Rearrangement and substitution of pentadienyl groups in homopentadienylamines on treatment with organolithium reagents

(4R, 5R)-N,N ' -Bis[(1S)-1-phenylethyl]-3,6-divinyl-1,7-octadiene-4,5-diami ne under-went rearrangement and/or substitution of one/two pentadienyl grou ps on treatment with 2-4 equiv. of an organolithium reagent (nBuLi, PhLi) i n THR By careful choice of experimental conditions, C-1- or C-2-symmetric 1 ,2-disubstituted 1,2-diamines could generally be obtained with good stereoc ontrol. It is proposed that the reaction proceeds through competitive pathw ays involving a 1,3-shift of the branched homopentadienyllithium amide moie ty with retention of configuration and retro-pentadienyllithiation to form an intermediate imine. In contrast, only rearrangement was observed on trea tment of (1R,S)-N-[(1S)-1-phenylethyl]-1-(2-pyridyl)-2-vinyl-3-butenylamine with 2 equiv. of nBuLi at -78 degreesC.