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Synthesis 1993; 1993(2): 241-244
DOI: 10.1055/s-1993-25840
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Cycloaromatization of α-Oxoketene Dithioacetals with 5-Lithiomethyl-3-methylisoxazole: A New General Method for the Synthesis of Substituted and Annulated 1,2-Benzisoxazoles

Dinah Pooranchand* , J. Satyanarayana, H. Ila, H. Junjappa
  • *Department of Chemistry, North-Eastern Hill University, Shillong - 793003,Meghalaya, India
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Publication Date:
17 September 2002 (online)

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A new route to 6-substituted 4a-e and 5,6-annulated 4f-l 1,2-benzisoxazoles has been developed through regioselective 1,2-nucleophilic addition of 5-lithiomethyl-3-methylisoxazole (2) to a variety of α-oxoketene dithioacetals 1a-l and subsequent cycloaromatization of the resulting hydroxyacetals in the presence of boron trifluoride -diethyl ether complex. The corresponding 4-dethiomethylated benzisoxazoles 6a-d were also synthesized by cyclocondensation of β- methylthio-α,β-unsaturated ketones with 2 under identical conditions. The reaction was further extended for the synthesis of (6-benzisoxazolyl)-substituted ethylenes 9a-e, butadienes 9f-g and hexatriene 9h by subjecting α-cinnamoyl ketene dithioacetals 7a-e and their higher enyl analogs 7f-h to similar transformations.

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