Synthesis of 2-Difluoroethylated 2<i>H</i>-1,3-Benzoxazines via Proton-Mediated Ring Opening/Interrupted Ritter Reaction of 1,1-Difluorocyclopropanes
作者:Kohei Fuchibe、Taro Matsuo、Junji Ichikawa
DOI:10.1021/acs.orglett.3c01277
日期:2023.6.16
2-(1,1-Difluoroethyl)-2H-1,3-benzoxazines were synthesized by (i) the regioselective ring opening of 1,1-difluorocyclopropanes bearing an aryloxy group and (ii) the Ritter reaction followed by a Friedel–Crafts-type ring closure. When 2-aryloxy-1,1-difluorocyclopropanes were treated with triflic acid, the C–C bond distal to the CF2 moiety was cleaved regioselectively via protonation to generate the
2-(1,1-二氟乙基)-2 H -1,3-苯并恶嗪通过 (i) 带有芳氧基的 1,1-二氟环丙烷的区域选择性开环和 (ii) Ritter 反应,然后是 Friedel–工艺型环扣。当用三氟甲磺酸处理 2-芳氧基-1,1-二氟环丙烷时,CF 2部分远端的 C-C 键通过质子化作用区域选择性地裂解,生成相应的氧碳正离子。这些中间体很容易受到腈的亲核攻击,然后进行碳阳离子环化,得到 2-二氟乙基化苯并恶嗪。