51
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Leng HJ, Peng F, Zingales S, Huang W, Wang B, Zhao Q, Zhou R, He G, Peng C, Han B. Core-Scaffold-Inspired Asymmetric Synthesis of Polysubstituted Chiral Hexahydropyridazines that Potently Inhibit Breast Cancer Cell Proliferation by Inducing Apoptosis. Chemistry 2015; 21:18100-8. [PMID: 26498568 DOI: 10.1002/chem.201503063] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 02/05/2023]
Abstract
The highly enantioselective preparation of pharmacologically interesting hexahydropyridazine derivatives based on a multicomponent cascade reaction is described. This one-pot approach utilizes an organocatalytic Michael reaction followed by intermolecular α-amination and intramolecular hemiaminalization to yield a chiral pyridazine backbone with contiguous stereogenic centers and multiple functional groups in good yield and with high stereoselectivity. Compounds synthesized by this method potently inhibited proliferation of MCF-7 breast cancer cells. Mechanistic studies suggest that compound 5 c exerts these anticancer effects by inducing apoptosis through extracellular signal related kinase (ERK)- and poly(adenosine diphosphate ribose) polymerase (PARP)-regulated pathways, as well as mitochondrial pathways.
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Affiliation(s)
- Hai-Jun Leng
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China)
| | - Fu Peng
- School of Chinese Medicine, University of Hong Kong, Hong Kong (P.R. China)
| | - Sarah Zingales
- Department of Chemistry, Armstrong State University, Savannah, GA (USA)
| | - Wei Huang
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China)
| | - Biao Wang
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China)
| | - Qian Zhao
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China)
| | - Rui Zhou
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu 610041 (P.R. China)
| | - Gu He
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu 610041 (P.R. China).
| | - Cheng Peng
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China).
| | - Bo Han
- State Key Laboratory Breeding Base of Systematic Research, Development and Utilization of Chinese Medicine Resources, School of Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137 (P.R. China).
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52
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Lee DJ, Ko D, Yoo EJ. Rhodium(II)-Catalyzed Cycloaddition Reactions of Non-classical 1,5-Dipoles for the Formation of Eight-Membered Heterocycles. Angew Chem Int Ed Engl 2015; 54:13715-8. [DOI: 10.1002/anie.201506764] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Indexed: 11/11/2022]
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53
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Lee DJ, Ko D, Yoo EJ. Rhodium(II)-Catalyzed Cycloaddition Reactions of Non-classical 1,5-Dipoles for the Formation of Eight-Membered Heterocycles. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201506764] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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54
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Eliasen AM, Christy M, Claussen KR, Besandre R, Thedford RP, Siegel D. Dearomatization Reactions Using Phthaloyl Peroxide. Org Lett 2015; 17:4420-3. [DOI: 10.1021/acs.orglett.5b02008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anders M. Eliasen
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, MC0756, La Jolla, California 92093, United States
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
| | - Mitchell Christy
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
| | - Karin R. Claussen
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
| | - Ronald Besandre
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
| | - Randal P. Thedford
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
| | - Dionicio Siegel
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, MC0756, La Jolla, California 92093, United States
- Department
of Chemistry, University of Texas at Austin, Norman Hackerman Building, Austin, Texas 78701, United States
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55
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Guo C, Fleige M, Janssen-Müller D, Daniliuc CG, Glorius F. Switchable selectivity in an NHC-catalysed dearomatizing annulation reaction. Nat Chem 2015; 7:842-7. [DOI: 10.1038/nchem.2337] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 07/14/2015] [Indexed: 02/07/2023]
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56
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Abstract
Azomethine imines are considered 1,3-dipoles of the aza-allyl type which are transient intermediates and should be generated in situ but can also be stable and isolable compounds. They react with electron-rich and electron-poor olefins as well as with acetylenic compounds and allenoates mainly by a [3 + 2] cycloaddition but they can also take part in [3 + 3], [4 + 3], [3 + 2 + 2] and [5 + 3] with different dipolarophiles. These 1,3-dipolar cycloadditions (1,3-DC) can be performed not only under thermal or microwave conditions but also using metallo- and organocatalytic systems. In recent years enantiocatalyzed 1,3-dipolar cycloadditions have been extensively considered and applied to the synthesis of a great variety of dinitrogenated heterocycles with biological activity. Acyclic azomethine imines derived from mono and disubstituted hydrazones could be generated by prototropy under heating or by using Lewis or Brønsted acids to give, after [3 + 2] cycloadditions, pyrazolidines and pyrazolines. Cyclic azomethine imines, incorporating a C-N bond in a ring, such as isoquinolinium imides are the most widely used dipoles in normal and inverse-electron demand 1,3-DC allowing the synthesis of tetrahydro-, dihydro- and unsaturated pyrazolo[1,5-a]isoquinolines in racemic and enantioenriched forms with interesting biological activity. Pyridinium and quinolinium imides give the corresponding pyrazolopyridines and indazolo[3,2-a]isoquinolines, respectively. In the case of cyclic azomethine imines with an N-N bond incorporated into a ring, N-alkylidene-3-oxo-pyrazolidinium ylides are the most popular stable and isolated dipoles able to form dinitrogen-fused saturated and unsaturated pyrazolopyrazolones as racemic or enantiomerically enriched compounds present in many pharmaceuticals, agrochemicals and other useful chemicals.
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Affiliation(s)
- Carmen Nájera
- Departamento de Química Orgánica, Facultad de Ciencias, and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
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57
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Cheng QQ, Qian Y, Zavalij PY, Doyle MP. Lewis Acid/Rhodium-Catalyzed Formal [3 + 3]-Cycloaddition of Enoldiazoacetates with Donor–Acceptor Cyclopropanes. Org Lett 2015; 17:3568-71. [DOI: 10.1021/acs.orglett.5b01674] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Qing-Qing Cheng
- Department
of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Yu Qian
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Peter Y. Zavalij
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Michael P. Doyle
- Department
of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, United States
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58
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Zhang L, Liu H, Qiao G, Hou Z, Liu Y, Xiao Y, Guo H. Phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines. J Am Chem Soc 2015; 137:4316-9. [PMID: 25799312 DOI: 10.1021/jacs.5b01138] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The first phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines is described. Using a spirocyclic chiral phosphine as the catalyst, a novel class of pharmaceutically interesting 4,6,7,11b-tetrahydro-1H-pyridazino[6,1-a]iso-quinoline derivatives were obtained in high yields with good to excellent diastereoselectivities and extremely excellent enantioselectivities (98->99% ee).
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Affiliation(s)
- Lei Zhang
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Honglei Liu
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Guanyu Qiao
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Zhanfeng Hou
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Yang Liu
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Yumei Xiao
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
| | - Hongchao Guo
- Department of Applied Chemistry, China Agricultural University, Beijing 100193, P. R. China
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59
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The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2013. Coord Chem Rev 2015. [DOI: 10.1016/j.ccr.2014.09.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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60
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Huang S, Kötzner L, De CK, List B. Catalytic asymmetric dearomatizing redox cross coupling of ketones with aryl hydrazines giving 1,4-diketones. J Am Chem Soc 2015; 137:3446-9. [PMID: 25715060 DOI: 10.1021/ja511200j] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
An asymmetric Brønsted acid catalyzed dearomatizing redox cross coupling reaction has been realized, in which aryl hydrazines react with ketones to deliver 1,4-diketones, bearing an all-carbon quarternary stereocenter in high enantiopurity.
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Affiliation(s)
- Shenlin Huang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Lisa Kötzner
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Chandra Kanta De
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Benjamin List
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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61
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Zhang Y, Wu S, Wang S, Fang K, Dong G, Liu N, Miao Z, Yao J, Li J, Zhang W, Sheng C, Wang W. Divergent Cascade Construction of Skeletally Diverse “Privileged” Pyrazole-Derived Molecular Architectures. European J Org Chem 2015. [DOI: 10.1002/ejoc.201403673] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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62
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He X, Xiao Y, Du W, Chen Y. Enantioselective Formal [3+3] Cycloadditions of Ketones and Cyclic 1‐Azadienes by Cascade Enamine–Enamine Catalysis. Chemistry 2015; 21:3443-8. [PMID: 25573519 DOI: 10.1002/chem.201404550] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 12/09/2014] [Indexed: 11/10/2022]
Affiliation(s)
- Xiao‐Long He
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, Sichuan University, Chengdu 610041 (China)
| | - You‐Cai Xiao
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, Sichuan University, Chengdu 610041 (China)
| | - Wei Du
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, Sichuan University, Chengdu 610041 (China)
| | - Ying‐Chun Chen
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, Sichuan University, Chengdu 610041 (China)
- College of Pharmacy, Third Military Medical University, Chongqing 400038 (China)
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63
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64
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Xu X, Deng Y, Yim DN, Zavalij PY, Doyle MP. Enantioselective cis-β-lactam synthesis by intramolecular C-H functionalization from enoldiazoacetamides and derivative donor-acceptor cyclopropenes. Chem Sci 2015; 6:2196-2201. [PMID: 26029355 PMCID: PMC4444070 DOI: 10.1039/c4sc03991b] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
β-Lactam derivatives are produced through donor–acceptor cyclopropene intermediates in high yield with exclusive cis-diastereoselectivity, and high enantiocontrol.
β-Lactam derivatives are produced through intermediate donor–acceptor cyclopropene intermediates in high yield, exclusive cis-diastereoselectivity, and high enantiocontrol in a chiral dirhodium carboxylate catalyzed intramolecular C–H functionalization reaction of enoldiazoacetamides.
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Affiliation(s)
- Xinfang Xu
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China. Tel: +86 0512 65883612
| | - Yongming Deng
- Department of Chemistry and Biochemistry University of Maryland, College Park, Maryland 20742
| | - David N Yim
- Department of Chemistry and Biochemistry University of Maryland, College Park, Maryland 20742
| | - Peter Y Zavalij
- Department of Chemistry and Biochemistry University of Maryland, College Park, Maryland 20742
| | - Michael P Doyle
- Department of Chemistry and Biochemistry University of Maryland, College Park, Maryland 20742
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65
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Li Z, Yu H, Feng Y, Hou Z, Zhang L, Yang W, Wu Y, Xiao Y, Guo H. Phosphine-catalyzed [4 + 3] cycloaddition reaction of aromatic azomethine imines with allenoates. RSC Adv 2015. [DOI: 10.1039/c5ra04374c] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
An efficient phosphine-catalyzed [4 + 3] cycloaddition of aromatic azomethine imines with allenoates has been developed, providing dinitrogen-fused heterocyclic compounds in moderate to excellent yields.
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Affiliation(s)
- Zhen Li
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Hao Yu
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Yalin Feng
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Zhanfeng Hou
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Lei Zhang
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Wenjun Yang
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Yang Wu
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Yumei Xiao
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
| | - Hongchao Guo
- Department of Applied Chemistry
- China Agricultural University
- Beijing 100193
- China
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66
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Yuan C, Liu H, Gao Z, Zhou L, Feng Y, Xiao Y, Guo H. Cu(I)-Catalyzed Highly Enantioselective [3 + 3] Cycloaddition between Two Different 1,3-Dipoles, Phthalazinium Dicyanomethanides and Iminoester-Derived Azomethine Ylides. Org Lett 2014; 17:26-9. [DOI: 10.1021/ol503169d] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Chunhao Yuan
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Honglei Liu
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Zhenzhen Gao
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Leijie Zhou
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Yalin Feng
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Yumei Xiao
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
| | - Hongchao Guo
- Department
of Applied Chemistry, China Agricultural University, Beijing 100193, China
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67
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N-Imide Ylide-Based Reactions: CH Functionalization, Nucleophilic Addition and Cycloaddition. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201400631] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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68
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69
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Lee DJ, Han HS, Shin J, Yoo EJ. Multicomponent [5 + 2] cycloaddition reaction for the synthesis of 1,4-diazepines: isolation and reactivity of azomethine ylides. J Am Chem Soc 2014; 136:11606-9. [PMID: 25101524 DOI: 10.1021/ja5061609] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Air-stable azomethine ylides with an unusual pattern of charge distribution were efficiently prepared via the rhodium-catalyzed reaction between pyridines and 1-sulfonyl-1,2,3-triazoles. This reaction allowed for the first example of the catalytic multicomponent [5 + 2] cycloaddition reactions, thus resulting in the formation of biologically active 1,4-diazepine compounds.
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Affiliation(s)
- Dong Jin Lee
- Department of Chemistry, Kangwon National University , 1 Kangwondaehak-gil, Chuncheon 200-701, Korea
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70
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Karad SN, Liu RS. Gold-Catalyzed 1,2-Oxoarylations of Nitriles with Pyridine-Derived Oxides. Angew Chem Int Ed Engl 2014; 53:5444-8. [DOI: 10.1002/anie.201403015] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Indexed: 01/09/2023]
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71
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Karad SN, Liu RS. Gold-Catalyzed 1,2-Oxoarylations of Nitriles with Pyridine-Derived Oxides. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201403015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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72
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Xu X, Doyle MP. The [3 + 3]-cycloaddition alternative for heterocycle syntheses: catalytically generated metalloenolcarbenes as dipolar adducts. Acc Chem Res 2014; 47:1396-405. [PMID: 24650430 PMCID: PMC3993878 DOI: 10.1021/ar5000055] [Citation(s) in RCA: 274] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Indexed: 12/12/2022]
Abstract
The combination of two or more unsaturated structural units to form cyclic organic compounds is commonly referred to as cycloaddition, and the combination of two unsaturated structural units that forms a six-membered ring is formally either a [5 + 1]-, [4 + 2]-, [2 + 2 + 2]-, or [3 + 3]-cycloaddition. Occurring as concerted or stepwise processes, cycloaddition reactions are among the most useful synthetic constructions in organic chemistry. Of these transformations, the concerted [4 + 2]-cycloaddition, the Diels-Alder reaction, is by far the best known and most widely applied. However, although symmetry disallowed as a concerted process and lacking certifiable examples until recently, stepwise [3 + 3]-cycloadditions offer advantages for the synthesis of a substantial variety of heterocyclic compounds, and they are receiving considerable attention. In this Account, we present the development of stepwise [3 + 3]-cycloaddition reactions from virtual invisibility in the 1990s to a rapidly growing synthetic methodology today, involving organocatalysis or transition metal catalysis. With origins in organometallic or vinyliminium ion chemistry, this area has blossomed into a viable synthetic transformation for the construction of six-membered heterocyclic compounds containing one or more heteroatoms. The development of [3 + 3]-cycloaddition transformations has been achieved through identification of suitable and compatible reactive dipolar adducts and stable dipoles. The reactive dipolar species is an energetic dipolar intermediate that is optimally formed catalytically in the reaction. The stepwise process occurs with the reactive dipolar adduct reacting as an electrophile or as a nucleophile to form the first covalent bond, and this association provides entropic assistance for the construction of the second covalent bond and the overall formal [3 + 3]-cycloaddition. Organocatalysis is well developed for both inter- and intramolecular synthetic transformations, but the potential of transition metal catalysis for [3 + 3]-cycloaddition has only recently emerged. The key to the rapid development of the transition metal-based methodology has been recognition that certain catalytically generated vinylcarbenes are effective dipolar adducts for reactions with stable dipolar compounds, including aryl and vinyl ylides. In particular, metallo-enolcarbenes that are generated catalytically from conveniently prepared stable enoldiazoacetates or from donor-acceptor cyclopropenes are highly effective dipolar adducts for [3 + 3]-cycloaddition. The electron-donating oxygen of the silyl ether enhances electrophilic ring closure to the metal-bound carbon of the initial adduct from vinylogous addition, and this enhancement inhibits the alternative [3 + 2]-cycloaddition across the carbon-carbon double bond of the vinylcarbene. Catalytically generated metallo-enolcarbenes react under mild conditions with a broad spectrum of compatible stable dipoles, including nitrones, azomethine imines, ylides, and certain covalent precursors of stable dipoles, to form [3 + 3]-cycloaddition products having the β-ketoester functionality (in dihydrooxazines, tetrahydropyridazines, pyrazolidinone and pyraxole derivatives, dihydroquinolines, and quinolizidines, for example) in high yield. Two ways to access these metallo-enolcarbenes, either by dinitrogen extrusion from enoldiazoacetate esters or by rearrangement of donor-acceptor cyclopropenes, enhance the versatility of the process. The [3 + 3]-cycloaddition methodology is a complementary strategy to [4 + 2]-cycloaddition for the synthesis of heterocyclic compounds having six-membered rings. High levels of enantioselectivity are obtained with the use of chiral ligands on transition metal catalysts that include those on dirhodium(II) and silver(I).
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Affiliation(s)
- Xinfang Xu
- Department of Chemistry and
Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Michael P. Doyle
- Department of Chemistry and
Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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