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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
A Lewis Acid Catalyzed annulation to 2,1-benzisoxazoles
Kate D Otley1, Jonathan A Ellman
1Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520-8107, United States.
Abstract:
We report here a new, atom economical annulation to 2,1-benzisoxazole scaffolds via the BF3·Et2O-catalyzed reaction of glyoxylate esters and nitrosoarenes. The developed method represents a convergent route to this compound class from previously unexplored inputs and provides a range of 2,1-benzisoxazoles in moderate to high yields under convenient conditions. Along with exploration of substrate scope, initial mechanistic investigation through (18)O labeling and the synthesis of a reaction intermediate provides evidence for an unusual umpolung addition of glyoxylates to nitrosobenzenes with high O-selectivity, followed by a new type of Friedel-Crafts cyclization.
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