system

“…),6'11 although isomerization, rearrangement, and formation of side products in many cases are reported.8•10•11 On the other hand, in the case of the reaction of allylic halides7 with organolithium and magnesium compounds, there are difficulties on the points of allylic transposition, geometrical isomerization, and cyclization.12-16 Several literature sources refer to prenyl halides, cyclic allylic halides, or branched allylic compounds in which cases the problem of partial rearrangement either does not exist or is overshadowed by attendant factors.4 •17-19 Recently it was reported that acyclic allylic halides undergo cross coupling at the a position via dialkylcuprate-MdS system. 20 The efforts to direct nucleophiles to the 7 position are relatively scarce. Although 7-unsubstituted allylic substrates undergo a facile 7-alkylation,10•21-23 the substitution appears to be controlled by steric factors.198-1 Recently exclusive syn 7-attack on the allylic system of 5-phenyI-2-cyclohexenylcarbamates was reported.…”