C-H Insertion Reactions of Nitrene Complexes

Quayle, R Rahman, S. Herbert, J. Tetrahedron Lett. 1995, 36, 8087 for another example see Quayle, R Ward, 

Arseniyadis, S. Meyer, C. Eds, Metathesis in Natural Product Synthesis, Wiley-VCH, 2010. 

Strictly speaking, the original first-generation catalyst has a slightly more complex carbene substituent. This was changed to benzylidene when the synthesis route was improved. 

Additional NHC-containing catalysts may be found in Samojlowicz, C. Bieniek, M. Grela, K. Chem. Rev. 2009, 109, 3708. 

Lippstreu, J. J. Straub, B. F. J.Am. Chem. Soc. 2005,127,7444. According to these calculations, metallacyclobutenes are not local minima. 

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