Nickel-catalyzed multi-component connection reaction of isoprene, aldimines (lactamines), and diphenylzinc

Ni(acac)₂ catalyzes the four-component connection reaction of diphenylzinc, isoprene, aromatic aldehydes, and aromatic amines in this order and provides stereochemically homogeneous (E)-1-arylamino-1-aryl-3-methyl-5-phenyl-3-pentenes (1) in excellent yields. Aliphatic aldehydes react similarly and give (E)-1-arylamino-1-alkyl-3-methyl-5-phenyl-3-pentenes (1) in slightly reduced yields. When the alkyl groups are bulky, in addition to 1 are formed (E)-1-arylamino-1-alkyl-4-methyl-5-phenyl-3-pentenes (1′) as the minor products. Lactamines prepared in situ from five- and six-membered lactols and aromatic amines are more reactive than alkyl aldehyde aldimines and furnish (E)-4-arylamino-6-methyl-8-phenyl-6-octen-1-ols (4) and (E)-5-arylamino-7-methyl-9- phenyl-7-nonen-1-ols (5), respectively, in good yields with excellent E-stereoselectivity.