Base-catalysed rearrangement and hydrogen isotope exchange reactions of tricyclo[7.1.0.02,7]deca-2(7),3,5-triene (cyclopropindene) and related compounds

Abstract

The rates of rearrangement and hydrogen isotope exchange of the title compound, catalysed by potassium t-butoxide in dimethyl sulphoxide or by potassium t-pentoxide in t-pentyl alcohol have been measured, and compared with the exchange rates for model hydrocarbons. It is tentatively suggested that the kinetic results taken together with the low stereoselectivity in the deprotonation step may be consistent with the participation of a tricyclodecatrienyl (homoindenyl) anion intermediate possessing a small degree of homoaromatic character. Exchange in benzylcyclopropane was only slightly faster than that in isobutylbenzene, indicative of the absence of substantial stabilisation of a benzylic carbanion by an α-cyclopropyl substituent.