Synthesis and radical ring opening behaviour of 1,1-difluoro-2-heptyl-2-vinylcyclopropane and some of its isomers

The syntheses and characterisations of 1,1-difluoro-2-heptyl-2-vinylcyclopropane and some of its isomers are described together with attempts to effect free radical ring opening polymerisation. We have recently shown that the parent monomer, 1,1-difluoro-2-vinylcyclopropane, undergoes predominantly 1,4-addition ring opening in contrast to the more usual 1,5-ring opening of other substituted vinylcyclopropanes and we find that the same anomalous behaviour occurs in this work confirming the influence of fluorine on the course of cyclopropane ring opening proposed by Dolbier. The presence of an alkyl chain modifies the ratios of 1,4- to 1,5-ring opening compared to that found in the unsubstituted parent monomer. In addition an the unexpected behaviour of different alkyl substituted buta-1,3-dienes towards difluorocarbene addition is described.