A Convenient One-Pot Synthesis of Ketene Dithioacetals
作者:Didier Villemin、Abdelkrim Ben Alloum
DOI:10.1055/s-1991-26449
日期:——
An easy synthesis of ketene dithioacetals 2 and 3 by the condensation of carbon disulfide and active methylene compounds 1 with subsequent alkylation in the presence of potassium fluoride is described.
4-diamino-5-p-chlorophenyl-6-methylthio-pyrimidine (11) was prepared from 9c as a typical example using identifical conditions described for 7. The synthesis of 5,6-fused pyrimidines (14a–f), (19) and (23a–e) was also accomplished using the cyclic ketene-S,S-acetals (13a–c) and (22a–b). The present method is found to be more convenient and efficient than reported methods for alkoxy and methylthiopyrimidines
酮醇-S,S-乙缩醛(5a–c)在醇性钠的醇盐存在下与胍和硫脲反应,得到2-氨基和2-巯基-4-烷氧基-5-芳基-6-甲基-吡啶二酰亚胺(6a–k)分别以良好的收成。α-氰基碳烯-S,S-乙缩醛(9a–d)同样产生了带有胍的5-取代的2,4-二氨基-6-烷氧基-吡啶亚胺(10a-e),总收率为50-60%。未交换的2,4-二氨基-5- p -氯苯基-6-甲硫基嘧啶(11)制备图9c为使用用于描述identifical条件的典型例子7。5,6-稠合嘧啶的合成(14a–f),(19)和(23a–e)也使用环状乙烯酮-S,S-缩醛(13a–c)和(22a–b)完成。发现本方法比报道的烷氧基和甲硫基嘧啶的方法更方便和有效。
Synthesis of Partially Reduced Imidazo[1,2-a]pyridines through an Unprecedented Base-Mediated (4+2) Cyclization
A water-mediated regioselective synthesis of 6,7-diaryl-5-oxo-2,3,5,6-tetrahydroimidazo[1,2-a]pyridine-6-carbonitriles was performed by the reaction of 2-[1-cyano-2,2-bis(methylsulfanyl)vinyl]benzonitrile with 1-aryl-2-(imidazolidin-2-ylidene)ethanones under basic conditions. This reaction involves an unprecedented (4+2) annulation.
carbonyl group in amino thiophene offers a new class of synthetic protocols for C–N cross-coupling with arylboronicacids. The bidentate N,O-chelation provides a series of advantages such as copper-catalyzed, ligand- and base-freeunder open-flask conditions. Interestingly, the combination of the C–N cross-coupling/homocoupling reactions in a domino fashion led to the bithiophene adducts featuring
Cyclocondensation of oxoketene dithioacetals with 3-aminopyrazoles: a facile highly regioselective general route to substituted and fused pyrazolo ]pyrimidines
3-amino-5-methylthio-4-phenylpyrazole (1b) withα-oxoketene dithioacetals (2a-j derived from acyclic active methylene ketones affords 5-methylthio-6,7-substituted pyrazolo[1,5-a]pyrimidines (3a-J) exclusively. The reaction was found to be equally successful for the synthesis of 7-styryl,7-(4-aryl-1,3-butadienyl) and 7-(6-aryl-1,3,5-hexatrienyl)pyrazolopyrimidines (7a-f) from the respective enoylketene dithioacetals (6a-f)