Diarylbis(acylamino)spiro-λ4-sulfanes and cyclic acylaminosulfonium salts. A kinetic study of equilibrium and hydrolysis reactions

摘要: Kinetics for the hydrolysis of diarylbis(acylamino)spiro-λ4-sulfanes 3a–e and 9 precursor acylaminosulfonium salts 5a–e 8 both leading to sulfoxides 6a–e 10, respectively, have been studied under pseudo-first-order conditions in dioxane–water mixtures. Medium, substituent (ρ+ –0.44) solvent isotope effects (kH2O/kD2O ≈2) indicate that cleavage one S–N bonds a simultaneous proton-transfer from H2O leaving carbamoyl group take place rate-determining step spiro-λ4-sulfanes 3a–e. The OH– ion intermediates formed together are converted fast steps. shows deviation first-order kinetics at starting period reaction, which may be ascribed an equilibrium formation spiro-λ4-sulfanes. between 3a 5a has by spectroscopic methods, K35 5 × 10–7 mol dm–3 was obtained 70:30 (v/v) dioxane–water, 25 °C. is shifted towards as acidity increases with progress hydrolysis, or when acid added mixture. In case medium, deuterium ≈4.3) well general base catalytic effect acetate ions suggest nucleophilic attack water on sulfonium centre occurs OH hydroxy(acylamino)-λ4-sulfane. Acylaminosulfonium salt 12, having sterically hindered reaction centre, undergoes only more ions. Relative reactivities different ring-size observed bis(acyloxy)-, (acyloxy)(acylamino)- bis(acylamino)-spiro-λ4-sulfanes cyclic compared interpreted.