Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion
作者:Kirill V. Zavyalov、Mikail S. Novikov、Alexander F. Khlebnikov、Viktoriia V. Pakalnis
DOI:10.1016/j.tet.2014.03.101
日期:2014.5
the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.
2-羰基取代的2 H-叠氮基与2-氰基-2-重氮乙酸乙酯或2-重氮-3,3,3-三氟丙酸酯的Rh(II)催化反应可轻松获得2 H -1,3 -恶嗪和1 H-吡咯-3(2 H)-ones 。这些化合物可以使用温度作为唯一变化的参数,从相同的原料中选择性制备。两种杂环产物的共同前体2-azabuta-1,3-diene中间体在动力学控制下异构化为2 H -1,3-恶嗪,而1 H -pyrrol-3(2 H)-一个是在高温下反应的唯一产物。根据DFT计算,一个原子的恶嗪环收缩涉及开环成2-azabuta-1,3-二烯中间体,然后发生1,5-和1,2-质子性位移,导致连续形成亚氨基酰亚胺基和甲亚胺叶立德,然后进一步进行环化为吡咯衍生物。