Rearrangement reactions leading to optically active α,α-disubstituted primary allylamines

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