Cyclopentenes Methylenecyclopentenes

Cyclobutene/ cyclopentene/ " methylenecyclopentene/ cyclohexene/ " cycloheptene/ cyclooctene/ bicyclo[2.2.1]hepta-2-ene (norbornene)/ " " and some derivatives of norbornene " are also known to copolymerize with MA to give noncrystalline equimolar copolymers. 

Unlike the well-known chemistry of the vinylcyclopropane-cyclopentene rearrangement, there is no general method for the rearrangement of alkynyl-cyclopropane to cyclopentene derivatives. One specific example is the pyrolysis of l-ethynyl-2-methylcyclopropane to methylenecyclopentene and other compounds [5]. At 530°C, l-ethynyl-2-methylcyclopropane (1) undergoes a [1,5]-hydrogen shift to give hexa-l,2,5-triene (2), which further isomerizes to methy-lenecyclopentenes 3 and 4 in 38 and 29% yield, respectively (Scheme 1). 

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