Utilization of hypervalent iodine in organic synthesis: A novel and facile two-step protocol for the synthesis of new derivatives of 1<i>H</i>-Imidazo[1,2-b]pyrazole by the cyclocondensation involving α-Tosyloxyacetophenones
作者:Ming Li、Huazheng Yang、Guilong Zhao、Lirong Wen、Wei Cao、Shusheng Zhang
DOI:10.1002/jhet.5570420205
日期:2005.3
A series of new 2-aryl-7-cyano/ethoxycarbonyl-6-methylthio-1H-imidazo[1,2-b]pyrazoles (5) have been synthesized in moderate to good yields, via a two-step cyclocondensation procedure of 5-amino-4-cyano/ethoxycarbonyl-3-methylthio-1H-pyrazole (1) and α-bromoacetophenones (3) or α-tosyloxyacetophenones (2), which were prepared by the reactions of acetophenones with [hydroxy(tosyloxy)iodo]benzene (HTIB)
一系列新的2-芳基-7-氰基/乙氧基羰基-6-甲硫基1 H-咪唑并[1,2- b ]吡唑类化合物(5)通过两步环缩合反应合成5-氨基-4-氰基/乙氧基羰基-3-甲硫基-1 H-吡唑(1)和α-溴乙酰苯(3)或α-甲苯氧基苯乙酮(2),这是通过苯乙酮与[羟基(甲苯磺酰基)的反应而制得的碘苯(HTIB)。中间体5-氨基-1-(芳酰基甲基)-4-氰基/乙氧基羰基-3-甲基硫基-1 H-吡唑类(4),已经被分离出来,作为区域选择性的证据。当使用α-甲苯磺酰苯乙酮时,反应更加环保,反应时间大大减少,合成过程更方便,更易于操作。出人意料的是,在合成4时使用碳酸钾替代碳酸钠,在1(R CN)的情况下,已分离出两种新型的环缩合产物并进行了充分表征,随后提出了一个合理的机理。