ANALYSIS OF THE DIASTEREOSELECTIVITY OF SULFINATE FORMATION IN THE OXIDATION OF SEC-ALKYL 4-NITROBENZENESULFENATES WITH SINGLET OXYGEN AND M-CHLOROPERBENZOIC ACID AND SULFINATE VERSUS SULFONATE FORMATION IN THE SINGLET OXYGEN OXIDATION OF THE ALKYL 4-NITROBENZENESULFENATES

The diastereoselectivities in the self-photoinduced single oxygen and m-chloroperbenzoic acid oxidations of two series of sec-alkyl 4-nitrob enzenesulfenates to the corresponding 4-nitrobenzenesulfinates have be en measured. The diastereoselectivities are only moderate but show som e interesting trends with the nature and size of the functions in the arkyl group. Sulfonate formation also occurs, the extent of which incr eases with increasing size of the substituents in the alkyl group. The sulfonates are not formed by the further oxidation of the sulfinates. A mechanism for the formation of the sulfinates and sulfonates is pro posed that involves the initial formation of a peroxysulfoxide interme diate which, when sterically unencumbered, can react with the starting sulfenate to generate two molecules of sulfinate but, when sterically encumbered, undergoes ring closure to form an alkoxythiadioxirane int ermediate which can react with the starting sulfenate or undergo ring opening to produce the sulfonate. The effect of the incursion of other reactions on the relative yields of the sulfinates and sulfonates is also discussed.