Search

2-Styrylcyclopropane-1,1-dicarboxylate treated with anhydrous gallium trichloride undergoes dimerization with the cyclopropane ring opening and the styryl substituent double bond involvement, leading to the formation of polysubstituted cyclic and bicyclic structures with the predominance of the former or the latter depending on the reaction conditions. Most compounds are formed with very high diastereoselectivity. Thirteen major and minor dimeric structures were isolated and reliably characterized, two of which were found to additionally include a chlorine atom. A rare for the reactions of donor-acceptor cyclopropanes example of the formation of a product with the fused cyclobutane ring was effected at–80 °C. Plausible mechanisms of observed processes were discussed.

A new process for isomerization of donor–acceptor cyclopropanes (2-arylcyclopropanedicarboxylates) by treatment with anhydrous gallium trichloride to give (2-arylalkylidene)malonates in high yields and with good selectivity has been developed. The reaction involves initial formation of a 1,2-dipolar gallium complex.

A new process for (4 + 2)-annulation of donor-acceptor cyclopropanes (DACs) with unsaturated compounds in the presence of anhydrous GaCl3 has been developed. In this process, DACs act as sources of formal 1,2- and 1,4-dipoles to give polysubstituted tetralins in high yields and with high regio- and diastereoselectivity. Alkenes with both aryl and alkyl substituents at the double bond undergo this reaction equally readily. A most likely mechanism of the reaction has been proposed. It involves preliminary generation of a key 1,2-dipolar gallium complex and its subsequent participation in annulation with an alkene.

A new process for the [4 + 2] annulation of donor–acceptor cyclopropanes with acetylenes under the effect of anhydrous GaCl3 using 1,2-zwitterion reactivity was elaborated. The reaction opens access to substituted dihydronaphthalenes, naphthalenes, and other fused carbocycles. The direction of the reaction can be efficiently controlled by temperature.

A new type of dimerization of 2-arylcyclopropane-1,1-dicarboxylates in the presence of anhydrous GaCl3 to give acyclic dimers, viz., substituted pent-2-ene-1,1,5,5-tetracarboxylates, occurs at room temperature. In this reaction, one molecule of the donor–acceptor cyclopropane manifests a non-classical reactivity and serves as a 1,2-dipole.

A new process for isomerization of donor–acceptor cyclopropanes (2-arylcyclopropanedicarboxylates) by treatment with anhydrous gallium trichloride to give (2-arylalkylidene)malonates in high yields and with good selectivity has been developed. The reaction involves initial formation of a 1,2-dipolar gallium complex.

A new type of dimerization of 2-arylcyclopropane-1,1-dicarboxylates in the presence of anhydrous GaCl3 to give acyclic dimers, viz., substituted pent-2-ene-1,1,5,5-tetracarboxylates, occurs at room temperature. In this reaction, one molecule of the donor–acceptor cyclopropane manifests a non-classical reactivity and serves as a 1,2-dipole.

A new type of donor–acceptor cyclopropane reactivity has been discovered. On treatment with anhydrous GaCl3, they react as sources of even-numbered 1,2- and 1,4-dipoles instead of the classical odd-numbered 1,3-dipoles due to migration of positive charge from the benzyl center. This type of reactivity has been demonstrated for new reactions, namely, cyclodimerizations of donor–acceptor cyclopropanes that occur as [2+2]-, [3+2]-, [4+2]-, [5+2]-, [4+3]-, and [5+4]-annulations. The [4+2]-annulation of 2-arylcyclopropane-1,1-dicarboxylates to give polysubstituted 2-aryltetralins has been developed in a preparative version that provides exceedingly high regio- and diastereoselectivity and high yields. The strategy for selective hetero-combination of donor–acceptor cyclopropanes was also been developed. The mechanisms of the discovered reactions involving the formation of a comparatively stable 1,2-ylide intermediate have been studied.