Styrylmalonates as an Alternative to Donor-Acceptor Cyclopropanes in the Reactions with Aldehydes: A Route to 5,6-Dihydropyran-2-ones.

A new strategy for modifying the reactivity of donor-acceptor cyclopropanes (DAC) has been suggested. It involves the use of isomeric styrylmalonates as alternative sources of reactive intermediates. The efficiency of the approach has been demonstrated in reactions with aromatic aldehydes. As a result, a new process for construction of the 5,6-dihydropyran-2-one skeleton has been developed. It efficiently occurs with high diastereoselectivity in the presence of BF3·Et2O; the products can be easily isolated by crystallization. The subsequent use of the resulting dihydropyranones in syntheses providing convenient access to various classes of compounds with broad molecular diversity has been demonstrated.