(E)-2-Boryl 1,3-Dienes from the 10-TMS-9-BBDs: Highly Selective Reagents for the Asymmetric Synthesis of anti-α,β-Disubstituted β-Allenylamines from the Allylboration of Aldimines

The asymmetric allylboration of N-H aldimines with optically pure trans-4-substituted-2-boryl-1,3-dienes 6 is described. These organoboranes 6 serve as near-perfect asymmetric allylborating agents for N-H R aldimines for the preparation of anti-1,2-disubstituted-3,4-pentadien-1-amines 11 as essentially single diastereomers in enantiomerically pure form (>98% de, >= 98% ee). Enantiomerically pure cis-2,3-disubstitued piperidines 12 and alpha,beta-disubstituted-beta-amino acids 17 are readily prepared through the standard protocols. A novel Ru-catalyzed hydroamination provides trans-4,5-disubstituted-1-pyrrolines 21 from 11.