Generation of Cycloalkylidene Carbenes via Exo-Type Cyclization of Alkynyllithiums Bearing Remote Leaving Group

T Harada, K Iwazaki, T Otani, A Oku

Index: Harada, Toshiro; Iwazaki, Katsuhiro; Otani, Takeshi; Oku, Akira Journal of Organic Chemistry, 1998 ,  vol. 63,  # 24  p. 9007 - 9012

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Citation Number: 32

Abstract

The reaction of 5-hexynyl tosylate (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 ...