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Abstract
Interrupted reactions reroute established processes to new and often unanticipated end points. Of particular interest are the cases in which a known reactive intermediate takes on a new reaction pathway, either because this pathway is lower in energy or because the conventional pathway is no longer available. Through analysis of documented cases, we aim to dissect the known interrupted reactions and trace their mechanistic origins. As new chemical processes are being discovered at a seemingly ever-increasing pace, it is likely that new interrupted reactions will continue to emerge. Our hope is that the cases considered in this Review will help identify new classes of these fascinating transformations.
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Alachouzos G, Frontier AJ. Cyclization Strategies for the Concurrent Installation of Multiple Quaternary Stereogenic Centers. Isr J Chem 2021. [DOI: 10.1002/ijch.202100014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Georgios Alachouzos
- Stratingh Institute of Chemistry Rijksuniversiteit Groningen Nijenborgh 4 9747AG Groningen, The Netherlands
| | - Alison J. Frontier
- Department of Chemistry University of Rochester 414 Hutchison Hall, 100 Trustee Road Rochester New York 14627-0216 United States
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Abstract
The defining feature of the Nazarov cyclization is a 4π-conrotatory electrocyclization, resulting in the stereospecific formation of functionalized cyclopentanones. The reaction provides access to structural motifs that are found in many natural products and drug targets. Harnessing the full potential of the Nazarov cyclization broadens its utility by enabling the development of new methodologies and synthetic strategies. To achieve these goals through efficient cyclization design, it is helpful to think of the reaction as a two-stage process. The first stage involves a 4π-electrocyclization leading to the formation of an allylic cation, and the second stage corresponds to the fate of this cationic intermediate. With a complete understanding of the discrete events that characterize the overall process, one can optimize reactivity and control the selectivity of the different Stage 2 pathways.In this Account, we describe the development of methods that render the Nazarov cyclization catalytic and chemoselective, focusing specifically on advances made in our lab between 2002 and 2015. The initial discovery made in our lab involved reactions of electronically asymmetric ("polarized") substrates, which cyclize efficiently in the catalytic regime using mild Lewis acidic reagents. These cyclizations also exhibit selective eliminative behavior, increasing their synthetic utility. Research directed toward catalytic asymmetric Nazarov cyclization led to the serendipitous discovery of a 4π-cyclization coupled to a well-behaved Wagner-Meerwein rearrangement, representing an underexplored Stage 2 process. With careful choice of promoter and loading, it is possible to access either the rearrangement or the elimination pathway. Additional experimental and computational studies provided an effective model for anticipating the migratory behavior of substiutents in the rearrangements. Problem-solving efforts prompted investigation of alternative methods for generating pentadienyl cation intermediates, including oxidation of allenol ethers and addition of nucleophiles to dienyl diketones. These Nazarov cyclization variants afford cyclopentenone products with vicinal stereogenic centers and a different arrangement of substituents around the ring. A nucleophilic addition/cyclization/elimination sequence can be executed enantioselectively using catalytic amounts of a nonracemic chiral tertiary amine.In summary, the discovery and development of several new variations on the Nazarov electrocyclization are described, along with synthetic applications. This work illustrates how strongly substitution patterns can impact the efficiency of the 4π-electrocyclization (Stage 1), allowing for mild Lewis acid catalysis. Over the course of these studies, we have also identified new ways to access the critical pentadienyl cation intermediates and demonstrated strategies that exploit and control the different cationic pathways available post-electrocyclization (Stage 2 processes). These advances in Nazarov chemistry were subsequently employed in the synthesis of natural product targets such as (±)-merrilactone A, (±)-rocaglamide, and (±)-enokipodin B.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jackson J. Hernandez
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Zhang J, Jiang H, Zhu S. Cascade One-Pot Synthesis of Indanone-Fused Cyclopentanes from the Reaction of Donor-Acceptor Cyclopropanes and Enynals via
a Sequential Hydrolysis/Knoevenagel Condensation/[3+2] Cycloaddition. Adv Synth Catal 2017. [DOI: 10.1002/adsc.201700345] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jiantao Zhang
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering; South China University of Technology; Guangzhou 510640 People's Republic of China
| | - Huanfeng Jiang
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering; South China University of Technology; Guangzhou 510640 People's Republic of China
| | - Shifa Zhu
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering; South China University of Technology; Guangzhou 510640 People's Republic of China
- State Key Laboratory of Elemento-Organic Chemistry; Nankai University; Tianjin 300071 People's Republic of China
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Carmichael RA, Sophanpanichkul P, Chalifoux WA. β-Silyl-Assisted Tandem Diels–Alder/Nazarov Reaction of 1-Aryl-3-(trimethylsilyl) Ynones. Org Lett 2017; 19:2592-2595. [DOI: 10.1021/acs.orglett.7b00911] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Rachael A. Carmichael
- Department of Chemistry, University of Nevada—Reno, 1664 North Virginia Street, Reno, Nevada 89557, United States
| | - Punyanuch Sophanpanichkul
- Department of Chemistry, University of Nevada—Reno, 1664 North Virginia Street, Reno, Nevada 89557, United States
| | - Wesley A. Chalifoux
- Department of Chemistry, University of Nevada—Reno, 1664 North Virginia Street, Reno, Nevada 89557, United States
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Vinogradov MG, Turova OV, Zlotin SG. Nazarov reaction: current trends and recent advances in the synthesis of natural compounds and their analogs. Org Biomol Chem 2017; 15:8245-8269. [DOI: 10.1039/c7ob01981e] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recent applications of the Nazarov reaction to stereoselective synthesis of pharmacology-relevant cyclopentenone scaffolds are summarized.
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Affiliation(s)
- Maxim G. Vinogradov
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
| | - Olga V. Turova
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
| | - Sergei G. Zlotin
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
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Williams CW, Shenje R, France S. Catalytic, Interrupted Formal Homo-Nazarov Cyclization with (Hetero)arenes: Access to α-(Hetero)aryl Cyclohexanones. J Org Chem 2016; 81:8253-67. [DOI: 10.1021/acs.joc.6b01312] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Corey W. Williams
- School
of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Raynold Shenje
- School
of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Stefan France
- School
of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Petit
Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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Wu YK, Dunbar CR, McDonald R, Ferguson MJ, West FG. Experimental and Computational Studies on Interrupted Nazarov Reactions: Exploration of Umpolung Reactivity at the α-Carbon of Cyclopentanones. J Am Chem Soc 2014; 136:14903-11. [DOI: 10.1021/ja507638r] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Yen-Ku Wu
- X-ray Crystallography Lab, †Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada
| | - Christine R. Dunbar
- X-ray Crystallography Lab, †Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada
| | - Robert McDonald
- X-ray Crystallography Lab, †Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada
| | - Michael J. Ferguson
- X-ray Crystallography Lab, †Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada
| | - F. G. West
- X-ray Crystallography Lab, †Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada
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Scadeng O, West FG. Ready Access to Alkylidenecyclopentenones by Nazarov Cyclization/β-Elimination of 2-Hydroxyalkyl-1,4-dien-3-ones. European J Org Chem 2014. [DOI: 10.1002/ejoc.201301537] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Luo J, Zhou H, Hu J, Wang R, Tang Q. Efficient catalytic-free method to produce α-aryl cycloalkanones through highly chemoselective coupling of aryl compounds with oxyallyl cations. RSC Adv 2014. [DOI: 10.1039/c4ra01043d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Efficient catalytic-free method to produce α-aryl cycloalkanones through highly chemoselective coupling of aryl compounds with oxyallyl cations at room temperature.
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Affiliation(s)
- Juan Luo
- Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology
- College of Pharmacy
- Chongqing Medical University
- Chongqing 400016, P. R. China
- The Faculty of Laboratory Medicine
| | - Hui Zhou
- Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology
- College of Pharmacy
- Chongqing Medical University
- Chongqing 400016, P. R. China
| | - Jiwei Hu
- Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology
- College of Pharmacy
- Chongqing Medical University
- Chongqing 400016, P. R. China
| | - Rui Wang
- School of Pharmacy & Bioengineering
- Chongqing University of Technology
- Chongqing 400054, P. R. China
| | - Qiang Tang
- Chongqing Key Laboratory of Biochemistry and Molecular Pharmacology
- College of Pharmacy
- Chongqing Medical University
- Chongqing 400016, P. R. China
- The Faculty of Laboratory Medicine
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12
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Krebs M, Kalinowski M, Frey W, Claasen B, Baro A, Schobert R, Laschat S. Tricyclic challenges: synthetic approaches toward dodecahydrocyclopenta[a]indenes. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.06.070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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14
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Rueping M, Ieawsuwan W. Asymmetric Brønsted acid catalyzed carbonyl activation – organocatalytic domino electrocyclization–halogenation reaction. Chem Commun (Camb) 2011; 47:11450-2. [DOI: 10.1039/c1cc15289k] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Marx VM, LeFort FM, Burnell DJ. Trapping the Oxyallyl Cation Intermediate Derived from the Nazarov Cyclization of Allenyl Vinyl Ketones with Nitrogen Heterocycles. Adv Synth Catal 2010. [DOI: 10.1002/adsc.201000722] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Scadeng O, Ferguson MJ, West FG. Intermolecular [3 + 3]-Cycloadditions of Azides with the Nazarov Intermediate. Org Lett 2010; 13:114-7. [DOI: 10.1021/ol102651k] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Owen Scadeng
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
| | - Michael J. Ferguson
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
| | - F. G. West
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
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Rieder CJ, Winberg KJ, West FG. Olefination of α,α′-Divinyl Ketones through Catalytic Meyer−Schuster Rearrangement. J Org Chem 2010; 76:50-6. [DOI: 10.1021/jo101497f] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Curtis J. Rieder
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton AB T6G 2G2, Canada
| | - Karl J. Winberg
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton AB T6G 2G2, Canada
| | - F. G. West
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton AB T6G 2G2, Canada
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18
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Basak AK, Shimada N, Bow WF, Vicic DA, Tius MA. An organocatalytic asymmetric Nazarov cyclization. J Am Chem Soc 2010; 132:8266-7. [PMID: 20507121 DOI: 10.1021/ja103028r] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An organocatalytic asymmetric Nazarov cyclization of diketoesters that proceeds by means of a dual activation mechanism has been developed. Screening of a number of catalysts led to a new thiourea that incorporates a primary amino group. The method gives rise to cyclic products with two adjacent quaternary asymmetric carbon atoms, one of which is an all-carbon stereocenter, with complete or nearly complete diastereoselectivity and in high or very high enantiomeric excess. A brief and very convenient synthesis of the acyclic diketoester starting materials through nucleophilic addition to a ketene is also described.
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Affiliation(s)
- Ashok K Basak
- Department of Chemistry, 2545 The Mall, University of Hawaii, Honolulu, Hawaii 96822, USA
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19
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Affiliation(s)
- Yen-Ku Wu
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, Canada T6G 2G2
| | - F. G. West
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, Canada T6G 2G2
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20
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Marx VM, Burnell DJ. Nazarov cyclizations of an allenyl vinyl ketone with interception of the oxyallyl cation intermediate for the formation of carbon-carbon bonds. J Am Chem Soc 2010; 132:1685-9. [PMID: 20078119 DOI: 10.1021/ja909073r] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Treatment of an allenyl vinyl ketone with BF(3) x Et(2)O leads to a cyclic oxyallyl cation by a Nazarov reaction, and when this reaction is conducted in the presence of an acyclic diene, [4 + 3] and [3 + 2] products are obtained efficiently with high regio- and stereoselectivity. The proportion of [4 + 3] to [3 + 2] product depends on the substitution on the diene. Cyclic dienes react with the oxyallyl cation by forming only one carbon-carbon bond, but the site of bond formation can be affected by steric hindrance. Electron-rich alkenes intercept the allyl cation by forming one carbon-carbon bond, or two carbon-carbon bonds through [3 + 2] cyclization. In some instances, further treatment of the initial products with BF(3) x Et(2)O leads to equilibrated products in good yield.
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Affiliation(s)
- Vanessa M Marx
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada
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G. West F, J. Rieder C, J. Fradette R. Heteroaromatic Trapping of Tricyclic 2-Oxidocyclopentenyl Cations: A Surprisingly Efficient Example of Intermolecular Interrupted Nazarov Reaction. HETEROCYCLES 2010. [DOI: 10.3987/com-09-s(s)132] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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22
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Murugan K, Srimurugan S, Chen C. A mild, catalytic and efficient Nazarov cyclization mediated by phosphomolybdic acid. Chem Commun (Camb) 2009; 46:1127-9. [PMID: 20126735 DOI: 10.1039/b918137g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mild, selective and efficient Nazarov cyclization of divinyl ketones catalyzed by phosphomolybdic acid (PMA) is described. The process demonstrates a broad substrate scope with functional group tolerance under short reaction times. PMA supported on silica gel is more efficient than the bulk catalyst and is recycled up to three times without significant activity loss.
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Affiliation(s)
- Kaliyappan Murugan
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan, Republic of China
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23
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Marx VM, Cameron TS, Burnell DJ. Formation of halogenated cyclopent-2-enone derivatives by interrupted Nazarov cyclizations. Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.10.052] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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24
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Rieder CJ, Winberg KJ, West FG. Cyclization of Cross-Conjugated Trienes: The Vinylogous Nazarov Reaction. J Am Chem Soc 2009; 131:7504-5. [DOI: 10.1021/ja9023226] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Curtis J. Rieder
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
| | - Karl J. Winberg
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
| | - F. G. West
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, T6G 2G2, Canada
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Marx VM, Burnell DJ. Synthesis of 5-hydroxycyclopent-2-enones from allenyl vinyl ketones via an interrupted Nazarov cyclization. Org Lett 2009; 11:1229-31. [PMID: 19215105 DOI: 10.1021/ol900029d] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Treatment of an allenyl vinyl ketone with trifluoroacetic acid leads to Nazarov cyclization, and the intermediate carbocation is trapped efficiently by trifluoroacetate. Hydrolysis of the ester with methanol and basic alumina provides, in good to excellent overall yield, a 5-hydroxycyclopent-2-enone in which the alcohol is predominantly trans to a substituent at C-4.
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Affiliation(s)
- Vanessa M Marx
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3
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26
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Faza O, López C, Álvarez R, de Lera Á. Regio-, Peri-, and Torquoselectivity in Hydroxy Heptatrienyl Cation Electrocyclizations: The Iso/Homo-Nazarov Reaction. Chemistry 2009; 15:1944-56. [DOI: 10.1002/chem.200801133] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Grant TN, Rieder CJ, West FG. Interrupting the Nazarov reaction: domino and cascade processes utilizing cyclopentenyl cations. Chem Commun (Camb) 2009:5676-88. [PMID: 19774236 DOI: 10.1039/b908515g] [Citation(s) in RCA: 226] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Tina N Grant
- Department of Chemistry, Faculty of Science, E3-43 Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada T6G 2G2
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Lin CC, Teng TM, Tsai CC, Liao HY, Liu RS. Gold-Catalyzed Deoxygenative Nazarov Cyclization of 2,4-Dien-1-als for Stereoselective Synthesis of Highly Substituted Cyclopentenes. J Am Chem Soc 2008; 130:16417-23. [PMID: 18998692 DOI: 10.1021/ja806415t] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chung-Chang Lin
- Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC and Department of Science Education, National Taipei University of Education, Taipei, Taiwan, ROC
| | - Tse-Min Teng
- Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC and Department of Science Education, National Taipei University of Education, Taipei, Taiwan, ROC
| | - Chung-Chih Tsai
- Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC and Department of Science Education, National Taipei University of Education, Taipei, Taiwan, ROC
| | - Hsin-Yi Liao
- Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC and Department of Science Education, National Taipei University of Education, Taipei, Taiwan, ROC
| | - Rai-Shung Liu
- Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC and Department of Science Education, National Taipei University of Education, Taipei, Taiwan, ROC
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Banaag AR, Tius MA. Traceless chiral auxiliaries for the allene ether Nazarov cyclization. J Org Chem 2008; 73:8133-41. [PMID: 18808186 DOI: 10.1021/jo801503c] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The key stereochemical factors that determine transfer of asymmetry from the chiral auxiliary to the cyclopentenone in the allene ether version of the Nazarov reaction have been elucidated. On the basis of the new insights into the mechanism, two highly effective chiral auxiliaries were designed and prepared.
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Affiliation(s)
- April R Banaag
- University of Hawaii, Chemistry Department, Honolulu, Hawaii 96822, USA
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Abstract
A carbon-terminated interrupted Nazarov reaction is described. The trimethylsilyl enol ethers derived from propargyl vinyl ketones undergo selective proton transfer at the distal acetylenic carbon atom to provide allenyl vinyl ketones as transient intermediates. In the presence of indoles, a cascade of reactions is initiated that converts the initially formed pentadienyl cations to cyclopentenones bearing a quaternary alpha carbon atom.
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Affiliation(s)
- Ashok K Basak
- Department of Chemistry, 2545 The Mall, University of Hawaii, Honolulu, Hawaii 96822, USA
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