Cyclocondensation of oxoketene dithioacetals with 3-aminopyrazoles: a facile highly regioselective general route to substituted and fused pyrazolo ]pyrimidines
作者:Abraham Thomas、Manjaree Chakraborty、Hiriyakkanavar Ila、Hiriyakkanavar Junjappa
DOI:10.1016/s0040-4020(01)85438-7
日期:1990.1
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)
3-氨基吡唑(1a)和3-氨基-5-甲硫基-4-苯基吡唑(1b)与α-氧杂环丁烯二硫缩醛(2a-j衍生自无环活性亚甲基酮的环缩合反应生成5-甲硫基-6,7-取代的吡唑并[1] ,5-a]嘧啶(3a-J),发现该反应对于合成7-苯乙烯基,7-(4-芳基-1,3-丁二烯基)和7-(6-芳基-相应的烯基烯酮二硫缩醛(6a-f)中的1,3,5-六三烯基)吡唑并嘧啶(7a-f)。同样,1a和1b与环烯基和苯并环烯酮二硫缩醛的反应也可选择性地在区域内提供有角度稠合的5-甲基硫代吡唑并嘧啶然而,来自环戊酮的氧杂环丁烯二硫缩醛分别以几乎相等的量产生角和线性稠合的区域异构体10和11。用阮内镍对一些5-甲基硫代吡唑并嘧啶进行脱硫甲基化,以高收率得到5-未取代的衍生物。