Methyleneketenes and Methylenecarbenes. XIV. Evidence for the Rearrangement of Cyclopent-2 enylidenecarbene to Benzene and of Cyclopentadienylidenecarbene to Benzyne

1 January 1979

journal article
Published by CSIRO Publishing in Australian Journal of Chemistry

Vol. 32 (8) , 1767-1774
https://doi.org/10.1071/ch9791767

Abstract

Flash vacuum pyrolysis of 2,2-dimethyl-5-(endo-tricyclo[5,2,1,02,6]dec-8'-ylidene)-1,3-dioxan-4,6-dione (2) at 550-800� yielded cyclopentadiene, acetone and benzene. The production of benzeneis rationalized in terms of the formation and rearrangement of cyclopent-2-enylidenecarbene (5). 2,2-Dimethyl-5-(octahydro-1',2',4'-metheno-1'H-cyclobuta[cd]pentalen-3'-ylidene)-1,3-dioxan-4,6-dione(7) yielded cyclopentadiene, acetone, biphenylene (27 %), triphenylene (12 %) and fluorenone (14%) as major products on flash vacuum pyrolysis at 550-700�. The last three compounds are considered to arise from o-benzyne, formed by rearrangement of the intermediate cyclopentadienylidenecarbene (9).

Keywords

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