Tetrahedron Letters

Richter cyclization and co-cyclization reactions of triazene-masked diazonium ions

A Goeminne, PJ Scammells, SM Devine, BL Flynn

Index: Goeminne, Annelies; Scammells, Peter J.; Devine, Shane M.; Flynn, Bernard L. Tetrahedron Letters, 2010 , vol. 51, # 52 p. 6882 - 6885

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Citation Number: 25

Abstract

The conventional Richter cyclization involves diazotization of 2-alkynylanilines with HX (aq)(X= Br or Cl) and NaNO2, followed by spontaneous ring closure to give a mixture of 4- halocinnoline and 4-cinnolinone products. The different products result from competing attack of X− and H2O, respectively, upon an intermediate 2-alkynylphenyl diazonium ion during the cyclization step. In order to improve the chemoselectivity of this reaction, we ...