An NHC-catalyzed annulation reaction of 3-halopropenals with
nitrosobenzene derivatives, providing access to 2,3-disubstituted
isoxazol-5(2H)-ones under mild conditions
is described. This procedure represents a metal-free approach to
the alternative equivalent of β-acylvinyl anions for the
formation of heterocyclic compounds.
carbenes - cyclization - heterocycles - tandem
reaction - umpolung