Nitrogen bridgehead compounds. Part 29. Tautomerism and Z–E isomerism of ethyl 9-aminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates and their homologues
作者:Gábor Tóth、Áron Szöllősy、Benjamin Podányi、István Hermecz、Ágnes Horváth、Zoltán Mészáros、István Bitter
DOI:10.1039/p29830001409
日期:——
1 H and 13C n.m.r. studies have proved that ethyl 9-dimethylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates (2)–(5) and the corresponding pyrrolo homologue (6) exist in the form of E-isomers whereas the azepino[1,2-a]pyrimidine derivative (7) appears as an equilibrium mixture of Z-and E-isomers. On the basis of 15N chemical shifts an analogous tautomeric structure
1 H和13 C nmr研究证明,乙基9-二甲基氨基亚甲基-4-氧代6,7,8,9-四氢-4 H-吡啶基[1,2- a ]嘧啶-3-羧酸盐(2)–( 5)和相应的吡咯并同源物(6)以E-异构体的形式存在,而azepino [1,2- a ]嘧啶衍生物(7)以Z-和E-异构体的平衡混合物的形式出现。基于15 N化学位移,已经为9-二甲基氨基亚甲基衍生物(2)-(7)和乙基9-芳基氨基亚甲基-4-氧代-6,7,8,9-四氢-4建立了类似的互变异构结构H-吡啶酮[1,2- a] pyrimidine-3-羧酸盐(8)–(12)也是如此。Z - E异构现象和分子远端部分的结构变化也敏感地影响了15 N移位。化合物(2)–(12)的质子化发生在N(1)原子上,形成1,6,7,8-四氢结构。