Phosphine-Promoted Tandem Intermolecular Diels-Alder Reactions with Pentadienyl 4-Nitrobenzoate as a Diene Precursor

摘要

A phosphine-promoted tandem Diels-Alder reaction using pentadienyl 4-nitrobenzoate (a-vinyl MBH adduct) as a diene precursor with 3-olefinic oxindoles or CF3-activated ketones as dienophiles has been developed. The reaction proceeds through the formation of a pentadienyl phosphonium intermediate via S(N)2?addition, which acts as both a D-A diene and a precursor for the exomethylene moiety. This method offers a metal-free and step-efficient approach for synthesizing exomethylene-bearing spirooxindoles and dihydropyrans, which are privileged structures found in natural products.

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