Micellar effects upon the hydrogen ion and general acid catalyzed hydration of 1,4-Dihydropyridines

Abstract

The rate limiting step in the hydration of 1-benzyl-l, 4 — dihydronicotinamide (1a) and 1-benzyl-3-acetyl-l, 4- dihydropyridine (.lb) is; a slow proton transfer, as shown by the kinetic deuterium solvent isotope effects and buffer catalysis. Reactions in dilute HC1 are strongly inhibited by cationic micelles of cetyltrimethylammonium bromide, CTABr, and the inhibition can be related to the micellar binding of the substrates determined spectrophotometrically or by solubility. Anionic micelles of sodium lauryl sulfate, NaLS, only weakly catalyze hydration in dilute HC1, and rate constants go through maxima with increasing [NaLS].