The chemistry of N,N′-dimethylformamidine. II. Hydrolysis. Kinetically controlled formation of cis-N-methylformamide

The hydrolysis of N,N′-dimethylformamidine (DMFA) has been investigated in acid and alkaline aqueous media by 1 H nmr; only a narrow basic pH range could be extensively studied kinetically. The pseudo-first-order k obs rose steadily from pH 11.5 to 13.0 (reaction approximately first order in OH − ), then became independent of pH above 13.5 (9.3 × 10 −4 s −1 at 10 °C). In contrast to many amidines, DMFA is quite stable in acid solution (estimated value of the pseudo-first-order hydrolysis rate constant is 1.4 × 10 −1 s −1 at 10 °C, pH 0.05, from measurements at 100 and 140 °C). This stability is ascribed to the difficulty of eliminating the fairly strong base methylamine from the tetrahedral intermediate in acid solution.N-Methylformamide (NMF), one of the products, is formed initially as the cis isomer. A somewhat slower conversion then occurs to the thermodynamically more stable trans isomer. This unusual result is explained in terms of Deslongchamps and co-workers' theory of stereoelectronic control for the orbital-assisted breakdown of tetrahedral intermediates.