Enantioselective Conjugate Addition of Hydroxylamines to Pyrazolidinone Acrylamides
摘要:
[GRAPHICS]Chiral relay templates provide amplification of selectivity in conjugate addition reactions. Reversal of stereochemistry of the product isoxazolidinones has also been demonstrated by a simple change of the Lewis acid.
We report herein a successful example of an aza-[2,3]-Wittig rearrangement in an allylic tertiary N,N-dibenzyl amine derived from (S)-alaninol or (S)-isoleucinol. This reaction occurs upon metalation at the benzylic position with a mixture of butyllithium/diisopropylamine/potassium t-butoxide and proceeds with a high 1,3 transfer of chirality.
The selenyl triflate generated from the reaction of di-2-[(1S)-1-(methylthio)ethyl]phenyl diselenide with silver triflate reacts with various substituted O-allyl oximes to promote ring closure, which affords optically active isoxazolidines in high yields and with good diastereoselectivity (up to 93:7). Enantiomerically enriched 1,3-aminoalcohols can be easily obtained by NO bond cleavage of these
(1'S,4S)-2-Aryl-4-(1'-hydroxybenzyl)-4,5-dihydrooxazole as a Useful Chiral Auxiliary for the Synthesis of b-Amino Acids and b-Lactams in a Highly Stereoselective Manner
Enantioselective Conjugate Addition of Hydroxylamines to Pyrazolidinone Acrylamides
作者:Mukund P. Sibi、Mei Liu
DOI:10.1021/ol016807t
日期:2001.12.1
[GRAPHICS]Chiral relay templates provide amplification of selectivity in conjugate addition reactions. Reversal of stereochemistry of the product isoxazolidinones has also been demonstrated by a simple change of the Lewis acid.