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Since the pioneering work by Sarel and co-workers on the iron
carbonyl p- moted transformation of vinylcyclopropanes and related
compounds [1],a - riety of transition metal complexes have been
examined to achieve effective - tivation of the
vinylcyclopropane-cyclopentene rearrangement which usually requires
pyrolytic conditions. These reactions have been applied to natural
product synthesis in some cases and have already been reviewed in
several - cellent articles [2-4]. Contrary to the well-established
chemistry of the vinylcyclopropanes, the corresponding reactions of
alkynyl- and propadienylcyclopropanes have not, until
recently,received much attention.We present here a summary of the
recent efforts towards the development of transition metal promoted
transformation of these molecules with a brief survey of the
corresponding thermal reactions. 2 Rearrangement of
Alkynylcyclopropanols Unlike the well-known chemistry of the
vinylcyclopropane-cyclopentene - arrangement, there is no general
method for the rearrangement of alkyn- cyclopropane to cyclopentene
derivatives.One specific example is the pyrolysis of
1-ethynyl-2-methylcyclopropane to methylenecyclopentene and other
c- pounds [5]. At 530 C, 1-ethynyl-2-methylcyclopropane (1)
undergoes a [1,- hydrogen shift to give hexa-1,2,5-triene (
2),which further isomerizes to met- lenecyclopentenes 3 and 4 in 38
and 29% yield,respectively (Scheme 1).
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