Intermediates in the Paal-Knorr Synthesis of Pyrroles. 4-Oxoaldehydes
作者:Venkataraman Amarnath、Kalyani Amarnath、William M. Valentine、Michael A. Eng、Doyle G. Graham
DOI:10.1021/tx00044a008
日期:1995.3
The mechanism of pyrrole formation between a 4-ketoaldehyde, such as 4-oxohexanal (4), and a primary amine is examined. In organic solvents 4 readily formed the imine 6 that decomposed to pyrrole 9. In phosphate buffer (pH 7.4) the presence of deuteriums in the dideuterio (4-d2) and hexadeuterio (4-d6) analogs retarded the reaction rate by factors of 1.9 and 2.6, which are much less than the isotope
研究了4-酮醛(例如4-氧己醛(4))与伯胺之间吡咯形成的机理。在有机溶剂4中容易形成分解为吡咯9的亚胺6。在磷酸盐缓冲液(pH 7.4)中,双氘(4-d2)和六氘(4-d6)类似物中的氘将反应速率降低了1.9倍和2.6,其远小于涉及碳氢键断裂的反应所表现出的同位素效应。此外,未环酮醛的氘标记物保持完整。这些结果表明,半胱氨酸5而不是烯胺8是经历环化的中间体。由于在羰基之一上不存在甲基取代基,因此4-氧代己醛的吡咯形成速率比2,5-己二酮大2个数量级。