Enolizable Carbonyls and N,O-Acetals A Rational Approach for Room-Temperature Lewis Superacid-Catalyzed Direct α-Amidoalkylation of Ketones and Aldehydes
Résumé
An efficient catalytic room-temperature direct α-amidoalkylation of carbonyl donors, that is, ketones and aldehydes with unbiased N,O-acetals, is described. Sn(NTf2)4 is an optimal catalyst to promote this challenging transformation at low loading and the reaction shows promising scope. A comprehensive and rational evaluation of this reaction has led to the establishment of an empirical scale of nucleophilic reactivity for a broad set of ketones that should be helpful in the synthetic design and development of carbonyl α-functionalization methods. Magic Lewis superacid A room-temperature catalytic direct α-amidoalkylation reaction of ketones and aldehydes that operates via N-acyliminium ions generated in situ is reported (see scheme). This reaction is efficiently catalyzed by 0.5-2 mol % of the Lewis superacid Sn(NTf2)4 and exhibits a large scope. An evaluation of this Mannich coupling led to the establishment of a reactivity scale of enolizable ketones. © 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.