Hydrolysis Rates of Saturated Acyclic and Cyclic Sulfinamides: X-ray Crystal Structures of an Acyclic Sulfinamide and γ-Ammoniopropanesulfinate

Article abstract of DOI:10.1021/jo00311a010

The rates of the neutral hydrolysis of a saturated acyclic sulfinamide, N,N-dimethylmethanesulfinamide (CH3S(O)N(CH3)2), the monocyclic compounds (isothiazolidine 1-oxide, 2-(1-phenylethyl)isothiazolidine 1-oxide, tetrahydrothiazine 1-oxide) and the bicyclic compounds (9-thia-1-azabicyclo<4.3.0>nonane 9-oxide and 2-thia-1-azabicyclo<4.3.0>nonane 2-oxide) were determined in D2O using 1H NMR at 65 deg C.The first-order rate constants are similar to those of β-lactams.Activation parameters were determined for the acyclic, one cyclic, and one bicyclic sulfinamide.The striking feature which arises is that the parameters for the hydrolysis of the acyclic sulfinamide (ΔH(excit.) = 11 +/- 4 kcal mol^-1; ΔS(excit.) = -47 +/- 11 cal mol^-1 K^-1) are much different from both the monocyclic sulfinamide and the bicyclic sulfinamide (ΔH (excit.) ca. 23 +/- 2 kcal/mol^-1; ΔS(excit.) ca. -15 +/- 4 cal mol^-1 K^-1, respectively).As a consequence, the acyclic sulfinamide hydrolyzes about 25 times faster than the cyclic sulfinamides.Most other heterocyclic compounds hydrolyze more rapidly than their acyclic analogues.Thus, the factors influencing the relative rates of hydrolysis of sulfinamides appear to be acting in a unique manner.The X-ray crystal structure of the first simple sulfinamide, N-(1-phenylethyl)methanesulfinamide, and a zwitterionic ammoniosulfinate, 3-((1-phenylethyl)ammonio)propanesulfinate, are also reported.