Issue 20, 2000

Studies on the asymmetric reduction of β-oximino methyl etherboronates: reagent control, double diastereocontrol and transmitted remote asymmetric induction

Abstract

High asymmetric induction (94% ee) could be obtained in the reduction of the achiral E-oxime ether boronate 5 with a homochiral oxazaborolidine 13–BH3–THF complex. Application of this homochiral reducing agent system to non-aromatic oxime ethers 21 produced low to moderate asymmetric induction. Application of the same homochiral reducing agent system to reduction of homochiral boronate E-oximes 3 and 4 produced extreme double diastereoselection effects, i.e. 8 and 95% ee respectively, which demonstrated that remote asymmetry was being ‘transmitted’ by a suitable choice of a ‘partner’ molecule from the boronate moiety to the oxime during reduction. However, attempts to obtain direct remote asymmetric induction in the reduction of homochiral β-oximino boronate methyl ethers 3 and 4 to the corresponding amines produced zero, with for example BH3–THF complex, up to 28% ee with an Et3N–BH3–THF mixture (after oxidative boronate ester cleavage).

Article information

Article type
Paper
Submitted
19 Jul 2000
Accepted
24 Aug 2000
First published
03 Oct 2000

J. Chem. Soc., Perkin Trans. 1, 2000, 3362-3374

Studies on the asymmetric reduction of β-oximino methyl ether boronates: reagent control, double diastereocontrol and transmitted remote asymmetric induction

H. E. Sailes, J. P. Watts and A. Whiting, J. Chem. Soc., Perkin Trans. 1, 2000, 3362 DOI: 10.1039/B005837H

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