Rearrangement Reactions Leading to Optically Active α,α-Disubstituted Primary Allylamines

Synthetic routes to alpha, alpha-disubstituted allylamines have been examined. Racemic compounds were conveniently prepared by thermal Overman rearrangements of primary allylic alcohols with trisubstituted double bonds, but rearrangement of these substrates using the only commercially available compound known to catalyze enantioselective Overman rearrangements, the cobalt oxazoline palladacycle (R)-COP-Cl, failed. Instead, optically active secondary allylic alcohols with trisubstituted double bonds, obtained by Corey-Bakshi-Shibata reduction of the corresponding methyl ketones, were synthesized and converted into alpha,alpha-disubstituted allylamines through a thermal Overman rearrangement or an allylic-cyanate-to-isocyanate rearrangement. High chirality transfer (90-99 %) was obtained for both reaction sequences, but the yields were greatly improved when the allylic-cyanate-to-isocyanate rearrangement was used.