Reduction of arenediazonium salts by tetrakis(dimethylamino)ethylene (TDAE): efficient formation of products derived from aryl radicals.

Mohan Mahesh,Franck Lestrat,John A Murphy,Hans Peter Wessel

doi:10.3762/bjoc.5.1

Mohan Mahesh, Franck Lestrat + Show 2 more

Open Access

https://doi.org/10.3762/bjoc.5.1

Copy DOI

Abstract

Tetrakis(dimethylamino)ethylene (TDAE 1), has been exploited for the first time as a mild reagent for the reduction of arenediazonium salts to aryl radical intermediates through a single electron transfer (SET) pathway. Cyclization of the aryl radicals produced in this way led, in appropriate substrates, to syntheses of indolines and indoles. Cascade radical cyclizations of aryl radicals derived from arenediazonium salts are also reported. The relative ease of removal of the oxidized by-products of TDAE from the reaction mixture makes the methodology synthetically attractive.

Highlights

Arenediazonium salts have long proved useful as sources of aryl radicals in many reactions featuring carbon-carbon (e.g., Meerwein [1], Pschorr [2,3], Gomberg [3] reactions) and carbon-heteroatom bond (e.g., Sandmeyer [4]) formation
This paper describes the results of our investigations on reactions of TDAE as a neutral organic electron donor with arenediazonium salts
On addition of TDAE to a solution of the arenediazonium tetrafluoroborate salt 16 in acetonitrile [Table 1, entries (i) and (ii)], or, alternately, on addition of the arenediazonium salt to excess TDAE (2.5 equiv) [Table 1, entry (iii)] the reaction mixture underwent effervescence as it turned from deep red to pale orange

Summary

Introduction

Arenediazonium salts have long proved useful as sources of aryl radicals in many reactions featuring carbon-carbon (e.g., Meerwein [1], Pschorr [2,3], Gomberg [3] reactions) and carbon-heteroatom bond (e.g., Sandmeyer [4]) formation. Scheme 3: Studies on the reductive radical cyclization of arenediazonium salt 16 by TDAE.

Results

Conclusion