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Dimirjian CA, Castiñeira Reis M, Balmond EI, Turman NC, Rodriguez EP, Di Maso MJ, Fettinger JC, Tantillo DJ, Shaw JT. Synthesis of Spirobicyclic Pyrazoles by Intramolecular Dipolar Cycloadditions/[1s, 5s] Sigmatropic Rearrangements. Org Lett 2019; 21:7209-7212. [PMID: 31486651 DOI: 10.1021/acs.orglett.9b02124] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation of fused pyrazoles via intramolecular 1,3-dipolar cycloadditions of diazo intermediates with pendant alkynes is described. A subsequent thermal [1s, 5s] sigmatropic shift of these pyrazole systems resulted in a ring contraction, forming spirocyclic pyrazoles. The limitations of this rearrangement were explored by changing the substituents on the nonmigrating aromatic ring and by using substrates lacking an aromatic linkage to the propargyl group.
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Affiliation(s)
- Christine A Dimirjian
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Marta Castiñeira Reis
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Edward I Balmond
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Nolan C Turman
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Elys P Rodriguez
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Michael J Di Maso
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - James C Fettinger
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Dean J Tantillo
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Jared T Shaw
- Department of Chemistry , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
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Braun M, Hohmann A, Rahematpura J, Bühne C, Grimme S. Synthesis and Determination of the Absolute Configuration of Fugomycin and Desoxyfugomycin: CD Spectroscopy and Fungicidal Activity of Butenolides. Chemistry 2004; 10:4584-93. [PMID: 15378637 DOI: 10.1002/chem.200400132] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The dibromoalkenes (S)-3 and (R)- and (S)-4 are intermediates in the syntheses of the naturally occurring fungicidal butenolides fugomycin (1) and desoxyfugomycin (2), respectively. The stereoselective bromine-lithium exchange that leads to the carbenoid 12 and the vinyllithium reagent 17 a on the one hand, and palladium-catalyzed coupling reactions of the dibromoalkene 3 and the bromolactone 22 on the other are key steps en route to the butenolides 1 and 2. The chiral building blocks (S)-3, (R)-4, and (S)-4 are readily available from (R)-isopropylideneglyceraldehyde 5, isobutyl (R)-lactate 6 a, and ethyl (S)-lactate 6 b, respectively. The synthetic procedure adopted here permits the absolute configuration of the natural products fugomycin (1) and desoxyfugomycin (2) to be assigned by comparison of their chiroptical properties with those of the synthetic products. The CD spectra of the bromolactone 22, calculated by two different density functional methods (TDDFT, DFT/MRCI), are found to be in good agreement with the measured spectra. On the basis of these calculations, the two CD bands observed could be assigned to n-pi* and pi-pi* transitions, respectively. Fugomycin (1) and the synthetic butenolide 20 displayed high fungicidal activity against botrytis in greenhouse experiments, whereas the saturated lactone 21 was practically inactive.
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Affiliation(s)
- Manfred Braun
- Institut für Organische Chemie und Makromolekulare Chemie, Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
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Affiliation(s)
- Brian Halton
- School of Chemical & Physical Sciences, Victoria University of Wellington, P. O. Box 600, Wellington, New Zealand.
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Heinz Karsch H, Hanika G, Huber B, Riede J, Müller G. Monomere Phosphinoborane: Synthese eines Tetraalkylphosphinoborans und seine Umwandlung unter Retro- und Re-hydroborierung zu einem dimeren Phosphinoboran sowie Synthese eines Triphosphinoborans. J Organomet Chem 1989. [DOI: 10.1016/0022-328x(89)85393-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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