Improvement of the reactivity and selectivity of the oxo-Diels–Alder reaction by steric modification of the salen–chromium catalyst

Salen–chromium(III) complexes bearing sterically demanding substituents at the 3 and 3′ positions are applied for the oxo-Diels–Alder reaction of various aldehydes with Danishefsky’s diene. The readily-accessible complex bearing a bulky 3-phenylpent-3-yl substituent revealed its potential affording the cycloadducts with improved reactivity and excellent selectivities up to 96% ee, being considerably superior to the classic Jacobsen’s catalyst.