A New Golden Age for Donor–Acceptor Cyclopropanes

Abstract

The effective use of ring strain has been applied to considerable advantage for the construction of complex systems. The focus here is directed towards cyclopropanes as building blocks for organic synthesis. Although thermodynamics should take the side of synthetic chemists, only a specific substitution pattern at the cyclopropane ring allows for particularly mild, efficient, and selective transformations. The required decrease in the activation barrier is achieved by the combined effects of vicinal electron-donating and electron-accepting moieties. This Review highlights the appropriate tools for successfully employing donor-acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.

An Efficient Method for the Synthesis of 2′,3′-Nonsubstituted Cycloalkane-1,3-dione-2-spirocyclopropanes Using (2-Bromoethyl)diphenylsulfonium Trifluoromethanesulfonate

“…1,2) Ring-opening cyclization of doubly activated cyclopropanes has emerged as a powerful method for the synthesis of a variety of carbo-and heterocyclic compounds. [3][4][5][6] Recently, we demonstrated the formation of indole skeletons by employing the ring-opening cyclization of the doubly activated spirocyclopropanes, 2′-arylcyclohexane-1,3-dione-2-spirocyclopropanes 1, with primary amines 7) (Chart 1). The reaction proceeded regioselectively at room temperature (r.t.) to give 2-aryltetrahydroindol-4-ones 2, one of which was easily converted to the 4-hydroxyindole derivative 3.…”

(±)-Methyl 1,1a,2,7b-Tetrahydro-2-oxocyclopropa[c] Chromene-1a-carboxylate

“…And this scaffold serves as key intermediates for many useful organic syntheses because of its unique combination of reactivity and structural properties [1][2][3].Consequently, a considerable attention has been directed towards the stereoselective construction of these three-membered carbocyclic ring systems over the past few decades [4]. Recently, among diverse cyclopropane compounds, donor-acceptor (D-A) cyclopropane has attracted many organic chemists due to its special character containing donor and acceptor substituents at vicinal positions [5,6].…”

[3+2] Redox‐Neutral Cycloaddition of Nitrocyclopropanes with Styrenes by Visible‐Light Photocatalysis

“…[2] The [3+ +2] cycloaddition reactiono fn itrogen-based cyclopropanes with olefins is ap articularly attractive strategy for their synthesis. [3] Recently,[ 3 + + 2] cycloadditionso fn itrogen-based "donor-acceptor" cyclopropanes with silyl enolates or indoles have been successfully realized for the synthesis of nitrogenbased cyclopentanes (Scheme 1a). [4] The [3+ +2] cycloaddition of arylamino cyclopropanes with olefins was reported by Zheng [5] by using an aryl group as the protecting group and [Ru(bpz) 3 (PF 6 ) 2 ]( bpz = bipyrazyl) as ao ne-electron oxidant upon irradiation with visible light (Scheme 1b).…”