1 research outputs found
External Electric Field Induces a Mechanistic Crossover in the Reactivity of 1,3-Dienes with Sulfur Dioxide: Sulfolene <i>Versus</i> Sultine
1,3-Dienes (1) react with SO2 to produce
sulfolenes (2) and sultines (3). Previous
experiments and computational studies have shown that hetero-Diels–Alder
(HDA) reaction producing the sultine is kinetically favorable compared
to the chelotropic (CE) reaction producing the sulfolene. In this
article, DFT calculations for a series of substituted 1,3-dienes show
that under the influence of a moderate oriented external electric
field (OEEF) of 2.0–4.0 V nm–1 along the
reaction axis, the chelotropic reaction becomes the kinetically favorable
reaction. In the absence of the OEEF, the destabilizing distortion
involved in bringing the 1,3-diene and SO2 to the CE transition-state
(TS) exceeds than for the HDA TS. However, under the influence of
the OEEF, the strongly stabilizing electrostatic interactions in the
CE TS effectively overcome the structural distortion energy. The enhanced
dipole moment of the CE TS vis-à-vis the HDA TS under the OEEF
accounts for the stabilization of the former