NHC Brønsted base-catalyzed transformations of isochromene derivatives: regulation of products by the structures of carbene catalysts.

Two different transformations of α-(isochromen-1-yl)ketones catalyzed by NHC Brønsted bases are reported. In the presence of a triazole carbene, α-(isochromen-1-yl)ketones isomerized into β-(2-(aroylmethylene)phenyl)-α,β-unsaturated ketones in 38-88% yields, while the same reaction catalyzed by an imidazole carbene produced 1-aroylnaphthalene derivatives in 90-99% yields. This work not only provides a new method for the synthesis of a novel type of α,β-unsaturated ketone and multi-substituted naphthalene derivatives, but also advances the application of NHC catalysts in the field of Brønsted base-catalysis.