Substrate-Specific Reduction Mechanisms for NADH Models. Reduction of N-Methylacridinium Iodide and α,α,α-Trifluoroacetophenone

Article abstract of DOI:10.1021/jo00243a010

The reduction of α,α,α-trifluoroacetophenone by five N-substituted dihydronicotinamides (DHNAs) proceeds by a free radical chain process initiated by single electron transfer (SET).In dry acetonitrile the chain, whose propagation chain steps contain a SET-hydrogen atom transfer sequence, could be inhibited with m-dinitrobenzene or initiated by AIBN.Under the same reduction conditions methylacridinium iodide does not undergo homolytic chain reduction.The reduction of methylacridinium iodide by all five of the DHNAs followed clean second-order kinetics which wereconsistent with a bimolecular hydride transfer.Although a chain reaction involving solely cross termination can also follow second-order kinetics, no evidence could be obtained for either chain inhibition or initiation.The reduction mechanism followed by the NADH models appears to be substrate-specific and results reached from such model studies must be evaluated with some reservation.