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Villarreal-Parra M, Di Gresia GE, Labadie GR, Vallejos MM. Understanding the Fate of the Banert Cascade of Propargylic Azides: Sigmatropic versus Prototropic Pathway. J Org Chem 2023. [PMID: 37418758 DOI: 10.1021/acs.joc.3c00371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
The Banert cascade is an efficient synthetic strategy for obtaining 4,5-disubstituted 1,2,3-triazoles. The reaction can proceed via a sigmatropic or prototropic mechanism depending on the substrate and the conditions. In this work, the mechanisms of both pathways from propargylic azides with different electronic features were investigated using density functional theory, quantum theory of atoms in molecules, and natural bond orbital approaches. The calculated energy barriers were consistent with the experimental data. Three patterns of electron density distribution on the transition structures were observed, which reflected the behaviors of the reactants in the Banert cascade. The stronger conjugative effects were associated with lower/higher free activation energies of sigmatropic/prototropic reactions, respectively. A clear relationship between the accumulation of the charge at the C3 atom of propargylic azides with the energy barriers for prototropic reactions was found. Thus, the obtained results would allow the prediction of the reaction's course by evaluating reactants.
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Affiliation(s)
- Miguel Villarreal-Parra
- Instituto de Química Rosario, UNR, CONICET, Suipacha 531, S2002LRK Rosario, Argentina
- Departamento de Química Orgánica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
| | - Gabriel E Di Gresia
- Instituto de Química Rosario, UNR, CONICET, Suipacha 531, S2002LRK Rosario, Argentina
- Departamento de Química Orgánica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
| | - Guillermo R Labadie
- Instituto de Química Rosario, UNR, CONICET, Suipacha 531, S2002LRK Rosario, Argentina
- Departamento de Química Orgánica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
| | - Margarita M Vallejos
- Instituto de Química Básica y Aplicada del NEA (IQUIBA-NEA, UNNE-CONICET), Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Av. Libertad 5460, 3400 Corrientes, Argentina
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2
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Carlson AS, Topczewski JJ. Allylic azides: synthesis, reactivity, and the Winstein rearrangement. Org Biomol Chem 2019; 17:4406-4429. [PMID: 30969292 PMCID: PMC6530792 DOI: 10.1039/c8ob03178a] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Organic azides are useful synthetic intermediates, which demonstrate broad reactivity. Unlike most organic azides, allylic azides can spontaneously rearrange to form a mixture of isomers. This rearrangement has been named the Winstein rearrangement. Using allylic azides can result in low yields and azide racemization in some synthetic contexts due to the Winstein rearrangement. Effort has been made to understand the mechanism of the Winstein rearrangement and to take advantage of this process. Several guiding principles can be used to identify which azides will produce a mixture of isomers and which will resist rearrangement. Selective reaction conditions can be used to differentiate the azide isomers in a dynamic manner. This review covers all aspects of allylic azides including their synthesis, their reactivity, the mechanism of the Winstein rearrangement, and reactions that can selectively elaborate an azide isomer. This review covers the literature from Winstein's initial report to early 2019.
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Affiliation(s)
- Angela S Carlson
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
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3
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Shen MH, Liang XC, Li C, Wu H, Qu HY, Wang FM, Xu HD. Rhodium promoted intramolecular [4 + 2] cycloaddition of 2-azidodiene with alkyne: A transition metal catalysis approach to challenging fused bicyclic vinyl azide. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.03.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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4
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Ott AA, Packard MH, Ortuño MA, Johnson A, Suding VP, Cramer CJ, Topczewski JJ. Evidence for a Sigmatropic and an Ionic Pathway in the Winstein Rearrangement. J Org Chem 2018; 83:8214-8224. [PMID: 29870252 DOI: 10.1021/acs.joc.8b00961] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The spontaneous rearrangement of allylic azides is thought to be a sigmatropic reaction. Presented herein is a detailed investigation into the rearrangement of several allylic azides. A combination of experiments including equilibrium studies, kinetic analysis, density functional theory calculations, and selective 15N-isotopic labeling are included. We conclude that the Winstein rearrangement occurs by the assumed sigmatropic pathway under most conditions. However, racemization was observed for some cyclic allylic azides. A kinetic analysis of this process is provided, which supports a previously undescribed ionic pathway.
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Affiliation(s)
- Amy A Ott
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Mary H Packard
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Manuel A Ortuño
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Alayna Johnson
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Victoria P Suding
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Christopher J Cramer
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
| | - Joseph J Topczewski
- Department of Chemistry , University of Minnesota Twin Cities , Minneapolis , Minnesota 55455 , United States
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5
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Kang HY, Kang YK. Allylic Azide Rearrangements Investigated by Density Functional Theory Calculations. B KOREAN CHEM SOC 2017. [DOI: 10.1002/bkcs.11318] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Han-Young Kang
- Department of Chemistry; Chungbuk National University; Cheongju Chungbuk, 28644 Korea
| | - Young Kee Kang
- Department of Chemistry; Chungbuk National University; Cheongju Chungbuk, 28644 Korea
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6
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Weigand K, Singh N, Hagedorn M, Banert K. Direct observation and characterisation of 3-azido-2H-azirines: postulated, but highly elusive intermediates. Org Chem Front 2017. [DOI: 10.1039/c6qo00625f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The title compounds, including the parent 3-azido-2H-azirine, were generated by low-temperature photolysis of the corresponding 1,1-diazidoethenes, and characterised not only by trapping reactions, but also by direct detection using NMR and in situ IR spectroscopy.
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Affiliation(s)
- Kevin Weigand
- Chemnitz University of Technology
- Organic Chemistry
- 09111 Chemnitz
- Germany
| | - Neeraj Singh
- Chemnitz University of Technology
- Organic Chemistry
- 09111 Chemnitz
- Germany
| | - Manfred Hagedorn
- Chemnitz University of Technology
- Organic Chemistry
- 09111 Chemnitz
- Germany
| | - Klaus Banert
- Chemnitz University of Technology
- Organic Chemistry
- 09111 Chemnitz
- Germany
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7
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Kurosawa F, Nakano T, Soeta T, Endo K, Ukaji Y. (Z)-Selective Enol Triflation of α-Alkoxyacetoaldehydes: Application to Synthesis of (Z)-Allylic Alcohols via Cross-Coupling Reaction and [1,2]-Wittig Rearrangement. J Org Chem 2015; 80:5696-703. [PMID: 25970239 DOI: 10.1021/acs.joc.5b00647] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The stereoselective transformation of α-alkoxyacetoaldehydes to the corresponding (Z)-vinyl triflates was achieved by treatment with phenyl triflimide and DBU. The stereochemistry was explained by the "syn-effect," which was attributed primarily to an σ → π* interaction. The β-alkoxy vinyl triflates obtained were applied to the stereoselective synthesis of structurally diverse (Z)-allylic alcohols via transition metal-catalyzed cross-coupling reaction and [1,2]-Wittig rearrangement.
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Affiliation(s)
- Fumiya Kurosawa
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Takeo Nakano
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Takahiro Soeta
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Kohei Endo
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Yutaka Ukaji
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
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8
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Rokade BV, Gadde K, Prabhu KR. Copper-Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Srinu G, Srihari P. A catalytic approach for the synthesis of allylic azides from aryl vinyl carbinols. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2013.02.094] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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10
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Craig D, Harvey JW, O'Brien AG, White AJP. Claisen rearrangements of equilibrating allylic azides. Org Biomol Chem 2011; 9:7057-61. [PMID: 21879133 DOI: 10.1039/c1ob05972f] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Equilibrating mixtures of allylic azide-containing allylic alcohols or allylic 2-tolylsulfonylacetic esters undergo Johnson-Claisen or Ireland-Claisen rearrangement reactions to give unsaturated γ-azidoesters and -acids, respectively. Decarboxylation of the acids under basic conditions gives azidosulfones, with moderate to high diastereoselectivity.
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Affiliation(s)
- Donald Craig
- Department of Chemistry, Imperial College London, South Kensington Campus, London, UK SW7 2AZ.
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11
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Banert K, Meier B, Penk E, Saha B, Würthwein EU, Grimme S, Rüffer T, Schaarschmidt D, Lang H. Highly Strained 2,3-Bridged 2H-Azirines at the Borderline of Closed-Shell Molecules. Chemistry 2010; 17:1128-36. [DOI: 10.1002/chem.201002474] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Indexed: 11/06/2022]
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12
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Antonioletti R, Bonadies F, Ciammaichella A, Viglianti A. Lithium hydroxide as base in the Wittig reaction. A simple method for olefin synthesis. Tetrahedron 2008. [DOI: 10.1016/j.tet.2008.02.091] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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13
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Adil K, Bail AL, Dujardin G, Maisonneuve V. A new 1D hybrid fluoroaluminate templated by an original tetramine. Polyhedron 2007. [DOI: 10.1016/j.poly.2006.12.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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14
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Banert K, Grimme S, Herges R, Hess K, Köhler F, Mück-Lichtenfeld C, Würthwein EU. Experimental and Theoretical Characterization of the Valence Isomerization of Bi-2H-azirin-2-yls to Diazabenzenes. Chemistry 2006; 12:7467-81. [PMID: 16819722 DOI: 10.1002/chem.200600318] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
3,4-diazidocyclobutenes 16 were prepared from the corresponding dihalides. Some of these diazides, such as parent compound 16 d and phenyl-substituted derivatives 16 c,f, underwent spontaneous stereoselective electrocyclic ring opening below room temperature, whereas the tetraalkyl derivatives of 16 had to be heated to force the same reaction. In most cases, the resulting 1,4-diazidobuta-1,3-dienes 8 were isolated to study their photochemical transformation into bi-2H-azirin-2-yls 9 via intermediate mono-azirines 17. Except for starting materials with a low number of substituents such as 9 d and 9 f, title compounds 9 underwent a thermal valence isomerization which led exclusively to pyridazines 18 at surprisingly low temperatures. Based on quantum-chemical calculations for the parent bi-2H-azirinyl-2-yl 9 d at the UB3LYP/6-31+G(d) and MR-MP2/TZV(2df,2p) levels, the valence isomerization process is best explained by simultaneous homolytic cleavage of both C--N single bonds of 9 to generate energetically favorable N,N' diradicals 26, which cyclize to 18. The theoretical studies indicate also that one stereoisomer of 9, namely, the rac compound, should undergo valence isomerization more easily than the other, which is in conformity with different rates of these rearrangement reactions found experimentally. For the tetramethyl-bi-2H-azirin-2-yls 9 g, which are better models for the experimentally studied compounds, simultaneous homolytic cleavage of both C--N single bonds is also predicted by the calculations, although the intermediate diradicals 26 g are significantly higher in energy than those of the parent system 9 d.
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Affiliation(s)
- Klaus Banert
- Institut für Chemie der Technischen Universität Chemnitz, 09107 Chemnitz, Germany.
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15
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Banert K, Meier B. Synthesis and Reactions of Highly Strained 2,3-Bridged 2H-Azirines. Angew Chem Int Ed Engl 2006; 45:4015-9. [PMID: 16683290 DOI: 10.1002/anie.200600483] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Klaus Banert
- Lehrstuhl für Organische Chemie, Technische Universität Chemnitz, Strasse der Nationen 62, 09111 Chemnitz, Germany.
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16
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Banert K, Meier B. Synthese und Reaktionen hochgespannter 2,3-verbrückter 2H-Azirine. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200600483] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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17
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Rearrangement of allylic azide and phenylthio groups of 3′-azido- or 3′-phenylthio-4′,5′-didehydro-5′-deoxyarabinofuranosyluridines. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.08.092] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Heber D, Rösner P, Tochtermann W. Cyclooctyne and 4‐Cyclooctyn‐1‐ol – Versatile Building Blocks in Organic Synthesis. European J Org Chem 2005. [DOI: 10.1002/ejoc.200500288] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Dieter Heber
- Pharmazeutisches Institut der Universität Kiel, Gutenbergstr. 76, 24118 Kiel, Germany, Fax: +49‐431‐880‐1352
| | - Peter Rösner
- Institut für Organische Chemie der Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany, Fax: +49‐6398‐993172
| | - Werner Tochtermann
- Institut für Organische Chemie der Universität Kiel, Olshausenstr. 40, 24098 Kiel, Germany, Fax: +49‐6398‐993172
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19
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Baker-Glenn CA, Barrett AG, Gray AA, Procopiou PA, Ruston M. Alkene synthesis: elimination of arenesulfinic acid from alkyl aryl sulfones using potassium trimethylsilanolate as base. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.08.097] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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20
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Harayama T, Hori A, Serban G, Morikami Y, Matsumoto T, Abe H, Takeuchi Y. Concise synthesis of quinazoline alkaloids, luotonins A and B, and rutaecarpine. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.09.016] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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21
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Hölemann A, Reissig HU. Regioselective Samarium Diiodide Induced Couplings of Carbonyl Compounds with 1,3-Diphenylallene and Alkoxyallenes: A New Route to 4-Hydroxy-1-enol Ethers. Chemistry 2004; 10:5493-506. [PMID: 15372682 DOI: 10.1002/chem.200400418] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Since its introduction into synthetic organic chemistry, samarium diiodide has found broad application in a variety of synthetically important transformations. Herein, we describe the first successful intermolecular additions of samarium ketyls to typical allenes such as 1,3-diphenylallene (7), methoxyallene (12) and benzyloxyallene (25). Reaction of different samarium ketyls with 1,3-diphenylallene (7) occurred exclusively at the central carbon atom of the allene to afford products 9 in moderate to good yields. In contrast, reductive coupling of cyclic ketones to methoxyallene (12) regioselectively provided 4-hydroxy-1-enol ethers 13, which derive from addition to the terminal allene carbon atom of 12, in moderate to good yields. Whereas the E/Z selectivity with respect to the enol ether double bond is low, excellent diastereoselectivity has been observed in certain cases with regard to the ring configuration (e.g. compound 13 b). Studies with deuterated tetrahydrofuran and alcohol were performed to gain information about the reaction mechanism of this coupling process, which involves alkenyl radicals. The couplings of samarium ketyls derived from acyclic ketones and aldehydes gave lower yields, and in several cases cyclopentanols 20 are formed as byproducts. Branched acyclic ketones and conformationally more flexible cyclic ketones such as cycloheptanone led to a relatively high amount of cyclopentanol derivatives 20, whose formation involves an intramolecular hydrogen atom transfer through a geometrically favoured six-membered transition state followed by a cyclization step. The samarium diiodide mediated addition of 8 b to benzyloxyallene (25) afforded the expected enol ethers 26, albeit in only low yield. Additionally, spirocyclic compounds 27 and 28 were obtained, which are formed by a cascade reaction involving an addition/cyclization sequence. In the novel coupling process described here methoxyallene (12) serves as an equivalent of acrolein. The 1,4-dioxygenated products obtained contain a masked aldehyde functionality and are therefore valuable building blocks in organic synthesis.
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Affiliation(s)
- Alexandra Hölemann
- Institut für Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
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22
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Katritzky AR, Wang M, Wilkerson CR, Yang H. A Novel Approach to Substituted 2H-Azirines. J Org Chem 2003; 68:9105-8. [PMID: 14604388 DOI: 10.1021/jo034472i] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
2-(Benzotriazol-1-yl)-2H-azirines 4a-c, obtained by treatment of oximes 2a-c with tosyl chloride and aqueous KOH, were reacted with benzylmagnesium bromide or 4-methylbenzylmagnesium bromide in the presence of zinc chloride to give 2-benzyl-2H-azirines 5a-f. Potassium phthalimide and sodium salt of benzenethiol converted 2-(benzotriazol-1-yl)-2H-azirines 4a-c into novel 2H-azirines 6a-c and 7 in good yields.
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Affiliation(s)
- Alan R Katritzky
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA.
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23
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Palacios F, de Retana AMO, Martínez de Marigorta E, Manuel de los Santos J. PREPARATION, PROPERTIES AND SYNTHETIC APPLICATIONS OF 2H-AZIRINES A REVIEW. ORG PREP PROCED INT 2002. [DOI: 10.1080/00304940209356770] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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24
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Banert K, Köhler F. Synthese von 1,4-Diazidobuta-1,3-dienen durch elektrocyclische Ringöffnung: Vorstufen für Bi-2H-azirin-2-yle und deren Valenzisomerisierung zu Diazabenzolen. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20010105)113:1<173::aid-ange173>3.0.co;2-v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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25
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Banert K, Köhler F. Synthesis of 1,4-Diazidobuta-1,3-dienes by Electrocyclic Ring Opening: Precursors for Bi-2H-azirin-2-yls and Their Valence Isomerization to Diazabenzenes. Angew Chem Int Ed Engl 2001; 40:174-177. [DOI: 10.1002/1521-3773(20010105)40:1<174::aid-anie174>3.0.co;2-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2000] [Indexed: 11/06/2022]
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