Arynes history

Despite the fact that the history of hetarynes is older than that of the benzynes (cf. 2), physical data on these compounds are scarce. Numerous trapping experiments furnished evidence for the formation of brradicaloid intermediates in the field of five-membered heterocycles (didehydrofurans, -thiophenes, and -pyrroles)." Direct spectroscopic data on these species, however, do not exist, which may be attributable to the increased ring strain in the five-membered o-arynes, associated with a strong tendency to undergo ring-opening reactions. 

Finally, reference must be made to benzyne and other arynes. Something of their history may be gleaned from the autobiography of R. Huisgen, whose research on... 

Tadross, P.M. and Stoltz, B.M. (2012) A comprehensive history of arynes in natural product total synthesis. Chem. Rev., 112, 3550. 

A comprehensive history of arynes in natural product total synthesis 12CRV3550. 

Despite the long history of arynes and their potential as a powerful enophile in the ene reaction (because of their low-lying LUMOs), reports on the ene reaction of arynes remain rare, especially with alkynes. Recently, an ene reaction of arynes with alkynes has been reported by Cheng and coworkers, which readily affords arylallenes (Equation 12.49) [106]. 

Some palladium-catalyzed reactions of organotins, such as carbostannylations, are not related to the Stille cross-coupling. The history of the transition-metal-cata-lyzed carbostarmylation [148] began with alkynylstannylation of alkynes catalyzed by a palladium-iminophosphine complex [149]. Thus, alkynylstannanes added to a carbon-carbon triple bond of various acetylenes, conjugated ynoates and propar-gyl amines and ethers in the presence of a catalytic amount of a palladium-iminophosphine complex [150]. The reaction also proceeded with arynes to afford ortho-substituted arylstannanes, which could further be converted into 1,2-substituted arenes via carbon-carbon bond-forming reactions [151]. 

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