“…Pathway C involves a concerted transfer of a hydride from DMAB to the carbonyl carbon atom . Theoretical calculations, for the hydroboration of carbonyls with ammonia borane in THF and methanol, have predicted a concerted double hydrogen atom transfer. , If this double hydrogen atom transfer was to occur with aqueous DMAB, we would expect to observe the cyclic dimer of dimethylamino-borane [(Me 2 N-BH 2 ) 2 ] in the 11 B NMR spectrum (δ 5, t, J = 114 Hz). , Additionally, this cyclic dimer has been shown to be an inactive reducing agent in the absence of a catalyst . Since the reduction of cyclohexanone with DMAB, in 3:1 stoichiometry, afforded cyclohexanol essentially quantitatively and no (Me 2 N-BH 2 ) 2 signal was observed in the 11 B NMR spectrum, it was concluded that the double hydrogen atom transfer was not a viable pathway for this aqueous reduction reaction.…”