216985-81-8Relevant academic research and scientific papers
Generation of cycloalkylidene carbenes via exo-type cyclization of alkynyllithiums bearing remote leaving group
Harada, Toshiro,Iwazaki, Katsuhiro,Otani, Takeshi,Oku, Akira
, p. 9007 - 9012 (1998)
The reaction of 5-hexynyl rosylate (3a) with alkynyllithium (RC≡CLi; R = Ph, TMS) gives enynes 5 and 6. The reaction proceeds through a mechanism involving a novel exo-type cyclization of 6-lithio-5-hexynyl tosylate to form cyclopentylidene carbene. Enyne 6 is produced by the addition of RC≡CLi to the carbene, whereas rearrangement of the carbene to cyclohexyne followed by carbolithiation with RC≡CLi gives enyne 5. The formation of cyclopentylidene carbene and cyclohexyne as intermediates is clearly demonstrated by trapping experiments with cyclohexene (and triethylsilane) and with 1,3- diphenylisobenzofuran, respectively. Alkynyllithiums derived from 3-butynyl and 6-heptynyl p-fluorobenzenesulfonates (19a,b) undergo a similar exo-type cyclization to give cyclopropylidene and cyclohexylidene carbenes, respectively.
