title: A new type of donor-acceptor cyclopropane reactivity: the generation of formal 1,2- and 1,4-dipoles.
abstract: 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.
authors.affiliation: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow (Russian Federation); V. A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilov st., 119991 Moscow (Russian Federation).
authors.forename: Roman A
authors.initials: RA
authors.lastname: Novikov
authors.forename: Anna V
authors.initials: AV
authors.lastname: Tarasova
authors.forename: Victor A
authors.initials: VA
authors.lastname: Korolev
authors.forename: Vladimir P
authors.initials: VP
authors.lastname: Timofeev
authors.forename: Yury V
authors.initials: YV
authors.lastname: Tomilov
keywords: annulation; carbocycles; cyclodimerization; donor-acceptor systems; lewis acids