posted on 2016-06-09, 15:37authored byRamani Gurubrahamam, Yan ming Chen, Wan-Yun Huang, Yu-Te Chan, Hsiang-Kai Chang, Ming-Kang Tsai, Kwunmin Chen
Kinetic resolution
of nitroallylic amines was established using
chiral α,α-l-diphenylprolinol silyl ether auxiliary
through isolation of the dihydrooxazine N-oxide intermediates.
Further hydrolyzing the resting states provided tetrahydropyridines
in high chemical yields and high to excellent stereoselectivities
(up to >20:1 dr and 98% ee). A detailed mechanistic explanation
for
stereoselective protonation in the dihydrooxazine was probed computationally.
In addition, the probable intermediates in α-halogenation of
aldehydes (masked with enamines) were isolated to provide crystallographic
evidence.