A Multistep Flow Process for the Synthesis of Highly Functionalized Benzoxazoles
摘要:
An efficient and scalable transformation of 3-halo-N-acyl anilines to the corresponding benzoxazoles within a continuous flow reactor is reported. This transformation proceeds via base-mediated deprotonation, ortho-lithiation, and intramolecular cyclization to provide unstable lithiated benzoxazole moieties. The subsequent in-line electrophilic quench results in the formation of substituted benzoxazoles in high yield and quality. Continuous flow technology allowed for accurate temperature control and immediate in-line quench while minimizing the hold-up time for the unstable lithiated intermediates thereby minimizing associated byproduct formation.
Approaches to the Synthesis of 2,3-Dihaloanilines. Useful Precursors of 4-Functionalized-1<i>H</i>-indoles
作者:Verónica Guilarte、M. Pilar Castroviejo、Patricia García-García、Manuel A. Fernández-Rodríguez、Roberto Sanz
DOI:10.1021/jo200406f
日期:2011.5.6
2,3-Dihaloanilines have been proved as useful starting materials for synthesizing 4-halo-1H-indoles. Subsequent or in situ functionalization of the prepared haloindoles allows the access to a wide variety of 2,4- or 2,3,4-regioselectively functionalized indoles in good overall yields. As no efficient synthetic routes to 2,3-dihaloanilines have been described in the literature, different approaches