Mesoionic carbenes: Reactions of 1,3-diphenyltetrazol-5-ylidene with electron-deficient alkenes, and synthesis and catalytic activities of the (tetrazol-5-ylidene)rhodium(I) complexes

✍ Scribed by Shuki Araki; Keisaku Yokoi; Ryosuke Sato; Tsunehisa Hirashita; Jun-Ichiro Setsune

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2009
• Tongue: English
• Weight: 298 KB
• Volume: 46
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.61

✦ Synopsis

Abstract

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The reactions of 1,3‐diphenyltetrazol‐5‐ylidene, a rare example of mesoionic carbenes, with electron‐deficient unsaturated compounds were studied. The carbene reacted with dimethyl 1,2,4,5‐tetrazine‐3,6‐dicarboxylate to give a 5‐tetrazoliomethylide, together with hydrazine derivatives. The reaction with tetracyanoethylene gave another methylide in low yield. On the contrary, the reactions with weaker electrophiles, such as 3,6‐diphenyl‐1,2,4,5‐tetrazine, fumalonitrile, N‐phenylmaleimide, and dimethyl acetylenedicarboxylate, did not give any coupling products, but gave phenylated products and/or Michael addition products via the degradation of the 1,3‐diphenyltetrazole ring. Novel mesoionic mono‐ and bis(carbene)‐rhodium(I) complexes were synthesized and the structures were characterized by X‐ray crystallography. Their catalytic activities for the decarbonylative addition reaction of benzoyl chloride to ethynylbenzene were investigated. J. Heterocyclic Chem., (2009).