Syntheses and properties of 5-substituted [n](2,4)pyridinophanes, model compounds of NAD(P)
作者:Tadayoshi Oikawa、Nobuhiro Kanomata、Masaru Tada
DOI:10.1021/jo00060a018
日期:1993.4
[n](2,4)Pyridinophane derivatives 5-8 having an ester or an amide group at the 5-position were synthesized by aza-Wittig reactions between beta-substituted vinyliminophosphoranes and cyclic alpha,beta-unsaturated ketones. [beta-(Methoxycarbonyl)vinyl]- (1), [beta-(N,N-tetramethylenecarbamoyl)vinyl]-(2), [beta-(N-benzylcarbamoyl)vinyl]-(3), and (beta-carbamoylvinyl)iminophosphorane (4) were synthesized from the corresponding vinyl azides and triphenylphosphine. The heptamethylene chains of 5-(methoxycarbonyl)[7](2,4)pyridinophane (5),5-(N,N-tetramethylenecarbamoyl)[7](2,4)pyridinophane (6), and 5-(N-benzylcarbamoyl)[7](2,4)pyridinophane (7) flipped with AG(double dagger) = 11.2 (T(c) = 10.3-degrees-C), 10.8 (T(c) = 0.2-degrees-C), and 10.5 kcal/mol (T(c) = -5.2-degrees-C), respectively. At lower temperatures, the three conformations of the heptamethylene bridge were frozen. Methylpyridinium iodides 10 (n = 7, 6, and 5) derived from 6 were reduced more easily [E1/2* (half height potential) = -1.65 V (n = 7); -1.63 V (n = 6); -1.29 V vs Ag/AgCl (n = 5)] than the reference compound, 2,4-diethyl-5-(N,N-tetramethylenecarbamoyl)pyridinium ion (11) [E1/2* = -1.82 V vs Ag/AgCl]. The reduced species dimerized quickly.