Three‐Component Gallium(III)‐Promoted Addition of Halide Anions and Acetylenes to Donor–Acceptor Cyclopropanes

Abstract

Anew strategy for the three-component addition of halide anions and acetylenes to donor-acceptor cyclopropanes (DACs) is presented. This reaction, whicho ccurs with high E selectivity,i sp romoted by gallium(III) salts and based on the 1,2-zwitterionic reactivity of DACs.Itopens up anew group of processes involving DACs.T he reaction occurs readily with abroad range of substrates and is tolerant of various functional groups.This methodology makes it possible to assemble highly functionalizedv inyl halides,w hicha re very convenient building blocks in organic synthesis.Apossible mechanism of this reaction and its stereochemical aspects are discussed in detail.

Donor‐Acceptor Cyclopropanes in the Synthesis of Carbocycles

“…[2k,6] These substrates have been also found to react as synthetic equivalents of alkylidene malonates. [7] Based on these advances, total syntheses of diverse natural products from D-A cyclopropanes have been developed. [2c,m,n,s,8] With all these achievements in mind, Werz and co-authors have characterized this period as "A new golden age for donor-acceptor cyclopropanes".…”

“…Moreover, D‐A cyclopropanes have been successfully introduced into dynamic kinetic asymmetric transformations (DYKAT) . These substrates have been also found to react as synthetic equivalents of alkylidene malonates . Based on these advances, total syntheses of diverse natural products from D‐A cyclopropanes have been developed .…”

Three-Component GaHal3-Promoted Reactions of Substituted Methylidenemalonates and Donor–Acceptor Cyclopropanes with Propargyl Halides: Cascade Diastereoselective Construction of Five-Membered Lactones

“…The use of gallium halides makes it possible to completely modify their wellknown reactivity that they show in the presence of other Lewis acids. 9,10 This is achieved by in situ generation of specific 1,2zwitterionic gallium complexes (3, 4) (Scheme 1). To date, the formation of two types of complexes has been shown, viz., ionic complexes [Ga(L) 3 ] 3+ [GaX 4 − ] 3 (3) with a ligand/gallium ratio of 3:4 10 and covalent complexes 4 with a 1:1 ratio.…”

“…Their chemistry has been studied most thoroughly for cyclopropanedicarboxylates 2 as starting compounds for generation of complexes. 9 For example, the reactions of their dimerization 9a and various pathways of reactions with alkenes, 9d acetylenes, 9a,e aldehydes, 9b pyrazolines, 9e etc. have been studied.…”