LOW-TEMPERATURE PHOTO-CHEMICAL MATRIX APOSYNTHESIS OF AN OXATHIETE AND ITS VALENCE TAUTOMERISM WITH THE CORRESPONDING ALPHA-KETOTHIONE

Photochemical elimination of carbon monoxide from 5-methyM, 3-benzoxathiol-2-one (5b) yields the transient monothio-o-benzoquinone 6b. This, at 77 K, can be reversibly photoisomerized into a species identified as thebenzoxathiete 7b containing the previously unobserved oxathiete ring. When 5b is irradiated in ethyl vinyl ether at room temperature, trapping occurs regiospecifically to give the adduct 11a, which then undergoes a photochemical rearrangement to yield 12. Spectroscopic evidence suggests that the transients may experience a second elimination of carbon monoxide to give the cyclopentadienethione 9a. Monothiobenzil (lb) and monothiopivalovl (la) do not appear to undergo an analogous photoisomerization to give the corresponding oxathietes. l, 3-Benzodithiol-2-one(5e) also loses carbon monoxide photochemically to give a transient identified as benzodithiete (7e), which can be trapped by dimethyl acetylenedicarboxylate. © 1979, American Chemical Society. All rights reserved.