Rates and Equilibria of the Reactions of 2,6-Di-t-butyl-4-phenyl- and 2,6-Diphenyl-4-t-butyl-thiopyrylium Ions with Butylamine in DMSO

Both the title cations react with butylamine in DMSO at 25 oc to yield, under kinetic control, the corresponding 2H and 4H adducts, which successively equilibrate to give the thermodynamically more stable 2H adduct. The results indicate that the significant increase of steric hindrance on the reaction centres, obtained by replacing the phenyl group with the t-butyl one, does not cause a change in the rate-controlling step, in contrast with the behaviour previously observed when the steric hindrance of the attacking amine was increased.