NADH MODELS-19 CYCLOPROPANE RING AS A CHEMICAL PROBE IN THE STUDY OF THE MECHANISM OF HYDROGEN TRANSFER BY 1,4-DIHYDROPYRIDINE DERIVATIVES

Article abstract of DOI:10.1016/S0040-4020(01)91269-4

N-(Cyclopropylmethylene)phenylamines (1a-c), cyclopropyl 2-pyridyl ketones (5a-c) and ethyl cyclopropylmethylenepyruvate (14) have been subjected to reduction by 1,4-dihydropyridines <3,5-diethoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine (2) and/or 1-benzyl-1,4-dihydronicotinamide (7)> in the presence of magnesium ions, and by tin hydrides.The reactions with 1,4-dihydropyridines do not involve cleavage of the three-membered ring in the reduction step.The observed acyclic product from 2-pyridyl 2,2-dimethylcyclopropyl ketone (5b) is a consequence of ring cleavage prior to reduction of the carbonyl function.In contrast, reduction of 1a-c and 5a-c by tin hydrides leads to products in which the cyclopropane moiety has undergone ring-opening.These findings support a hydride transfer mechanism for reductions with NADH models.