31P NMR assays for rapid determination of enantiomeric excess in catalytic hydrosilylations and transfer hydrogenations

Abstract

Chiral chlorophosphine (S)-(1,1′-binaphthalen-2,2′-dioxy)chlorophosphine (S)-2 was tested for its performance as a chiral-derivatizing agent (CDA) using solutions of various alcohols, amines, and N-BOC amino acids. Based on 31P NMR spectroscopy, the enantiomeric excess was determined within less than 5 min per sample, reaching an accuracy of ±1%. One-pot procedures for a combination of the method with typical homogenous catalytic transformations of prochiral ketones were established. Hydrosilylation products may be analyzed after conversion into alcohols using HF bound to PS-vinyl pyridine co-polymer beads. Transfer hydrogenations simply require solvent evaporation prior to the use of the CDA. © 2009 Elsevier Ltd. All rights reserved.