Cyclocondensation of 2-lithiomethylthiazoles and 2-lithiomethylthiazoline with α-oxoketene dithioacetals: synthesis of substituted and annelated thiazolo- and dihydrothiazolo[3,2-a]pyridinium compounds
作者:Abraham Thomas、Hiriyakkanavar Ila、Hiriyakkanavar Junjappa
DOI:10.1016/s0040-4020(01)86767-3
日期:——
The oxoketene dithioacetals 1 undergo regioselective 1,2-addition with 2-lithiomethyl-4-methylthiazole (2a) and 2-lithiomethylthiazoline (3) to afford the carbinol acetals 4 which on borontrifluoride etherate assisted cyclization yield the corresponding substituted and annelated 3-methyl-5- methylthiothiazolo[3,2-a.] pyridinium tetrafluoroborates (5a-g, 8a,b,10,12) and the dihydro derivatives (23-25)
氧杂环丁烯二硫缩醛1与2-lithiomethyl-4-甲基噻唑(2a)和2-lithiomethylthiazoline(3)进行区域选择性1,2-加成,得到甲醇缩醛4,该缩醛4在三氟化硼醚化物协助下环化生成相应的取代和退火的3-甲基-5-甲基硫代噻唑并[3,2-a。]四氟硼酸吡啶鎓(5a-g,8a,b,10,12)和二氢衍生物(23-25)的收率很高。然而,相应的2-甲基-5-苯基噻唑(16)经历了核和侧链的去质子化,并在相似的反应条件下产生了产物的混合物。