1,4-Additions of the highly functionalized copper reagents RCu(CN)ZnI · 2 BFP₃ to trisubstituted enones. A new BF₃ promoted cyclization reaction

The new copper reagents RCu(CN)Zn I · 2 BF₃ 1 containing various functional groups like esters, cyanides, chlorides or enoates react with β, β′- disubstituted enones to afford the Michael adducts 4-7 in high yields (81-98%). Cyano-substituted 1,4-adducts undergo a new cyclization reaction leading to the very stable bicyclic difluoroboron enolates 11a-11c which could be converted into the bicyclic diketones 12 under mild basic conditions. The X-ray structure of 11b is reported.