Divinylcyclopropanes rearrangement

Entry 3 in Scheme 6.11 illustrates the application of a c/s-divinylcyclopropane rearrangement in the prepartion of an intermediate for the synthesis of pseudoguaiane-type natural products. 

In order to use the divinylcyclopropane rearrangement for the construction of fused cycloheptanes, one of the double bonds must be incorporated in a separate, attached ring. Several practical methods have been developed to prepare the required substrates, as illustrated in Scheme 11. 

A successful formal total synthesis of ( )-quadrone (218) via a route in which a divinylcyclopropane rearrangement played a key role was achieved by employing the substrate (228 Scheme 32). This material is readily prepared from the ketone (227) and, in contrast to compounds (219) and (224), undergoes smooth Cope rearrangement to the tricyclic diene acetal (229), which is easily transformed into the keto acetal (230). A rather lengthy sequence of reactions effects conversion of (230) into the keto aldehyde (221), which, as mentioned previously, has served as an intermediate in a total synthesis of ( )-quadione (218)."... 

Muller, P., Toujas, J.-L., Bernardinelli, G. A stereospecific "2-Aza-divinylcyclopropane" rearrangement. Helv. Chim. Acta 2000, 83, 1525-1534. 

A recent synthesis of colchicine (84) featured the divinylcyclopropane rearrangement as a key step. In a model study, cyclopropane 82 in refluxing xylene gave cycloheptadiene 83 in 93% yield. 3... 

The expansion of a cyclopropane to a seven-membered ring can be efficiently achieved through a divinylcyclopropane rearrangement. Examples of this transformation have emerged from the groups of Wender, Marino (Eq. 24), Piers (Eq. 25), White (Eq. 26), Harvey (Eq. 27), Barluenga (Eq. 28), Wulff, Davies, and others. ... 

Divinylcyclopropane rearrangements have been utilized as the key step in the synthesis of a variety of natural products, including the total... 

The rate of the reaction is influenced by the energy of the starting materials, and strained compounds react at much lower temperatures than do unstrained molecules. The 1,2-divinyl derivatives of cyclopropane, cyclobutane, and cyclopentane illustrate this point. c -Divinylcyclopropane rearranges to qrcloheptadiene... 

A variety of stoichiometric complexation studies on Rh(I)-mediated VCP-CP rearrangements as well as divinylcyclopropane rearrangements have been reported. In addition, some proposed reactive intermediates have been isolated and characterized. Based on these studies, the proposed mechanism involves the formation of an rj -alkene complex 75 (Scheme... 

The conversion of (527) into (528), a hetero-analogue of the divinylcyclopropane rearrangement, and related thermal reactions have also been discussed. ... 

Twenty-one years after the discovery of the Cope rearrangement, the cyclopropanation of 1,3,5-hexatriene (38) by diazomethane in the presence of cuprous chloride resulted in the rearranged structure 40, instead of the expected cyclopropane product. In what is referred to as a divinylcyclopropane rearrangement (or cyclopropyl-Cope rearrangement), the c/5-orientation of the alkenes and the relief of cyclopropane ring strain... 

The rhodium complex (271) rearranges at 120°C to (272), with formation of the Cope product (273) being inhibited by complexation of the rhodium throughout the reaction. The analogous complex (274) from the xo-divinylcyclopropane rearranges at 65 °C to a mixture of (271) and (274) (Scheme 39), the proportions of which are solvent-dependent the transoid bis-u-allyl structure (275) is the probable intermediate. ... 

The divinylcyclopropane rearrangement has been used in a model study for the synthesis of tiglianes, daphnanes, and ingenanes [e.g. (152) - (153)], and Scott et al have outlined a new short synthesis of azulene (154) involving intramolecular carbene addition as a key stage. 

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