Arynes and donor-acceptor (D-A) cyclopropanes are two classes of strained systems having the potential for numerous applications in organic synthesis. The last two decades have witnessed a renaissance of interest in the chemistry of these species primarily because of the mild and robust methods for their generation or activation. Commonly, arynes as easily polarizable systems result in 1,2-disubstitution, whereas D-A cyclopropanes as polarized systems lead to 1,3-bisfunctionalization thereby showing striking similarities. Transformations with 1,2- and 1,3-dipoles afford cyclic structures. With arynes, emerging four-membered rings as intermediates might react further, whereas the analogous five-membered rings obtained from D-A cyclopropanes are most often the final products. However, there are a few cases where these intermediates behave surprisingly differently. This Minireview highlights the parallels in reactivity between arynes and D-A cyclopropanes thereby shedding light on the neglected similarities of these two reactive species.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201909213

Uncovering the Neglected Similarities of Arynes and Donor-Acceptor Cyclopropanes.

Nucleophilic Ring Opening of Donor–Acceptor Cyclopropanes Catalyzed by a Brønsted Acid in Hexafluoroisopropanol

Diverse Applications of Ionic Liquids: A Comprehensive Review

Indolylboron ate complexes readily generated from 2-lithioindoles and boronic esters underwent multicomponent dearomative coupling with D-A cyclopropanes and alkyl halides in the presence of Sc(OTf)3 as a catalyst. The reactions proceeded with complete diastereoselectivity and excellent stereospecificity to provide indolines containing three contiguous stereocenters. The valuable boronic ester moiety remains in the product and allows for subsequent functionalization.

Lewis Acid Catalyzed Stereoselective Dearomative Coupling of Indolylboron Ate Complexes with Donor–Acceptor Cyclopropanes and Alkyl Halides

The first example of (3+3)-annulation of two different three-membered rings is reported herein. Donor-acceptor cyclopropanes in reaction with diaziridines were found to afford perhydropyridazine derivatives in high yields and diastereoselectivity under mild Lewis acid catalysis. The disclosed reaction is applicable for the broad substrate scope and exhibits an excellent functional group tolerance.

(3+3)-Annulation of Donor-Acceptor Cyclopropanes with Diaziridines.

Lewis-acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with thioketones are described. Highly substituted tetrahydrothiophenes with two adjacent quaternary carbon atoms were obtained in a stereospecific manner under mild conditions and in high yield when using AlCl3 as Lewis acid. Moreover, an intramolecular approach was successfully implemented to gain access to sulfur-bridged [n.2.1] bicyclic ring systems. Conversion of selenoketones, the heavier analogues, under similar conditions resulted in the formation of various tetrahydroselenophenes.

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Stereospecific Reactions of Donor-Acceptor Cyclopropanes with Thioketones: Access to Highly Substituted Tetrahydrothiophenes.

Formal Insertion of Thioketenes into Donor-Acceptor Cyclopropanes by Lewis Acid Catalysis.

Reactions of 2-arylcyclopropane dicarboxylates with naphthoquinones are reported. The key feature was the use of catalytic amounts of SnCl2, 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.

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

ConspectusDonor–acceptor (D–A) cyclopropanes have gained increased momentum over the past two decades. The use of these highly strained three-membered entities paved the way to innovative and origi...

André U. Augustin

Papers

Stereospecific Reactions of Donor-Acceptor Cyclopropanes with Thioketones: Access to Highly Substituted Tetrahydrothiophenes.

Formal Insertion of Thioketenes into Donor-Acceptor Cyclopropanes by Lewis Acid Catalysis.

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

Exploiting Heavier Organochalcogen Compounds in Donor-Acceptor Cyclopropane Chemistry.

(4 + 3)-Cycloaddition of Donor-Acceptor Cyclopropanes with Thiochalcones: A Diastereoselective Access to Tetrahydrothiepines.