One-pot synthesis of 2,1-benzisoxazoles (anthranils) by a stannous chloride-mediated tandem reduction-heterocyclization of 2-nitroacylbenzenes under neutral conditions |
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Authors: | Jay ChauhanSteven Fletcher |
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Institution: | a Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 N. Pine Street, Baltimore, MD 21201, USA b University of Maryland Marlene and Stewart Greenebaum Cancer Center, 22 S. Greene Street, Baltimore, MD 21201, USA |
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Abstract: | Classically, 2,1-benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-benzisoxazoles would be welcomed. We demonstrate that SnCl2·2H2O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction-heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid-labile protecting groups, including Boc carbamate, tert-butyl ether, and tert-butyl ester, proved orthogonal to these reaction conditions. |
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Keywords: | 2 1-Benzisoxazole/anthranil Reduction Heterocyclization Stannous chloride 2-Nitroacylbenzene |
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