Les β-eliminations syn et anti a partir d'une serie de 31 dihalogeno-2,3 dihydro-2,3 benzofuranes sont etudiees du point de vue cinetique dans t-BuOK-t-BuOH, en present et en l'absence de 18-crown-6, et dans EtOK-EtOH
用溴或氯将交联的共聚/苯乙烯-4-乙烯基(N-己基溴化吡啶鎓)分别转化为不溶的聚合物负载的配合物,或在与各种芳族分子的反应中研究了它们的反应性。在所有情况下,都发现试剂比试剂温和,并且将区域氧基将烷氧基和氨基取代的苯()特异性转化为4-溴代衍生物,而与之反应生成二溴代衍生物。几个苯并杂环分子被转化为取代或加成产物,即2,3-二溴-N-甲基吡咯,3-溴苯并/ b /噻吩和2,3-二溴-2,3-二氢苯并呋喃。在一系列邻烷基二取代苯衍生物,即邻二甲苯,茚满和四氢呋喃中,用各种亲电试剂建立了米尔斯-尼克森效应,与相应的溴化反应相比,溴化反应的β选择性更高。用试剂在各种烷基取代的苯中的溴化速率取决于烷基的大小以及对/邻区域选择性,在叔丁基苯的情况下为100%。
Compounds of formula I:
and pharmaceutically-acceptable salts thereof, wherein Ar and R are as defined in the specification, compositions containing such compounds and methods of using such compounds and compositions in therapy.
Regioselective electro-bromination of benzofuran (2) was achieved successfully by an adequate choice of solvents and bromide salts to afford 5-bromobenzofuran (1), 5,7-dibromobenzofuran (3), and 2,3-dibromo-2,3-dihydrobenzofuran (4), respectively. Upon electrolysis of benzofuran (2) in AcOH/H2O (100/1) containing NH4Br, substitution at the C(5)-position of benzofuran (2) proceeded smoothly to afford 5-bromobenzofuran (1). After passage of totally 4 F/mol of electricity in a similar medium, 5,7-dibromobenzofuran (3) was obtained as a sole product. On the other hand, electrolysis of benzofuran (2) in CH2Cl2/H2O (1/1) and/or AcOH/H2O (10/1) in the presence of either NaBr or NH4Br afforded 2,3-dibromo-2,3-dihydrobenzofuran (4), exclusively.
Ruzziconi, R.; Sebastiani, Giovanni V., Journal of Heterocyclic Chemistry, 1980, vol. 17, p. 1147 - 1148