Intramolecular Diels−Alder Reaction of <i>N</i>-Alkyl-2-cyano-1-azadienes: A Study of the Eschenmoser Cycloreversion of Dihydrooxazines as a Route to <i>N</i>-Alkyl-2-cyano-1-azadienes
作者:Irina A. Motorina、Frank W. Fowler、David S. Grierson
DOI:10.1021/jo9614046
日期:1997.4.1
In connection with the development of the intramolecular Diels-Alder reaction (IMDA) of 1-azadienes, the 5,6-dihydro-4H-1,2-oxazine 12has been evaluated as a synthon equivalent of the 2-cyano-1-azadiene system. It was found that the dihydrooxazonium salt 27, generated in situ from the cyclic hydroxamic acid derivative 26, is converted directly to azadiene 4a via tautomerization to the corresponding
与1-氮杂二烯的分子内Diels-Alder反应(IMDA)的发展有关,已将5,6-二氢-4H-1,2-恶嗪12评估为2-氰基-1-氮杂二烯的合成子当量。系统。已经发现,由环状异羟肟酸衍生物26原位产生的二氢恶唑鎓盐27通过互变异构化成相应的烯胺和特别容易的Eschenmoser型环还原方法直接转化成氮杂二烯4a。随后发现制备合成子12的条件。在Ag(+)离子存在下,该中间体与烷基溴的N-烷基化还导致直接形成2-氰基-1-氮杂二烯产物38a-d和4a。事实证明,微波辐射氮杂二烯4a的苯溶液是实现IMDA转化为吲哚并立定5a的便捷方法。