The effect of solvation in torquoselectivity: ring opening of monosubstituted cyclobutenes

Abstract

The paradigmatic electrocyclic ring opening of monosubstituted cyclobutenes has been used to diagnose possible solvation effects tuning the torquoselectivity observed in these reactions. This kind of selectivity in electrocyclic reactions is mostly due to strong orbital interactions, particularly when they involve powerful electron donors and acceptors, which also combine with usually milder steric effects. Orbital interactions are established between the cleaving C–C bond and the HOMO/LUMO of the EDG/EWG substituent. This implies that the larger torquoselectivity-featuring substrates may also suffer stronger solvation effects due to the higher polarity imposed by the substituent. This premise is tested and the source of solvation effects as a consequence of substitution analyzed.