(E)-2-boryl 1,3-dienes from the 10-TMS-9-BBDs: highly selective reagents for the asymmetric synthesis of anti-α,ß-disubstituted ß-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 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 α,ß-disubstituted-ß-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.

(E)-2-boryl-1,3-butadiene derivatives of the 10-TMS-9-BBDs: highly selective reagents for the asymmetric synthesis of anti-1,2-disubstituted 3,4-pentadien-1-ols.

The efficient stepwise construction of optically pure trans-4-substituted 2-boryl-1,3-butadienes 6 is described. Hydroboration of 1-alkynes with either enantiomeric form of 3 leads to the pure trans-1-alkenylboranes 4 which undergo addition of alpha-ethoxyvinyllithium followed by a BF(3)-mediated 1,2-B-->C vinylic group migration to provide 6. These organoboranes 6 serve as a new type of asymmetric allylborating agent providing an extremely selective protocol for the preparation of anti-1,2-disubstituted 3,4-pentadien-1-ols 8 as essentially single diastereomers in enantiomerically pure form. One example of a cis-2-boryl-1,3-butadiene (9) was prepared through a Grignard procedure. It was found to provide the corresponding syn-alcohol 11. The utility of 8 was demonstrated in their conversion to substituted beta-hydroxy acids 12 through ozonolysis and to substituted alpha,beta-unsaturated-delta-lactones 13 through Ru-catalyzed cyclocarbonylation.