Unusual formation of 7-vinylcycloheptatriene derivatives in the catalytic cyclopropanation of cyclooctatetraene with diazocarbonyl compounds in the presence of rhodium catalysts

The reaction of cyclooctatetraene with methyl diazoacetate or diazaacetone in the presence of rhodium binuclear complexes gives, besides 9-substituted bicyclo[6.1.0]nona-2,4,6-trienes (mixture of anti- and syn-isomers, total yields 60-75%), isomeric beta-(cyclohepta-2,4,6-trien-1-yl)acrylates or 4-( cyclohepta-2,4,6-trien-1-yl)but-3-en-2-one in 20-34% yields. In the case of methyl diazoacetate, a mixture of E- and Z-isomers in a ratio of similar t o 3.5 : 1 was obtained, while diazoacetone gave only E-isomer.