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1.11.11.2 Formation of syn-Stereotriads by Aldol Coupling of Vinyl Ketones and α-Amino Aldehydes

DOI: 10.1055/sos-SD-201-00267

Schleicher, K. D.; Jamison, T. F.Science of Synthesis: Stereoselective Synthesis, (20111561.

In the related reductive aldol coupling of methyl or ethyl vinyl ketone with chiral α-amino aldehydes 62, very good selectivity is observed for the formation of the all-syn-stereotriad 63A (Scheme 36).[‌45‌] More rigorously, the major compound obtained is the syn-aldol, anti-FelkinAnh product. The monoprotection of the α-amino group of the aldehyde is crucial for this selectivity, as hydrogen bonding between the NH and the aldehyde carbonyl is suggested to play a key role in directing the anti-FelkinAnh selectivity as well as enhancing aldehyde reactivity through stabilization of the alkoxide in the transition state. By way of comparison, the N-(tert-butoxycarbonyl)-N-methylamino aldehyde affords the syn-aldol, FelkinAnh product in low yield in the reaction with methyl vinyl ketone.

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