Interconversion of Bicyclo[2.2.1]hept-2-yne and 5-Bicyclo[2.1.1]hexylidenecarbene

Abstract

This work provides unambiguous results for the full equilibration of cycloalkyne 2 with its isomeric ring-contracted vinylidene 3 prior to their reaction with 2,3-dihydropyran (4), as evidenced by the products formed when 2 and 3 are produced directly from their precursors having bicyclo[2.2.1]heptyl and bicyclo[2.1.1]hexyl skeletons, respectively.

Carbenes and Nitrenes

“…68 The interconversion of bicyclo[2.2.1]hept-2-yne (86) and 5-bicyclo[2.1.1]hexylidenecarbene (87) has been studied. 69 The authors claim that their results, in combination with those of an earlier study, give unambiguous support for a rapid equilibrium between the cycloalkyne and the carbene. The results presented comprise careful analysis of product mixtures.…”

“…55 Better yields and ees are achieved for tricycles (69) derived from furan than for (68) derived from more bulky pyrroles. Monocycloee propanation (with high yields and ees) is achieved on the furan ring of benzofuran, whereas double cyclopropanation of the indole is observed.…”

Stereo- and Regioselective Synthesis of Molecular Baskets

“…In support of the racemization, Gassman and co-workers discerned the formation of highly strained bicyclo[2.2.1]­heptyne (norbornyne) akin to 11 . More recently, Gilbert and co-workers demonstrated , that norbornyne acts more as a dicarbene that is in equilibrium with alkylidenecarbene 12 (Figure E). Both Komatsu’s and Hart’s research groups confirmed the transient formation of bicyclo[2.2.2]­octynes by trapping them with 1,3-diphenylisobenzofuran .…”