DECOMPOSITION OF THIIRANE 1,1-DIOXIDES (EPISULFONES)

The first-order rates of decomposition of the episulfones, 2-phenylthiirane 1,1-dioxide (1), trans-2,3-diphenylthiirane 1,1-dioxide (2), and cw-2,3-diphenylthiirane 1,1-dioxide (3) (to alkene and sulfur dioxide), were found to correlate surprisingly well with the ionizing power of the medium. The rates were found to be accelerated by alkoxide ion and were first order in alkoxide ion when the concentration was sufficiently high. Solvolytic decomposition of 2 gave ?trans-stilbene stereospecifically and 3 gave cis-stilbene stereospecifically, but trans-stilbene was obtained from 3, as well as from 2, when alkoxide ion was present. Deuterium exchange experiments showed that in the presence of methoxide ion 3 underwent exchange, with retention of configuration, at a rate considerably faster than its rate of epimerization to 2. The solvolytic decompositions of 1-3 are represented as occurring by way of diradicai intermediates; a diradicai anion intermediate is assumed for the alkoxide ion promoted reactions. The latter reaction is believed to involve addition of methoxide ion to the sulfone grouping. © 1968, American Chemical Society. All rights reserved.