Stereochemistry of the Diels–Alder reaction at high pressure: diastereo- and enantioselective [4+2]cycloaddition of buta-1,3-diene to glyoxylic acid derivatives catalysed by (salen) chromium(III) complexes

High-pressure [4+2]cycloadditions of buta-1,3-diene 1 to chiral 2a–c and achiral 7a–c glyoxylates, in the presence of (salen) chromium(III) complexes 5 and 6, were studied. The influence of such chiral Lewis acids on diastereoselectivity or enantioselectivity of the cycloaddition was investigated; a moderate asymmetric induction for both diastereo- and enantioselective variants of the cycloaddition was observed (up to 58% de and up to 71% ee, respectively).

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