Synthesis of 2,1-Benzisoxazoles
An efficient and facile PPh3-mediated Barbier-Grignard-type reaction provides various 3-aryl or alkyl substituted 1,2-benzisoxazoles from 2-hydroxybenzonitriles and bromides in good yields.
G. Chen, H. Liu, S. Li, Y. Tang, P. Lu, K. Xu, Y. Zhang, Org. Lett., 2017, 19, 1792-1795.
Various substituted benzisoxazoles have been prepared by a [3 + 2] cycloaddition of nitrile oxides and arynes. Both highly reactive intermediates, have been generated in situ by fluoride anion from readily prepared aryne precursors and chlorooximes. The reaction scope is quite general, affording a novel, direct route to functionalized benzisoxazoles under mild reaction conditions.
A. V. Dubrovskiy, R. C. Larock., 2010, 12, 1180-1183.
A divergent and regioselective synthesis of either 3-substituted benzisoxazoles or 2-substituted benzoxazoles from readily accessible ortho-hydroxyaryl N-H ketimines proceeds in two distinct pathways through a common N-Cl imine intermediate: (a) N-O bond formation to form benzisoxazole under anhydrous conditions and (b) NaOCl mediated Beckmann-type rearrangement to form benzoxazole, respectively.
C.-y Chen, T. Andreani, H. Li, Org. Lett., 2011, 13, 6300-6303.
An electrochemically mediated method enables the preparation of 2,1-benzisoxazoles from o-nitrophenylacetylenes. Different from the traditional electrochemical reduction of nitro to nitroso, the nitro group directly underwent a cyclization reaction with the alkyne activated by selenium cation generated by the anodic oxidation of diphenyl diselenide and finally produced the desired products.
L.-W. Wang, Y.-F. Feng, H.-M. Lin, H.-T. Tang, Y.-M. Pan, J. Org. Chem., 2021, 86, 16121-16127.