作者:Jayanta Kumar Mukhopadhyaya、Stepan Sklenák、Zvi Rappoport
DOI:10.1021/ja992059f
日期:2000.2.1
The effect of stabilizing enols of carboxamides by several two β-electron-withdrawing substituents was studied with the R1R2CHCONHPh systems. When R1R2CH2 = Meldrum's acid (MA), the solid-state structure is that of the enol R1R2CC(OH)NHPh (7). In CDCl3 solution the structure is 7, but there may be some exchange on the NMR time scale with a tautomer. B3LYP/6-31G** calculations show a significant preference
用 R1R2CHCONHPh 系统研究了几个两个 β-吸电子取代基稳定羧酰胺的烯醇的效果。当 R1R2CH2 = Meldrum 酸 (MA) 时,固态结构是烯醇 R1R2CC(OH)NHPh (7)。在CDCl3 溶液中,结构为7,但在NMR 时间尺度上可能存在一些与互变异构体的交换。B3LYP/6-31G** 计算表明,烯醇 R1R2CC(OH)NH2 (12a)(R1R2C = MA 部分)和 (MeO2C)2CC(OH)NHPh (11b) 比酰胺结构更偏爱烯醇结构。然而,固体 11 具有酰胺结构 (MeO2C)2CHCONHPh (11a)。CDCl3 中的 NMR 谱显示 >90% 的 11a,但也存在少量物质,可能是 11b。在 DMSO 中没有观察到这种物质。类似的二甲酮取代的苯胺 10 以固态和溶液形式作为环羰基的烯醇存在。计算表明,HC(CO2Me)3 的能量低于其互变