Brønsted Acid Assisted Regio‐ and Enantioselective Direct O‐Nitroso Aldol Reaction Catalysed by α,α‐Diphenylprolinol Trimethylsilyl Ether

Abstract

In the presence of p-nitrobenzoic acid, the O-nitroso aldol reaction of nitrosobenzene with enolisable aldehydes may be promoted by commercially available alpha,alpha-diphenylprolinol trimethylsilyl ether. The reaction proceeds with good yields and essentially complete enantioselectivity, with catalyst loadings in the 5-10 mol % range. The resulting alpha-oxyaldehyde adducts may be transformed in situ into alpha-oxyimines, which provide 1,2-amino alcohols upon treatment with Grignard reagents, in good overall yield (45-59%) and with typical diastereomeric ratios > or = 95:5.