The mechanism of two reactions leading to isomeric 2-(N,N-disubstituted amino)thiazol-5-yl ketones
作者:Katherine Challacombe、Susan E. Leach、Simon J. Plackett、G. Denis Meakins
DOI:10.1039/p19880002213
日期:——
A study has been made of the condensations between N-acyl-N′,N′-disubstituted thioureas and α-halogeno ketones [reaction (I)], and between N,N-disubstituted thioureas and 2-bromo-1,3-diketones [reaction (II)]. The mechanistic details were elucidated by using substrates with pairs of (almost) equally reactive but spectrometrically distinguishable acyl groups, e.g., CH3CO and CD3CO. In the presence of
已经研究了N-酰基-N ',N'-二取代的硫脲与α-卤代酮之间的缩合[反应(I)],以及N,N-二取代的硫脲与2-溴-1,3-之间的缩合。二酮[反应(Ⅱ)]。通过使用具有成对的(几乎)反应性相同但在光谱学上可区分的酰基,例如CH 3 CO和CD 3的底物来阐明机械细节。在添加的碱(三乙胺)存在下,两个反应均通过共同的开链1,3-二酮进行;由此,通过亲核进攻在替代的羰基上形成异构体产物,得到环状中间体,然后对其进行限速脱水。如果不添加碱,则介质变为酸性。反应(II)遵循其先前的过程,但是各阶段的相对速率相反。在反应(I)中,初始环状中间体如此迅速地脱水,以致不形成开链的1,3-二酮,并且仅产生一种异构体。