Catalytic Nazarov reaction of aryl vinyl ketones via binary acid strategy.

We describe herein a viable binary acid strategy for the catalytic Nazarov reaction of aryl vinyl ketones. Simply combining a Lewis acid and a Brønsted acid led to a dramatic enhancement of the catalytic activity in the Nazarov reaction of aryl vinyl β-ketoesters. The obtained optimal binary acid catalyst In(OTf)(3)/diphenyl phosphoric acid (DPP) can be applied to a range of aryl vinyl ketones with good activity. A trend of reactivity has also been summarized on the basis of mapping of the substituents.