Arynes by Loss of Nitrogen from Cyclic Systems

Arynes by Loss of Nitrogen from Cyclic Systems 

Diazonium salts with a potentially divalent o-substituent in principle could exist as either cyclic (49) or open-chain (49 ) structures. Although the former have been considered for o-diazonium carboxylates (49a), solubility and spectral properties support the zwitterionic form (41a). Other cyclic azo com- 

TABLE 3, Generation of Arynes by Loss of Nitrogen from and other Cyclic Systems 

Benzothiadiazole-1,1-dioxides (49b) lose Nj and SO2 under mild conditions to give arynes. Generally the major reaction path appears to be concerted with only minor involvement of sulfur-containing intermediates 

In contrast to 41a, benzenediazonium 2-thiocarboxylate (52) exists in the cyclic form (49c) and requires higher temperatures for aryne formation, apparently via the thiolactone intermediate 53  

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