A New Tandem Cross Metathesis–Intramolecular Aza-Michael Reaction for the Synthesis of α,α-Difluorinated Lactams

Abstract

A new tandem cross metathesis–intramolecular aza-Michael­ reaction in which an α,α-difluorinated amide serves as a source of nucleophilic nitrogen is described. This process gives rise to a new family of fluorinated γ- and δ-lactams. The tandem protocol is catalyzed by the Hoveyda–Grubbs second-generation ruthenium catalyst with titanium(IV) tetraisopropoxide as a co-catalyst and it is highly efficient when conjugated ketones are used as the Michael acceptors. With conjugated esters, however, it is necessary to perform a step-by-step procedure in which the cyclization event is activated by the addition of a base. An asymmetric version of the process is also evaluated.

Key words

Michael additions - tandem reactions - catalysis - heterocycles - fluorine - amides - asymmetric catalysis

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