Dihydrooxazine N-Oxide Intermediates as Resting States in Organocatalytic Kinetic Resolution of Functionalized
Ramani Gurubrahamam1, Yan Ming Chen1, Wan-Yun Huang1
1Department of Chemistry, National Taiwan Normal University , Taipei 11677, Taiwan R.O.C.
Abstract:
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.
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