A mild and metal-free synthesis of chiral 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazines
作者:Hongyi Zhao、Shengnan Li、Shihao Cheng、Ziyun Lin、Dongfeng Zhang、Haihong Huang
DOI:10.1016/j.tet.2021.132304
日期:2021.7
Various functionalized enantiomerically pure 3-hydroxymethyl-1,4-benzoxazine derivatives, including four stereoisomers, were synthesized from chiral 2,3-epoxy-4-trityloxybutanol. The synthesis was mild and metal-free. Yields of 52%–94%, and stereoselectivities of 95% to >99% ee, were obtained. The mechanism was investigated using online Fourier-transform infrared spectroscopy. This revealed a base-promoted
从手性 2,3-epoxy-4-trityloxybutanol 合成了各种功能化的对映体纯 3-hydroxymethyl-1,4-benzoxazine 衍生物,包括四种立体异构体。合成过程温和且不含金属。获得了 52%–94% 的产率和 95% 到 >99% ee 的立体选择性。使用在线傅里叶变换红外光谱研究了该机制。这揭示了碱促进的环化作用以原位形成三环稠合的苯并恶嗪基-恶唑烷酮中间体,然后是水解过程。该方法可以很容易地按比例缩放并以一锅法进行。通过进一步衍生形成独特的三环稠合苯并恶嗪,展示了所得手性 3-羟甲基-1,4-苯并恶嗪衍生物作为结构单元的有用性。