Bicyclo hexadiene reduction

The thermal reaction, at room temperature, of A -bicyclo[2A0]hexene (277) gave, besides polymeric material, a dimer now identified as 2,5-dimethylenetricyclo-[4,2,2,0 ]decane (278). Reaction of (277) with irons, frans-dimethyl-2,5-hexadiene gave the olefin (279) and reduction of both (278) and (279) gave cis-2,5-dimethyltri-cyclo[4,2,2,0 ]decane. The reactive double bond in (277) differs from that usually associated with thermal olefin dimerizations. In most cases, such reactivity has been associated with double bonds which are torsionally strained. In (277) the torsion angle about the double bond must be zero and the reactivity must be associated with angular deformation at the olefinic carbons. Addition of ketene to (277) gave 3-methyl-6-methylenecyclohex-2-ene-l-one. In both reaction with ketene and dimerization, [2,2,2]propellanes would appear to be reasonable intermediates. 

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