Thermolysis of Benzannulated Enyne−Carbodiimides. Application in the Synthesis of Pyrido[1‘,2‘:1,2]pyrimido[4,5-<i>b</i>]indoles and Related Heteroaromatic Compounds
作者:Xiaoling Lu、Jeffrey L. Petersen、Kung K. Wang
DOI:10.1021/jo0204092
日期:2002.11.1
Several derivatives of the pyrido[1',2':1,2]pyrimido[4,5-b]indoles 4 and the pyrazino[1',2':1,2]pyrimido[4,5-b]indoles 14 were synthesized by treatment of the benzannulated enyne-isocyanates 8 with the iminophosphoranes 9 and 13, respectively, for the aza-Wittig reaction followed by thermolysis. The reaction presumably proceeds through an initial formation of the corresponding benzannulated enyne-carbodiimides
吡啶并[1',2':1,2,pyrimido [4,5-b]吲哚4和吡嗪并[1',2':1,2,pyrimido [4,5-b]吲哚14通过分别用亚氨基膦9和13处理苯环化的烯炔异氰酸酯8合成aza-Wittig反应,然后进行热分解,合成了苯乙炔。该反应大概是通过初始形成相应的苯并环的烯炔-碳二亚胺,例如10,然后进行正式的分子内杂Diels-Alder反应而进行的。出人意料的是,当使用亚氨基磷烷17与8缩合时,未获得预期的嘧啶并[1',6':1,2]嘧啶并[4,5-b]吲哚16。相反,分离了嘧啶并[6',1':2,3]嘧啶并[4,5-b]吲哚21异构体。想必,涉及初始[2 + 2]环加成反应以形成19,然后开环的另一种反应途径可能导致20,在分子内自由基与自由基偶联后,可能会导致21。用二溴三苯基磷烷处理脲衍生物24也就地产生了。苯甲环化的炔烃-碳二亚胺25,在热解后产生异喹啉基[2',1':1