摘要:
Regioselectivity of the opening of 2,3-anhydrofuranosides 1 (alpha and beta) and 2 (alpha and beta) by dimethylamine (and by ammonia for 1) has been determined. Thermic stability of the eight corresponding vic-dimethylaminomesylates 11-14 (alpha and beta) in CD3CN and C6D6 has been studied by H-1 NMR : in each case steric hindrance seems to be the determinant factor of the four thermodynamic equilibria 11 reversible 12 (alpha and beta) and 13 reversible 14 (alpha and beta); aziridinium ions are assumed to be formed as intermediates and one of them has been effectively observed.