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A direct addition of tetracyanoethylene (TCNE) at the carbene center of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) has been successfully demonstrated. The IPr-TCNE adduct, zwitterion 1, clearly differs from the typical products of [2+1]… Click to show full abstract
A direct addition of tetracyanoethylene (TCNE) at the carbene center of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) has been successfully demonstrated. The IPr-TCNE adduct, zwitterion 1, clearly differs from the typical products of [2+1] cyclization obtained from the reaction of carbenes with olefins. Experimental and theoretical studies suggest that the adduct (1) disassembles to IPr and TCNE, followed by addition of IPr to nitrile carbon of TCNE, and further isomerizes to a thermodynamically more stable singlet nitrene intermediate (3), which was captured by additional TCNE to afford another heterocycle (2). This study reveals a unique example of the reactivity between NHC and olefins.
Journal Title: European Journal of Organic Chemistry
Year Published: 2017
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