The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxide has been examined. In contrast to the analogous sulfones these sulfoxides undergo a variety of photochemical rearrangements. At least three distinct pathways have been recognized; β-hydrogen abstraction or rearrangement to cyclic sulfenates, which then undergo further reaction by homolysis of the S—O bond, appearing to be particularly favorable processes. In a small number of examples, photochemical deoxygenation is observed as a competing reaction. Mechanisms which attempt to account for the influence of structural variations on the particular pathway followed have been proposed.

that of the lowest polysulfide (3, m = 3.5). The latter had its strongest band centered at ~1000 cm"1 in common with the diand trisulfide (3, m = 2,3);16 this band became inconspicuous when m exceeded 3. Hence 3 (m = 3.5) evidently contained considerable trisulfide. Astonishingly, all of the polysulfide spectra showed strong bands at 1230-1120 and 1080-1025 cm"1 characteristic of sulfonate salts.9 The extreme improbability that significant oxidation had occurred of S02Na to S03Na, however, followed from several facts: (a) presence of such bands in the analytically pure trisulfide 3 (m = 3) but not in the disulfide;16 (b) the improbability of equivalent oxidation that would produce congruent polysulfide (disulfinate) spectra; (c) the lack of exposure to 02 or oxidants (Ar-purged solvents, Ar atmosphere), together with the short time from the beginning of reaction to the final product (<6 h); (d) resistance to oxidation of aqueous solutions of the disulfinate 3 (m = 3) under ambient conditions in excess of 1 week (Table I); (e) the facile loss of sulfur (cf. Scheme II), which contrasts with the stability of a sulfonate disulfide (AcNHlCHp^SfCH^SOjNa; trace of disproportionation to symmetrical disulfides in 96 h at 61 °C) but accords with that of a sulfinate disulfide (AcNH-(CH2)2SS(CH2)4S02Na; ~50% disproportionation in 0.5 h at 61 °C).h Nevertheless, for certainty, the identity of 3 (m = 4.9) as a sulfinate was confirmed in two ways, (a) An aqueous solution of 3 (m = 4.9) was treated with 6 equiv of 30% aqueous H202 and a trace of HC1, allowed to stand for 1 h, neutralized, and freeze-dried. Absence of the strong band at 1070 cm'1 in this resulting solid showed oxidation of S02Na to S03Na and confirmed assignment of the band at 1070 cm"1 to S02Na; loss of the band at 1020 cm'1 appeared to occur but was less clear. Strong bands appeared in the product at 1230-1120 and 1090 cm"1, as expected for S03Na.9 (b) Reflux of 3 (m = 4.9) with 2 equiv of 2,4-dinitrochlorobenzene for 3 h in EtOH led to a yellow precipitate having the strong bands characteristic of a nitrosulfone [1530-1500 (N02), 1360-1320 (3 bands; N02, S02), 1140 cm"1 (S02)].12 Absence again of the 1070-cm"1 band of 3 (m = 4.9), through conversion of S02Na to S02Ar(N02)2, confirmed the assignment to S02Na; the 1180-cm"1 band also had disappeared and perhaps also that at 1020 cm'1. Hence the IR bands for polythiobis(butanesulfinates) include that at 1070 cm"1 and perhaps 1180 and/or 1020 cm"1.

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