1 H和13 C NMR光谱已用于检测和表征碱性溶液中连二亚硫酸根阴离子对3-氨基甲酰基或3-氰基取代的吡啶鎓盐的攻击而形成的加合物。在所有研究的情况下,仅发现由连二亚硫酸根氧阴离子攻击吡啶鎓环的碳4形成的1,4-二氢吡啶-4-亚磺酸盐。这种绝对的区域选择性似乎表明吡啶鎓阳离子与连二亚硫酸盐之间通过形成刚性取向的离子对形成了非常特殊的相互作用,从而决定了进攻的位置。在弱碱性溶液中,加合物根据两种机理S N i和S N i'分解:S Ni路径在所有研究的情况下均有效,并保留了1,4-二氢结构,产生相应的1,4-二氢吡啶,而S N i'路径涉及2,3或5,6双键的移位,从而产生1,2 -或1,6-二氢吡啶。除了1,4-二氢异构体之外,1,2-或1,6-二氢吡啶的形成还取决于它们各自的热力学稳定性。
Thermodynamic characteristics of NADH/NAD<sup>+</sup> analogues in acetonitrile: 2-methyl, 4-methyl and 2,4-dimethyl 1-benzyl-dihydronicotinamides and the corresponding pyridinium species
作者:Agnès Anne、Jacques Moiroux
DOI:10.1139/v95-068
日期:1995.4.1
Procedures were elaborated for the syntheses of the title compounds. The thermodynamic changes brought about by each methyl substitution were then determined quantitatively. In acetonitrile, the respective one-electron oxidation and one-electron reduction potentials of the NADH and NAD+ analogues were obtained by means of direct and indirect (using ferrocene mediators) cyclic voltammetry. The redox
In order to better understand the regioselective hydride transfer of metal hydrido complexes to NAD(P)(+) model compounds, reactions of [Ru(tpy)(bpy)H](+) (Ru-H: tpy = 2,2':6 '',2 ''-terpyridine, bpy = 2,2'-bipyridine) with various substituent NAD(P)(+) model compounds were investigated in detail. All of the NAD(P)(+) model compounds accepted hydride from Ru-H, yielding 1:1 adducts, where the dihydro form(s) of the model compounds coordinated with the carbamoyl group to the Ru(II) center of [Ru(tpy)(bpy)](2+), with very different reaction rates. Some reactions produced the adduct with only the 1,4-dihydro structure, whereas others produced a mixture of two adducts, with a 1,4- or 1,2-dihydro structure. In particular, temperature-dependent adduct formation kinetics studies provided important information on the transition state(s) of the hydride transfer reactions and factors for determining the regioselectivity. Most adducts were cleaved to the corresponding free dihydro product(s) with the same distribution of the regioisomers to the adduct(s).