An asymmetric cascade reaction between β-keto acylpyrazoles and o-quinone methides in a formal [4 + 2] fashion to access potentially pharmacological active trans-3,4-dihydrocoumarins has been achieved efficiently by using a quinine-based chiral squaramide as the catalyst. The desired products were obtained in high yields with excellent diastereo- and enantioselectivities (up to 96% yield, >19/1 dr and 96% ee) under mild reaction conditions.
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