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Wang C, Fan Y, Yao Y, Chen W, Cui X, Zhu G, Zhou W, Tang L. Base-Promoted Substitution Reaction: A Simple, Economical, and Efficient Method for Obtaining 3-Sulfenylated Benzo[ b
]furan Derivatives. ChemistrySelect 2018. [DOI: 10.1002/slct.201702142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Cong Wang
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
- State Key Laboratory of Functions and Applications of Medicinal Plants; Guizhou Medcial University; Guiyang 550014, Guizhou, P. R. China
- Guizhou Provincial Engineering Technology Research Center for Chemical Drug R&D; Guizhou Medical University; Guiyang 550004, Guizhou, P. R. China
| | - Yuxin Fan
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
- State Key Laboratory of Functions and Applications of Medicinal Plants; Guizhou Medcial University; Guiyang 550014, Guizhou, P. R. China
- Guizhou Provincial Engineering Technology Research Center for Chemical Drug R&D; Guizhou Medical University; Guiyang 550004, Guizhou, P. R. China
| | - Yaoyao Yao
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
| | - Wenzhang Chen
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
| | - Xing Cui
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
| | - Gaofeng Zhu
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
| | - Wei Zhou
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
| | - Lei Tang
- School of Pharmacy; Guizhou Medical University; Guiyang 550025, Guizhou, P. R. China
- State Key Laboratory of Functions and Applications of Medicinal Plants; Guizhou Medcial University; Guiyang 550014, Guizhou, P. R. China
- Guizhou Provincial Engineering Technology Research Center for Chemical Drug R&D; Guizhou Medical University; Guiyang 550004, Guizhou, P. R. China
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2
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Zhang H, Ma C, Zheng Z, Sun R, Yu X, Zhao J. Synthesis of 2-arylbenzofuran-3-carbaldehydes via an organocatalytic [3+2] annulation/oxidative aromatization reaction. Chem Commun (Camb) 2018; 54:4935-4938. [DOI: 10.1039/c8cc02474j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A novel organocatalytic [3+2] annulation/oxidative aromatization reaction of enals with 2-halophenols is developed for the synthesis of 2-arylbenzofuran-3-carbaldehydes.
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Affiliation(s)
- Huiwen Zhang
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
| | - Chunmei Ma
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
| | - Ziwei Zheng
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
| | - Rengwei Sun
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
| | - Xinhong Yu
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
| | - Jianhong Zhao
- State Key Laboratory of Bioengineering Reactors and Shanghai Key Laboratory of New Drug Design
- School of Pharmacy
- East China University of Science and Technology
- Shanghai 200237
- China
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3
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Fürstner A. Gold-Katalyse für die Heterocyclenchemie: eine repräsentative Fallstudie zu Naturstoffen der Pyron-Reihe. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201707260] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Alois Fürstner
- Max-Planck-Institut für Kohlenforschung; 45470 Mülheim/Ruhr Deutschland
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4
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Fürstner A. Gold Catalysis for Heterocyclic Chemistry: A Representative Case Study on Pyrone Natural Products. Angew Chem Int Ed Engl 2017; 57:4215-4233. [PMID: 28862364 DOI: 10.1002/anie.201707260] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Indexed: 11/06/2022]
Abstract
2-Pyrones and 4-pyrones are common structural motifs in bioactive natural products. However, traditional methods for their synthesis, which try to emulate the biosynthetic pathway of cyclization of a 1,3,5-tricarbonyl precursor, are often harsh and, therefore, not particularly suitable for applications to polyfunctionalized and/or sensitive target compounds. π-Acid catalysis, in contrast, has proved to be better for a systematic exploration of the pyrone estate. To this end, alkynes are used as stable ketone surrogates, which can be activated under exceedingly mild conditions due to the pronounced carbophilicity of [LAu]+ fragments (L=two electron donor ligand); attack of a tethered ester carbonyl group onto the transient alkyne-gold complex then forges the pyrone ring in a fully regiocontrolled manner.
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Affiliation(s)
- Alois Fürstner
- Max-Planck-Institut für Kohlenforschung, 45470, Mülheim/Ruhr, Germany
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5
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Phosphine-Mediated Sequential Annulation Reaction: Access to Functionalized Benzofurans and 4,5-Dihydrobenzofurans. Chemistry 2017; 23:7882-7886. [DOI: 10.1002/chem.201701026] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Indexed: 01/02/2023]
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6
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Preindl J, Jouvin K, Laurich D, Seidel G, Fürstner A. Gold- or Silver-Catalyzed Syntheses of Pyrones and Pyridine Derivatives: Mechanistic and Synthetic Aspects. Chemistry 2015; 22:237-47. [DOI: 10.1002/chem.201503403] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Indexed: 01/18/2023]
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7
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Debrouwer W, Heugebaert TSA, Roman BI, Stevens CV. Homogeneous Gold-Catalyzed Cyclization Reactions of Alkynes withN- andS-Nucleophiles. Adv Synth Catal 2015. [DOI: 10.1002/adsc.201500520] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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8
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Mi Y, Zhou T, Wang KP, Lee D, Xia Y. Mechanistic Understanding of the Divergent Cyclizations ofo-Alkynylbenzaldehyde Acetals and Thioacetals Catalyzed by Metal Halides. Chemistry 2015; 21:17256-68. [DOI: 10.1002/chem.201502469] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Indexed: 11/06/2022]
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9
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Han Z, Zhang L, Li Z, Fan R. Direct Assembly of 3,4-Difunctionalized Benzofurans and Polycyclic Benzofurans by Phenol Dearomatization and Palladium-Catalyzed Domino Reaction. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201404155] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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10
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Han Z, Zhang L, Li Z, Fan R. Direct assembly of 3,4-difunctionalized benzofurans and polycyclic benzofurans by phenol dearomatization and palladium-catalyzed domino reaction. Angew Chem Int Ed Engl 2014; 53:6805-9. [PMID: 24845520 DOI: 10.1002/anie.201404155] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Indexed: 11/07/2022]
Abstract
A method to directly convert 2-alkynylphenols to 3,4-difunctionalized benzofurans and polycyclic benzofurans was developed. This protocol involves a hypervalent-iodine-mediated oxidative dearomatization to break the aromaticity of 2-alkynylphenols, and a palladium-catalyzed domino reaction to install two functional groups at the C3 and the C4 positions and restore the aromaticity of benzofurans.
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Affiliation(s)
- Zhaomeng Han
- Department of Chemistry, Fudan University, 220 Handan Road, Shanghai, 200433 (China)
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11
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Adcock HV, Langer T, Davies PW. 1,2-N-migration in a gold-catalysed synthesis of functionalised indenes by the 1,1-carboalkoxylation of ynamides. Chemistry 2014; 20:7262-6. [PMID: 24828030 PMCID: PMC4204129 DOI: 10.1002/chem.201403040] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Indexed: 12/02/2022]
Abstract
Unique α-hemiaminal ether gold carbene intermediates were accessed by a gold-catalysed 1,1-carboalkoxylation strategy and evolved through a highly selective 1,2-N-migration. This skeletal rearrangement gave functionalised indenes, and isotopic labelling confirmed the rare C–N bond cleavage of the ynamide moiety. The effect of substituents on the migration has been explored, and a model is proposed to rationalise the observed selectivity.
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Affiliation(s)
- Holly V Adcock
- School of Chemistry, University of Birmingham (UK), Fax: (+44) 121-4144403
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12
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Hoffmeister L, Persich P, Fürstner A. Formal Total Synthesis of Kendomycin by Way of Alkyne Metathesis/Gold Catalysis. Chemistry 2014; 20:4396-402. [DOI: 10.1002/chem.201304580] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Indexed: 12/23/2022]
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13
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Wang CD, Hsieh YF, Liu RS. Gold-Catalyzed Carboalkoxylations of 2-Ethynylbenzyl Ethers to form 1- and 2-Indanones Chemoselectively: Effects of Ligands and Solvents. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201300988] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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14
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Cera G, Chiarucci M, Dosi F, Bandini M. Gold(I)-Catalyzed Functionalization of Benzhydryl C(sp3)H Bonds. Adv Synth Catal 2013. [DOI: 10.1002/adsc.201300525] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Ackermann M, Bucher J, Rappold M, Graf K, Rominger F, Hashmi ASK. [3,3]-Sigmatropic rearrangement step in the gold-catalyzed cyclization of allyl-(ortho-alkinylphenyl)methyl ethers. Chem Asian J 2013; 8:1786-94. [PMID: 23729410 DOI: 10.1002/asia.201300324] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Indexed: 11/09/2022]
Abstract
The gold-catalyzed conversion of allyl-(ortho-alkynylphenyl)methyl ethers was investigated, and allylated isochromenes were obtained. An optimization of the catalysis conditions with respect to different phosphane and carbene ligands on gold, different counterions, and different solvents was conducted. Subsequently, the scope and limitations of this reaction were investigated with 21 substrates. The mechanistic studies show an allylic inversion, as supported by NMR data and an X-ray crystal structure analysis, as well as an intermolecular reaction, as determined by crossover experiments. There is no competition of protodeauration even in the presence of water. All these observations differ from other related conversions and clearly indicate product formation by a [3,3]sigmatropic rearrangement in the step forming the new C-C bond.
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Affiliation(s)
- Martin Ackermann
- Organisch-Chemisches Instiut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
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16
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Brewitz L, Llaveria J, Yada A, Fürstner A. Formal Total Synthesis of the Algal Toxin (−)-Polycavernoside A. Chemistry 2013; 19:4532-7. [DOI: 10.1002/chem.201204551] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Indexed: 02/04/2023]
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17
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Tin Tetrachloride-Catalyzed Regiospecific Allylic Substitution of Quinone Monoketals: An Easy Entry to Benzofurans and Coumestans. Adv Synth Catal 2012. [DOI: 10.1002/adsc.201200344] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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18
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Sakiyama N, Noguchi K, Tanaka K. Rhodium-catalyzed intramolecular cyclization of naphthol- or phenol-linked 1,6-enynes through the cleavage and formation of sp2 C-O bonds. Angew Chem Int Ed Engl 2012; 51:5976-80. [PMID: 22532495 DOI: 10.1002/anie.201201186] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/22/2012] [Indexed: 11/06/2022]
Affiliation(s)
- Norifumi Sakiyama
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
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19
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Sakiyama N, Noguchi K, Tanaka K. Rhodium-Catalyzed Intramolecular Cyclization of Naphthol- or Phenol-Linked 1,6-Enynes Through the Cleavage and Formation of sp2CO Bonds. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201201186] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Snaddon TN, Buchgraber P, Schulthoff S, Wirtz C, Mynott R, Fürstner A. Total Synthesis of Berkelic Acid. Chemistry 2010; 16:12133-40. [DOI: 10.1002/chem.201001133] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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21
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Gruit M, Michalik D, Krüger K, Spannenberg A, Tillack A, Pews-Davtyan A, Beller M. Synthesis of pyrroloazepinones: platinum- and gold-catalyzed cyclization reactions of alkynes. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.02.091] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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22
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Sato T, Nakamura I, Terada M. Platinum-Catalyzed Multisubstituted Benzo[b]selenophene Synthesis. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900894] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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23
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Gruit M, Michalik D, Tillack A, Beller M. Platinum-Catalyzed Intramolecular Cyclizations of Alkynes: Efficient Synthesis of Pyrroloazepinone Derivatives. Angew Chem Int Ed Engl 2009; 48:7212-6. [DOI: 10.1002/anie.200902937] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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24
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Gruit M, Michalik D, Tillack A, Beller M. Platinum-Catalyzed Intramolecular Cyclizations of Alkynes: Efficient Synthesis of Pyrroloazepinone Derivatives. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200902937] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Flügge S, Anoop A, Goddard R, Thiel W, Fürstner A. Structure and Bonding in Neutral and Cationic 14-Electron Gold Alkyne π Complexes. Chemistry 2009; 15:8558-8565. [DOI: 10.1002/chem.200901062] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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26
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Nakamura I, Chan CS, Araki T, Terada M, Yamamoto Y. Stereochemical Control by an Ester Group or Olefin Ligand in Platinum-Catalyzed Carboalkoxylation of 6-(1-Alkoxyethoxy)- hex-2-ynoates. Adv Synth Catal 2009. [DOI: 10.1002/adsc.200800772] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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27
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Total Syntheses of Amphidinolides B1, B4, G1, H1 and Structure Revision of Amphidinolide H2. Chemistry 2009; 15:3983-4010. [DOI: 10.1002/chem.200802067] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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28
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Chao CM, Vitale M, Toullec P, Genêt JP, Michelet V. Asymmetric Gold-Catalyzed Hydroarylation/Cyclization Reactions. Chemistry 2009; 15:1319-23. [DOI: 10.1002/chem.200802341] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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29
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Buchgraber P, Snaddon T, Wirtz C, Mynott R, Goddard R, Fürstner A. A Synthesis-Driven Structure Revision of Berkelic Acid Methyl Ester. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200803339] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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30
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Buchgraber P, Snaddon T, Wirtz C, Mynott R, Goddard R, Fürstner A. A Synthesis-Driven Structure Revision of Berkelic Acid Methyl Ester. Angew Chem Int Ed Engl 2008; 47:8450-4. [DOI: 10.1002/anie.200803339] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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31
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Fürstner A, Schlecker A. A Gold-Catalyzed Entry into the Sesquisabinene and Sesquithujene Families of Terpenoids and Formal Total Syntheses of Cedrene and Cedrol. Chemistry 2008; 14:9181-91. [DOI: 10.1002/chem.200801382] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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32
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Takaya J, Udagawa S, Kusama H, Iwasawa N. Synthesis of N-Fused Tricyclic Indoles by a Tandem [1,2] Stevens-Type Rearrangement/1,2-Alkyl Migration of Metal-Containing Ammonium Ylides. Angew Chem Int Ed Engl 2008; 47:4906-9. [DOI: 10.1002/anie.200705517] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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33
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Takaya J, Udagawa S, Kusama H, Iwasawa N. Synthesis of N-Fused Tricyclic Indoles by a Tandem [1,2] Stevens-Type Rearrangement/1,2-Alkyl Migration of Metal-Containing Ammonium Ylides. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705517] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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34
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Nakamura I, Yamagishi U, Song D, Konta S, Yamamoto Y. Synthesis of 3- and 6-Sulfonylindoles fromortho-Alkynyl-N-sulfonylanilines by the Use of Lewis Acidic Transition-Metal Catalysts. Chem Asian J 2008; 3:285-95. [DOI: 10.1002/asia.200700278] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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35
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Fürstner A, Bonnekessel M, Blank JT, Radkowski K, Seidel G, Lacombe F, Gabor B, Mynott R. Total Synthesis of Myxovirescin A1. Chemistry 2007; 13:8762-83. [PMID: 17768720 DOI: 10.1002/chem.200700926] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A convergent total synthesis of the antibiotic macrolide myxovirescin A1 (1) is described that is largely based on reagent- and catalyst-controlled transformations. This includes a highly regioselective Negishi reaction of dibromo-alkene 48 with an alkynylzinc reagent, and a palladium catalyzed alkyl-Suzuki coupling of the resulting enyne derivative 12 with the 9-BBN-adduct derived from alkene 61. The latter was obtained via an asymmetric hydrogenation of the chlorinated beta-ketoester 49 and an anti-selective oxyallylation of the functionalized aldehyde 53 as the key steps. The preparation of the bis-borylated allyl-donor 57 used in the oxyallylation step, however, required careful optimization and led to important insights into the nature of the classical hydroborating agent "di(isopinocampheyl)borane (Ipc2BH)". It was unambiguously shown by X-ray crystallography that in the solid state this compound is dimeric, but it is prone to undergo an essentially quantitative mono-deborylation when dissolved in CH2Cl2 or benzene; its composition in ethereal solvents is even more complex as evident from 11B NMR data. Product 71 derived from 12 and 61 was elaborated into the enyne-yne derivative 75, which served as the substrate for an exquisitely selective ring closing alkyne metathesis reaction (RCAM) catalyzed by the molybdenum tris-amido complex 20 activated in situ with CH2Cl2. The resulting cyclic enyne 76 was subjected to a ruthenium catalyzed trans-hydrosilylation/proto-desilylation tandem. Although [Cp*Ru(MeCN)3]PF6 had previously been recommended as catalyst of choice for trans-hydrosilylation reactions of internal alkynes, this complex failed to afford the desired product, whereas its sterically less hindered congener [CpRu(MeCN)3]PF6 permitted the reaction to be performed in appreciable yield, but at the expense of a lower stereoselectivity. AgF-mediated proto-desilylation of the isomeric silanes 79 and 80 followed by cleavage of the remaining acetal protecting groups afforded myxovirescin A1 and its hitherto unknown 14Z-isomer 81, respectively.
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Affiliation(s)
- Alois Fürstner
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany.
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