Department of Chemistry , Indian Institute of Technology , Kanpur 208016 , India.
J Org Chem. 2018 Aug 3;83(15):7907-7918. doi: 10.1021/acs.joc.8b00788. Epub 2018 Jun 18.
Novel 3,4-dihydro-1,4-benzoxazine derivatives have been synthesized by an efficient and simple method in excellent enantio- and diastereospecificity (ee > 99%, de > 99%). The reaction proceeds via Lewis acid-catalyzed S2-type ring opening of activated aziridines with 2-halophenols followed by Cu(I)-catalyzed intramolecular C-N cyclization in a stepwise fashion under one-pot conditions to furnish the 3,4-dihydro-1,4-benzoxazine derivatives in excellent yields (up to 95%). The strategy offers a short and efficient synthesis to ( S)-3-methyl-1,4-benzoxazine ( S)-3v, a late stage intermediate in the synthesis of levofloxacin.
新型 3,4-二氢-1,4-苯并恶嗪衍生物通过高效、简单的方法合成，具有优异的对映选择性和非对映选择性（ee>99%，de>99%）。该反应通过路易斯酸催化的活化氮丙啶与 2-卤代苯酚的 S2 型开环反应，然后在一锅条件下通过 Cu(I)催化的分子内 C-N 环化反应，以分步方式进行，以优异的收率（高达 95%）得到 3,4-二氢-1,4-苯并恶嗪衍生物。该策略提供了一种简短、高效的合成方法，用于（S）-3-甲基-1,4-苯并恶嗪（S）-3v 的合成，（S）-3v 是左氧氟沙星合成的后期中间体。
