Vinylcyclopropane- cyclopentene

An illustrative example for the generation of cyclopentenes from vinylcyclopropanes is the formation of bicyclo[3.3.0]oct-l-ene 10 from 1,1-dicyclopropylethene 9 by two consecutive vinylcyclopropane cyclopentene rearrangements. ... 

Temperatures in parentheses refer to thermal vinylcyclopropane -> cyclopentene rearrangement. 

The extrapolation of the vinylcyclopropane-cyclopentene rearrangement to a vinyl-cyclobutaiie-cyclohexene synthesis begins to create new insights into the synthesis of six membered ring natural products. The eudesmane sesquiterpene (—)-P-selinene, 217 illustrates such a strategy as summarized in Scheme 14 80). A suitable cyclohexene... 

Vinylcyclopropanation cyclopentenes. The lithium dienolate of 1 adds to a,p-enones to form an a-keto vinylcyclopropane, which on pyrolysis (550°) provides a bicyclic keto acrylate (equation I).1... 

Since the pioneering work by Sarel and co-workers on the iron carbonyl promoted transformation of vinylcyclopropanes and related compounds [1], a variety of transition metal complexes have been examined to achieve effective activation 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 excellent articles [2-4]. 

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). 

C. Doubleday, Mechanism of the Vinylcyclopropane-Cyclopentene Rearrangement Studied by Quasiclassical Direct D3mamics, J. Phys. Chem. A 2001, 105, 6333. 

Vinylcyclopropane-Cyclopentene, Bergman, Di-jr-methane, and Related Diradical Rearrangements... 

Vinylcyclopropane - cyclopentene.2 This one-electron oxidant permits rapid rearrangement of some vinylcyclopropanes to cyclopentenes in CH3CN at ambient temperatures. 

Because of the discovery of a growing number of naturally occurring substances of biological importance that contain the five-membered ring moiety 178), the synthesis of cyclopentanoid compounds is a subject of present interest. Indeed, among the various approaches recently investigated, the thermal vinylcyclopropane-cyclopentene rearrangement of readily available 1-siloxy-l-vinylcyclopropanes (vide supra, Sect. 4.1.5) constitutes an efficient three-carbon annelation process 179). 

Doubleday, C. Nendel, M. Houk, K. N. Thweatt, D. Page, M. Direct dynamics quasiclassical trajectory study of the stereochemistry of the vinylcyclopropane-cyclopentene rearrangement, J. Am. Chem. Soc. 1999,121,4720-4721. 

The conversation of free and Cr(CO)s-complexed 2-vinylphosphirane into 2,5-dihydro-17/-phosphole via 1,3-sigmatropic shifts was studied with DFT and compared with the corresponding vinylcyclopropane-cyclopentene rearrangement (Equation 2) <2002JA13903>. 2-Vinylphosphirane has smaller barriers as in the case of vinylcyclo-propane and the complexed species has still smaller one. The rearrangement of syn- and /F2-vinylphosphirane is a... 

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