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Journal ArticleDOI: 10.1021/ACS.ACCOUNTS.1C00023

Exploiting Heavier Organochalcogen Compounds in Donor-Acceptor Cyclopropane Chemistry.

04 Mar 2021-Accounts of Chemical Research (American Chemical Society)-Vol. 54, Iss: 6, pp 1528-1541
Abstract: 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...

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14 results found

Journal ArticleDOI: 10.1021/JACS.1C07088
Abstract: The importance of intramolecular constraints in cyclic transition-state geometries is especially pronounced in n-endo-tet cyclizations, where the usual backside approach of a nucleophile to the breaking bond is impossible for the rings containing less than eight atoms. Herein, we expand the limits of endo-tet cyclizations and show that donor-acceptor cyclopropanes can provide a seven-membered ring via a genuine 6-endo-tet process. Substrates containing a N-alkyl-N-arylcarbamoyl moiety as an acceptor group undergo Lewis acid-induced cyclization to form tetrahydrobenz[b]azepin-2-ones in high yields. The reaction proceeds with the inversion of the configuration at the electrophilic carbon. In this process, a formally six-membered transition state yields a seven-membered ring as the pre-existing cycle is merged into the forming ring. The stereochemistry of the products can be controlled by the reaction time and by the nature of Lewis acid, opening access to both diastereomers by tuning of the reaction conditions.

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Topics: Lewis acids and bases (56%), Ring (chemistry) (55%), Nucleophile (54%) ... read more

4 Citations

Journal ArticleDOI: 10.1021/ACS.ORGLETT.1C01890
Simon Kolb1, Nils L. Ahlburg1, Daniel B. Werz1Institutions (1)
07 Jul 2021-Organic Letters
Abstract: We describe a general electrochemical method to functionalize donor-acceptor (D-A) cyclopropanes and -butanes with arenes utilizing Friedel-Crafts-type reactivity. The catalyst-free strategy relies on the direct anodic oxidation of the strained carbocycles, which leads after C(sp3)-C(sp3) cleavage to radical cations that act as electrophiles for the arylation reaction. Broad reaction scopes in regard to cyclopropanes, cyclobutanes, and aromatic reaction partners are presented. Additionally, a plausible electrolysis mechanism is proposed.

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Topics: Electrophile (52%), Friedel–Crafts reaction (52%)

1 Citations

Open accessJournal ArticleDOI: 10.1039/D1OB01922H
Dongxin Zhang1, Qihang Cheng1, Lvjia Chen1, Huiqing Deng1  +2 moreInstitutions (1)
Abstract: [3 + 2] annulations of oxindole based spirocyclic donor–acceptor cyclopropanes and ynamides catalyzed by copper triflate have been developed for the synthesis of biologically important spirocyclopenteneoxindoles. These reactions tolerated a wide scope of substrates and provided the desired products in good to high yields (up to 90%) with up to >40 : 1 diastereoselectivities under mild conditions.

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78 results found

Journal ArticleDOI: 10.1002/ANIE.201309886
26 May 2014-Angewandte Chemie
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.

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Topics: Ring strain (52%)

659 Citations

Journal ArticleDOI: 10.1039/C4OB02117G
Abstract: This review summarizes research directed towards the formation of carbocyclic adducts from donor–acceptor cyclopropanes. The focus of the review is on annulation and cycloaddition reactions (both inter- and intramolecularly) mediated by Lewis or protic acid, bases, or thermal conditions. Rearrangements resulting in carbocycles and those reactions mediated by transition metal catalysis have been excluded.

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Topics: Annulation (52%), Cycloaddition (50%)

307 Citations

Journal ArticleDOI: 10.1021/JACS.5B04429
Hao Xu1, Jiang-Lin Hu1, Lijia Wang1, Saihu Liao1  +1 moreInstitutions (1)
Abstract: An efficient [4 + 3] cycloaddition reaction of D–A cyclopropanes with dienes has been successfully developed. The reaction proceeds well with various dienolsilyl ethers in the presence of Lewis acid, delivering a variety of cycloheptenes and [n,5,0]carbobicycles with excellent stereoselectivity. The asymmetric version of this reaction is also realized using a newly designed chiral Cy-TOX ligand, providing a new approach to access optically active cycloheptenes and [n,5,0]carbobicycles. Mechanisic study reveals that the reaction involves a stepwise pathway, which undergoes an unusual ring opening of five-membered [3 + 2] intermediate and sequential intramolecular cyclization to afford the thermodynamically stable [4 + 3] annulation product.

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Topics: Annulation (60%), Cycloaddition (60%), Lewis acids and bases (52%)

134 Citations

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