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41.
42.
Louis‐Philippe B. Beaulieu Dr. Lucie E. Zimmer Prof. Alexandre Gagnon Prof. André B. Charette 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(46):14784-14791
Herein, we report the enantio‐ and diastereoselective formation of trans‐iodo‐ and trans‐chlorocyclopropanes from α‐iodo‐ and α‐chlorozinc carbenoids by using a dioxaborolane‐derived chiral ligand. The synthetically useful iodocyclopropane building blocks were derivatized by an electrophilic trapping of the corresponding cyclopropyl lithium species or a Negishi coupling to give access to a variety of enantioenriched 1,2,3‐substituted cyclopropanes. The synthetic utility of this method was demonstrated by the formal synthesis of an HIV‐1 protease inhibitor. In addition, the related stereoselective bromocyclopropanation was also investigated. New insights about the relative electrophilicity of haloiodomethylzinc carbenoids are also presented. 相似文献
43.
Zhi-Yao Chu Na Li Dan Liang Zheng-Hui Li Yong-Sheng Zheng Ji-Kai Liu 《Tetrahedron letters》2018,59(8):715-718
The formal [3+2] cycloaddition of 1,3,5-triaryl-1,3,5-triazinanes with donor-acceptor cyclopropanes has been found to provide pyrrolidines in good to excellent yields under mild reaction conditions. Preliminary mechanistic investigation indicates that this formal [3+2] cycloaddition reaction proceeds through competing SN1 and SN2 pathways. 相似文献
44.
Lewis Acid Catalyzed Enantioselective Desymmetrization of Donor–Acceptor meso‐Diaminocyclopropanes
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Daniele Perrotta Ming‐Ming Wang Prof. Dr. Jérôme Waser 《Angewandte Chemie (International ed. in English)》2018,57(18):5120-5123
The first Lewis acid catalyzed enantioselective ring‐opening desymmetrization of a donor–acceptor meso‐diaminocyclopropane is reported. The copper(II)‐catalyzed Friedel–Crafts alkylation of indoles and one pyrrole with an unprecedented meso‐diaminocyclopropane delivered enantioenriched, diastereomerically pure urea products, which are structurally related to natural and synthetic bioactive compounds. The development of a new ligand through the investigation of an underexplored subclass of bis(oxazoline) ligands was essential for achieving high enantioselectivities. 相似文献
45.
Asymmetric [3+2] Photocycloadditions of Cyclopropanes with Alkenes or Alkynes through Visible‐Light Excitation of Catalyst‐Bound Substrates
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Xiaoqiang Huang Jiahui Lin Tianqi Shen Dr. Klaus Harms Dr. Marianna Marchini Prof. Dr. Paola Ceroni Prof. Dr. Eric Meggers 《Angewandte Chemie (International ed. in English)》2018,57(19):5454-5458
The herein reported visible‐light‐activated catalytic asymmetric [3+2] photocycloadditions between cyclopropanes and alkenes or alkynes provide access to chiral cyclopentanes and cyclopentenes, respectively, in 63–99 % yields and with excellent enantioselectivities of up to >99 % ee. The reactions are catalyzed by a single bis‐cyclometalated chiral‐at‐metal rhodium complex (2–8 mol %) which after coordination to the cyclopropane generates the visible‐light‐absorbing complex, lowers the reduction potential of the cyclopropane, and provides the asymmetric induction and overall stereocontrol. Enabled by a mild single‐electron‐transfer reduction of directly photoexcited catalyst/substrate complexes, the presented transformations expand the scope of catalytic asymmetric photocycloadditions to simple mono‐acceptor‐substituted cyclopropanes affording previously inaccessible chiral cyclopentane and cyclopentene derivatives. 相似文献
46.
Cobalt‐Catalyzed Intramolecular Reactions between a Vinylcyclopropane and an Alkyne: Switchable [5+2] Cycloaddition and Homo‐Ene Pathways
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Dr. Chunlin Wu Prof. Dr. Naohiko Yoshikai 《Angewandte Chemie (International ed. in English)》2018,57(22):6558-6562
Cobalt–diphosphine catalysts have been found to promote intramolecular reactions between a vinylcyclopropane and an alkyne to selectively afford either the [5+2] cycloaddition product or the homo‐ene reaction product under solvent control. The former product is exclusively formed in noncoordinating 1,2‐dichloroethane, whereas the latter is dominant in coordinating solvents, such as acetonitrile and dimethylacetamide. Furthermore, a highly enantioselective variant of the homo‐ene reaction afforded chiral tetrahydrofuran, pyrrolidine, and cyclopentane derivatives bearing 1,3‐diene and alkylidene substituents. 相似文献
47.
Three‐Component Gallium(III)‐Promoted Addition of Halide Anions and Acetylenes to Donor–Acceptor Cyclopropanes
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Dr. Roman A. Novikov Dr. Denis D. Borisov Dr. Anna V. Tarasova Dr. Yaroslav V. Tkachev Prof. Dr. Yury V. Tomilov 《Angewandte Chemie (International ed. in English)》2018,57(32):10293-10298
A new strategy for the three‐component addition of halide anions and acetylenes to donor–acceptor cyclopropanes (DACs) is presented. This reaction, which occurs with high E selectivity, is promoted by gallium(III) salts and based on the 1,2‐zwitterionic reactivity of DACs. It opens up a new group of processes involving DACs. The reaction occurs readily with a broad range of substrates and is tolerant of various functional groups. This methodology makes it possible to assemble highly functionalized vinyl halides, which are very convenient building blocks in organic synthesis. A possible mechanism of this reaction and its stereochemical aspects are discussed in detail. 相似文献
48.
Lingran Kong Jingjing Liu Prof. Dr. Tuoping Luo 《Angewandte Chemie (International ed. in English)》2018,57(3):760-764
A new strategy was devised for the total synthesis of highly oxidized ent‐kauranoids. A highly regio‐ and diastereoselective intermolecular Diels–Alder cycloaddition involving a diene embedded in a substituted bicyclo[4.1.0] skeleton was used to assemble all carbon centers but C17 of the target molecule at an early stage of the synthesis. Subsequent synthetic steps, including redox manipulations, SmI2‐mediated cyclization, and isomerization reactions, afforded the antitumor natural product maoecrystal P. 相似文献
49.
Brackmann F Schill H de Meijere A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6593-6600
Protected racemic and enantiomerically pure 3,4-(aminomethano)prolines rac-9 and (2S,2'R,3R,4R)-9 have been prepared applying a titanium-mediated reductive cyclopropanation as a key step. Thus, cyclopropanations of N,N-dibenzylformamide with titanacyclopropanes generated in situ from racemic or enantiomerically pure tert-butyl N-Boc-3,4-dehydroprolinates rac-8 or (S)-8 proceed diastereoselectively, and furnish the protected racemic and enantiomerically pure diamino acid 9. The latter was incorporated into three tripeptides containing glycyl, alanyl and phenylalanyl moieties. 相似文献
50.
Dechlorination of the tetrachlorocyclopentadienone dimer and perchloro-7-oxotricyclo[6.1.0.04,8]nona-2,5-diene-9-carboxylic acid N,N-diethylamide with hydride ion donors (NaBH4, LiAlH4, etc.) and electron donors (CrCl2 or Zn) were studied. The possible pathways of unusual transformations of both sterically hindered molecules are considered.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1001–1007, June, 2006. 相似文献