Transition metal complexes of diazenes XLI: cobalt catalyzed addition of internal alkynes to 1,2-diaryldiazenes: formation of 2,3-dihydrocinnolines, mono- and distilbenylazobenzenes
作者:U. Dürr、F.W. Heinemann、H. Kisch
DOI:10.1016/s0022-328x(98)00404-5
日期:1998.5
selectively this ring is ortho-metalated in the case of cobalt while only the unsubstituted or both rings are attacked in rhodium catalysis. This difference enables a two-step regioselective cobalt catalyzed synthesis of the corresponding N-anilinoindole via isolation of 2-stilbenyl-3,5-difluoroazobenzene and subsequent acid catalyzed rearrangement to the indole derivative. Results obtained with 4-methoxytolan
偶氮苯与内部炔烃之间的CoH 3(PPh 3)3催化的加成反应生成2-苯乙烯基偶氮苯和异构体2,3-二氢辛啉,它们是铑在同一底物上铑催化形成N-苯胺基吲哚的中间体。通过单晶X射线结构分析解析了六个加合物的结构。在这两个反应中,将炔烃插入M–H键和1,2-二氮苯的正金属化是催化循环的关键步骤。当如3,5-二氯-和3,5-二氟偶氮苯中只有二氮烯的一个苯环被取代时,该环选择性地是邻位的-在钴的情况下被金属化,而在铑催化中只有未取代的环或两个环都受到攻击。该差异使得能够通过分离2-苯乙烯基-3,5-二氟偶氮苯并随后酸催化重排成吲哚衍生物而对相应的N-苯胺吲哚进行两步区域选择性钴催化的合成。用4-甲氧基甲苯磺酸获得的结果表明,插入Co-H键中会产生区域异构体,其比例取决于三键极化的符号。据推测,插入时最初会提供一个顺式-烯基配体,该配体会进行有效的顺式-反式异构化,除非十氟甲苯磺酸是炔烃。在这种情况