MECHANISMS OF HYDROLYSIS OF (TRIMETHYLSILYL) METHANESULFONYL CHLORIDE - SULFENE ENAMINE REACTIONS IN WATER

Kinetic, product analysis, and deuteration experiments are consistent with the following mechanisms of hydrolysis of (trimethylsilyl)methanesulfonyl chloride (1) (in 0.01 M KCl at 1-degrees-C): (a) pH less-than-or-equal-to 10.0, attack of water at silicon to form sulfene (5) which is trapped by water to give methanesulfonate anion (3), (b) pH greater-than-or-equal-to 10.0, attack of hydroxide anion (i) at silicon to yield sulfene (5) and (ii) at an alpha-hydrogen to form (trimethylsilyl)sulfene (4), in each case followed by trapping of the sulfene to give either methanesulfonate (3) or (trimethylsilyl)methanesulfonate (6) salts. Aqueous potassium fluoride catalyzes the hydrolysis of 1 with formation of the methanesulfonate 3, evidently by way of silicophilic attack of fluoride anion on 1 with formation of sulfene (5). Reaction of 1 with an enamine 7 in water (at pH 8 or 9), with or without fluoride, gives two characteristic sulfene-enamine products, (i) the four-membered cycloadduct 8 and (ii) the methylsulfonyl aldehyde 9. The same or related products are also obtained from methanesulfonyl, 2-propanesulfonyl, and phenylmethanesulfonyl chlorides and enamines in water (at pH 9). Hydrolysis of 1 is also catalyzed by aniline or triethylamine evidently giving 5.