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.