Reactions of Donor–Acceptor Cyclopropanes with Naphthoquinones: Redox and Lewis Acid Catalysis Working in Concert

Abstract

Reactions of 2-arylcyclopropane dicarboxylates with naphthoquinones are reported. The key feature was the use of catalytic amounts of SnCl , which acts as both an electron donor and a Lewis acid. By an in situ umpolung of naphthoquinone the formerly electrophilic species is converted into a nucleophile that is able to trigger the ring-opening of the three-membered ring with formation of a new C-C bond. Treatment of these products with base under oxidative conditions resulted-through loss of methyl formate-in cyclopentannulated products with fully conjugated π systems exhibiting intensive absorptions in the visible range.

Synthesis of Functionalized Ferrocene Derivatives from Donor−Acceptor Cyclopropanes

“…Although in general less reactive, various carbon nucleophiles are also able to participate in ring‐opening reactions of D‐A cyclopropanes. Specifically, indoles, 2‐naphthols, and some other electron‐rich (hetero)arenes demonstrated their suitability for this reactivity affording the corresponding arylation products (Scheme ) …”

Carboxylates as Nucleophiles in the Enantioselective Ring‐Opening of Formylcyclopropanes under Iminium Ion Catalysis

“…[5] This implies that important organic reactions remain elusivewhen the nucleophilic counterpart is acarboxylate anion like, for example, in the conjugate addition. [7,9] Some precedents demonstrate that Lewisa cids are efficient promoters of the ring-opening event in electrophilicc yclopropanes, [3] but the abilityo fo rganocatalysts to activate these strained substrates [10] has only been recently documented and is exclusively limited to two cases (Scheme 1). [7] It shouldb e highlighted that av ariety of heteronucleophiles have been previously used to promote ring-opening on donor-acceptor cyclopropanes, [8] typicallyr equiring powerful nucleophiless uch as amines, azides, halides, or indoles.…”

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

“…[1] Theu se of DACs as 1,3-zwitterions is known best and has been well developed. [3] Many current studies focus on DACc hemistry and the search for new variants of their chemical conversion. [3] Many current studies focus on DACc hemistry and the search for new variants of their chemical conversion.…”