On the alcohol- and water-catalyzed tautomerization of vitamins K1- and K2-derived quinone methide intermediates.

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 tautomerization 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.