Accessing Dihydro-1,2-oxazine via Cloke–Wilson-Type Annulation of Cyclopropyl Carbonyls: Application toward the Diastereoselective Synthesis of Pyrrolo[1,2-<i>b</i>][1,2]oxazine
作者:Pankaj Kumar、Rakesh Kumar、Prabal Banerjee
DOI:10.1021/acs.joc.0c00531
日期:2020.5.15
A convenient additive-free synthesis of dihydro-4H-1,2-oxazines via a Cloke-Wilson-type ring expansion of the aryl-substituted cyclopropane carbaldehydes with the hydroxylamine salt is introduced. Comparatively less active cyclopropyl ketones also follow a similar protocol if supplemented by catalytic p-toluene sulfonic acid monohydrate. The transformation is performed in an open-to-air flask as it
通过芳基取代的环丙烷甲醛与羟胺盐的Cloke-Wilson型扩环,方便地合成了二氢-4H-1,2-恶嗪。如果由催化对甲苯磺酸一水合物补充,则活性相对较低的环丙基酮也遵循类似的方案。由于它对空气/水分的敏感性可以忽略不计,因此在露天烧瓶中进行转化。当二氢-4H-1,2-恶嗪与环丙烷二酯进行环加成反应时,可以很容易地配制出有价值的六氢-2H-吡咯并[1,2-b] [1,2]恶嗪衍生物。这种两步策略的级联一锅法变体可提供最终产品相当的总产量。