On the Alcohol- and Water-Catalyzed Tautomerization of Vitamins K_1- and K_2-Derived Quinone Methide Intermediates

摘要

Rates of conversion of 1,3-quinone methides into the corresponding 1,2-quinone methide tautomers, formed upon laser-flash excitation of vitamins K_1 and K_2 in CH_3-CN solutions, were determined in the presence of hydroxylic solvents (ROH; R = H, alkyl). In all cases, the tautomer-ization process is accelerated in the presence of ROH, and the corresponding observed rate constants show a cubed dependence on ROH concentration. This high-order dependency is attributed to a proton-relay transfer involving 3 equiv of ROH in each case.