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Rodriguez Treviño AM, Loch-Temzelides P, Pandiri S, Kirkland JK, Davenport MT, Aguinaga U, Yousufuddin M, Ess DH, Kürti L. Forging structural complexity: diastereoselective synthesis of densely substituted β-lactams with dual functional handles for enhanced core modifications. Chem Sci 2024:d4sc01513d. [PMID: 39170719 PMCID: PMC11332334 DOI: 10.1039/d4sc01513d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 07/31/2024] [Indexed: 08/23/2024] Open
Abstract
The preparation of the β-lactam motif containing both C-Br and N-O bonds as functional handles remains an unmet synthetic challenge. Described herein is a novel and highly diastereoselective NBS-mediated cyclization of N-alkoxy α,β-unsaturated silyl imino ethers to furnish nearly three dozen α-bromo N-alkoxy β-lactams. The reaction gives rapid and convenient access to structurally diverse monocyclic, spirocyclic and fused β-lactams in moderate to good yields. The two functional handles were shown to be useful for the further elaboration of the β-lactam core.
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Affiliation(s)
| | | | - Sanjay Pandiri
- Department of Chemistry, Rice University Houston Texas 77030 USA
| | - Justin K Kirkland
- Department of Chemistry and Biochemistry, Brigham Young University Provo Utah 84604 USA
| | - Michael T Davenport
- Department of Chemistry and Biochemistry, Brigham Young University Provo Utah 84604 USA
| | - Ulises Aguinaga
- Department of Natural Sciences, University of North Texas at Dallas Dallas Texas 75241 USA
| | - Muhammed Yousufuddin
- Department of Natural Sciences, University of North Texas at Dallas Dallas Texas 75241 USA
| | - Daniel H Ess
- Department of Chemistry and Biochemistry, Brigham Young University Provo Utah 84604 USA
| | - László Kürti
- Department of Chemistry, Rice University Houston Texas 77030 USA
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2
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Toyota M, Takabatake T, Yoneda T, Otsuka J, Kagawa N. Artificial Intelligence-Designed Stereoselective One-Pot Synthesis of trans-β-Lactams and Its Application to Cholesterol Absorption Inhibitor SCH 47949 Synthesis. HETEROCYCLES 2020. [DOI: 10.3987/com-19-14130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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3
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Artificial intelligence designed drug synthesis: One-pot preparation of trans β-lactams and application to cholesterol absorption inhibitor SCH 47949 synthesis. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.07.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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4
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Chatgilialoglu C, Ferreri C, Landais Y, Timokhin VI. Thirty Years of (TMS)3SiH: A Milestone in Radical-Based Synthetic Chemistry. Chem Rev 2018; 118:6516-6572. [DOI: 10.1021/acs.chemrev.8b00109] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | - Carla Ferreri
- ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy
| | - Yannick Landais
- University of Bordeaux, Institute of Molecular Sciences, UMR-CNRS 5255, 351 cours de la libération, 33405 Talence Cedex, France
| | - Vitaliy I. Timokhin
- Department of Biochemistry, University of Wisconsin-Madison, 1552 University Avenue, Madison, Wisconsin 53726, United States
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5
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Berry S, Bari SS, Banik BK, Bhalla A. Stereoselective synthesis of novel monocyclic trans-3-halogenated-4-pyrazolyl-β-lactams: Potential synthons and promising biologically active agents. SYNTHETIC COMMUN 2017. [DOI: 10.1080/00397911.2017.1371759] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Shiwani Berry
- Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, India
| | - Shamsher S. Bari
- Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, India
| | - Bimal K. Banik
- Community Health Systems of South Texas, Edinburg, TX, USA
| | - Aman Bhalla
- Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, India
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Esmaeilpour M, Sardarian AR, Jarrahpour A, Ebrahimi E, Javidi J. Synthesis and characterization of β-lactam functionalized superparamagnetic Fe3O4@SiO2 nanoparticles as an approach for improvement of antibacterial activity of β-lactams. RSC Adv 2016. [DOI: 10.1039/c6ra03634a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Preparation of magnetic β-lactam functionalized Fe3O4@SiO2 nanoparticles has a synergic effect to improve the antibacterial activity.
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Affiliation(s)
| | | | | | - Edris Ebrahimi
- Chemistry Department
- College of Sciences
- Shiraz University
- Shiraz
- Iran
| | - Jaber Javidi
- Department of Pharmaceutics
- School of Pharmacy
- Shahid Beheshti University of Medical Sciences
- Tehran
- Iran
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7
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Zarei M. Oxidative N-deprotection of 2-azetidinones using silver(II)–persulfate complexes as a twin oxidant/co-oxidant. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2013.05.124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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8
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9
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Long S, Monari M, Panunzio M, Bandini E, D'Aurizio A, Venturini A. Hetero-Diels-Alder (HDA) Strategy for the Preparation of 6-Aryl- and Heteroaryl-Substituted Piperidin-2-one Scaffolds: Experimental and Theoretical Studies. European J Org Chem 2011. [DOI: 10.1002/ejoc.201100930] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Lage ML, Fernández I, Sierra MA, Torres MR. Trapping Intermediates in an [8 + 2] Cycloaddition Reaction with the Help of DFT Calculations. Org Lett 2011; 13:2892-5. [DOI: 10.1021/ol200910z] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Marta L. Lage
- Departamento de Química Orgánica I and Laboratorio de Difracción de Rayos-X, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Israel Fernández
- Departamento de Química Orgánica I and Laboratorio de Difracción de Rayos-X, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Miguel A. Sierra
- Departamento de Química Orgánica I and Laboratorio de Difracción de Rayos-X, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - M. Rosario Torres
- Departamento de Química Orgánica I and Laboratorio de Difracción de Rayos-X, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
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11
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Mollet K, D’hooghe M, De Kimpe N. Transformation of trans-4-Aryl-3-chloro-1-(2-chloroethyl)azetidin-2-ones into 3-Aryl-2-(ethylamino)propan-1-ols via Intermediate 1-(1-Aryl-2-chloro-3-hydroxypropyl)aziridines and trans-2-Aryl-3-(hydroxymethyl)aziridines. J Org Chem 2010; 76:264-9. [DOI: 10.1021/jo1020932] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Karen Mollet
- Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Matthias D’hooghe
- Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Norbert De Kimpe
- Department of Sustainable Organic Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
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12
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Zarei M, Jarrahpour A. Synthesis of N-unsubstituted β-lactams from N-alkoxyphenyl-β-lactams with cobalt(III) fluoride. Tetrahedron Lett 2010. [DOI: 10.1016/j.tetlet.2010.08.101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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13
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Jarrahpour A, Zarei M. Efficient one-pot synthesis of 2-azetidinones from acetic acid derivatives and imines using methoxymethylene-N,N-dimethyliminium salt. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.05.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Affiliation(s)
- Bimal K. Banik
- Dept. Chemistry, University of Texas-Pan American, W. University Drive 1201, Edinburg, 78539 USA
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Jarrahpour A, Zarei M. Ceric Ammonium Nitrate on Silica Gel for Solid–Solid PhaseN-Dearylation of β -Lactams. PHOSPHORUS SULFUR 2009. [DOI: 10.1080/10426500802336630] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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17
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Hansen CP, Jensen AA, Christensen JK, Balle T, Liljefors T, Frølund B. Novel acetylcholine and carbamoylcholine analogues: development of a functionally selective alpha4beta2 nicotinic acetylcholine receptor agonist. J Med Chem 2009; 51:7380-95. [PMID: 18989912 DOI: 10.1021/jm701625v] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of carbamoylcholine and acetylcholine analogues were synthesized and characterized pharmacologically at neuronal nicotinic acetylcholine receptors (nAChRs). Several of the compounds displayed low nanomolar binding affinities to the alpha4beta2 nAChR and pronounced selectivity for this subtype over alpha3beta4, alpha4beta4, and alpha7 nAChRs. The high nAChR activity of carbamoylcholine analogue 5d was found to reside in its R-enantiomer, a characteristic most likely true for all other compounds in the series. Interestingly, the pronounced alpha4beta2 selectivities exhibited by some of the compounds in the binding assays translated into functional selectivity. Compound 5a was a fairly potent partial alpha4beta2 nAChR agonist with negligible activities at the alpha3beta4 and alpha7 subtypes, thus being one of the few truly functionally selective alpha4beta2 nAChR agonists published to date. Ligand-protein docking experiments using homology models of the amino-terminal domains of alpha4beta2 and alpha3beta4 nAChRs identified residues Val111(beta2)/Ile113(beta4), Phe119(beta2)/Gln121(beta4), and Thr155(alpha4)/Ser150(alpha3) as possible key determinants of the alpha4beta2/alpha3beta4-selectivity displayed by the analogues.
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Affiliation(s)
- Camilla P Hansen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, UniVersitetsparken 2, DK-2100 Copenhagen Ø, Denmark
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Cossío FP, Arrieta A, Sierra MA. The mechanism of the ketene-imine (staudinger) reaction in its centennial: still an unsolved problem? Acc Chem Res 2008; 41:925-36. [PMID: 18662024 DOI: 10.1021/ar800033j] [Citation(s) in RCA: 166] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[Reaction: see text]. Although Staudinger reported the reaction between ketenes and imines 100 years ago (1907), this process is still the most general and useful method for the synthesis of beta-lactams and their derivatives. This reaction is a [2 + 2] thermal cycloaddition in which two chiral centers may be generated in one preparative step. Staudinger reactions involving alpha,beta-unsaturated imines or ketenes have issues concerning the [2 + 2] or [4 + 2] periselectivity of the reaction. This Account discusses how the main factors that determine the regiochemical and stereochemical outcomes of this reaction were elucidated with computational and experimental data. This fruitful interplay between theory and experiment has revealed that the [2 + 2] cycloaddition is actually a two-step process. The first step is a nucleophilic addition of the nitrogen atom of the imine on the sp-hybridized carbon atom of the ketene. This attack forms a zwitterionic intermediate that evolves toward the final beta-lactam cycloadduct. The second step can be viewed as a four-electron conrotatory electrocyclization that is subject to torquoelectronic effects. When alpha,beta-unsaturated imines are used, the zwitterionic intermediates yield either the corresponding 4-vinyl-beta-lactams or the alternative 3,4-dihydropyridin-2(1 H)-ones. In this latter case, the cyclization step consists of a thermal disrotatory electrocyclization. In the context of stereoselectivity, it is usually assumed that the first step takes place through the less hindered side of the ketene. The cis-trans selectivity of the reaction depends on the geometry of the imine. As the general rule, ( E)-imines form cis-beta-lactams whereas ( Z)-imines yield trans-beta-lactams. Most of the experimental results point to the two-step model. The asymmetric torquoselectivity of the conrotatory ring closure of the second step accounts for the stereochemical discrimination in the reaction of chiral ketenes or chiral imines. Nevertheless, recent studies have revealed that isomerization paths in the imine or in the zwitterion may determine the stereochemistry of the reaction. Thus, if the rotation about the N1-C4 bond of the zwitterion intermediate is faster than the cyclization, the formation of trans-beta-lactams from ( E)-imines is biased. Alternatively, in some cases, the ( E)-( Z) isomerization of the starting imines prior to the cycloaddition steps also results in the formation of trans-cycloadducts. Although the main variables that govern the outcome of the reaction have been elucidated, there are still several aspects of the reaction yet to be disclosed. Finally, the discovery of the catalytic version of the reaction is a new and formidable mechanistic challenge and will be a nice playground for forthcoming theoretical-experimental discussions.
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Affiliation(s)
- Fernando P. Cossío
- Departamento de Química Orgánica I, Universidad del País Vasco-Euskal Herriko Unibertsitatea. Ap 1072, 20080, San Sebastián-Donostia, Spain
| | - Ana Arrieta
- Departamento de Química Orgánica I, Universidad del País Vasco-Euskal Herriko Unibertsitatea. Ap 1072, 20080, San Sebastián-Donostia, Spain
| | - Miguel A. Sierra
- Departamento de Química Orgánica, Facultad de Química, Universidad Complutense, 28040-Madrid, Spain
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Sun C, Lin X, Weinreb SM. Explorations on the Total Synthesis of the Unusual Marine Alkaloid Chartelline A. J Org Chem 2006; 71:3159-66. [PMID: 16599614 DOI: 10.1021/jo060084f] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In work directed toward a total synthesis of chartelline A (1a), a strategy was investigated to construct the 10-membered ring of this marine alkaloid via an intramolecular aldehyde/beta-lactam cyclocondensation to form the macrocyclic enamide functionality. Therefore, spiro-beta-lactam and imidazole fragments were first prepared. Tribromooxindole beta-lactam 24 was synthesized from commercially available 5-nitroisatin (18) in seven steps and 30% overall yield via a Staudinger ketene-imine [2 + 2]-cycloaddition strategy. The requisite 2-bromoimidazole subunit 40 bearing a terminal alkyne and a masked aldehyde was efficiently prepared from the readily available imidazole ester 25 in 10 steps. With both advanced intermediates available, the addition of the lithium acetylide generated from 2-bromoimidazole subunit 40 to the gamma-lactam carbonyl group of N-Boc-tribromooxindole 24 was investigated, affording the desired N-Boc-aminal 41. Hydrolysis of the acetonide moiety of 41, followed by oxidative cleavage of the resulting diol, gave the aldehyde 42. Unfortunately, treatment of aldehyde 42 with p-toluenesulfonic acid did not give the desired 10-membered macrocyclic (Z)-enamide 46, but rather the highly unsaturated seven-membered ring compound 44.
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Affiliation(s)
- Cuixiang Sun
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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20
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Campomanes P, Menéndez MI, Sordo TL. Mechanism of Cycloaddition Reactions between Ketene and N-Silyl-, N-Germyl-, and N-Stannylimines: A Theoretical Investigation. J Phys Chem A 2005; 109:11022-6. [PMID: 16331946 DOI: 10.1021/jp054103l] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A theoretical study of the cycloaddition reactions of ketene and N-silyl-, N-germyl-, and N-stannylimines were performed at the B3LYP/6-311+G(d,p) theory level using the LANL2DZ effective core potential for Ge and Sn and taking into account the effect of diethyl ether solvent by means of the polarizable continuum model method. According to the obtained results the reaction between ketene and N-germylimine is a two-step process due to the effect of solvent, whereas the cycloaddition of ketene and N-silylimine follows a three-step mechanism because in this case the evolution of the electronic energy along the reaction coordinate predominates over the effect of solvent. For N-stannylimine the two- and three-step mechanisms are competitive. In all the cases the rate-determining barrier corresponds to the evolution of the azadiene intermediate. The cycloaddition of ketene and N-germylimine is kinetically the most favorable reaction of the three studied by us and can take place as a domino process. In the three cases the isomerization of the imine through the inversion at the nitrogen atom is easier than the formation of the azadiene intermediate so that the three processes would afford the trans-beta-lactam.
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Affiliation(s)
- Pablo Campomanes
- Departamento de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, C/Julián Clavería, 8, 33006 Oviedo, Principado de Asturias, Spain
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Panunzio M, Bongini A, Monari M, Tamanini E, Bandini E. Convergent synthesis of cis-α,β-epoxy-carboxylic acids from 1-halo-2-trimethylsilyloxy-3-aza-4-phenyl-1,3-butadiene. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.07.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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22
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Panunzio M, Bongini A, Tamanini E, Campana E, Martelli G, Vicennati P, Zanardi I. Synthesis of NH -3-phenylsulfanyl- and NH -3-benzylsulfanyl-azetidinones from 1-phenylsulfanyl- or 1-benzylsulfanyl-3-aza-1,3-dienes. Tetrahedron 2003. [DOI: 10.1016/j.tet.2003.10.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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23
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24
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Bongini A, Panunzio M, Tamanini E, Martelli G, Vicennati P, Monari M. Lewis acid-catalyzed electrocyclization of 2-aza-1,3-butadienes to NH-β-lactams. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0957-4166(03)00162-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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25
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Synthesis of 4-aryl-substituted β-lactam enantiomers by enzyme-catalyzed kinetic resolution. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0957-4166(01)00388-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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26
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Model studies on total synthesis of the chartellines, spirocyclic β-lactam alkaloids from a marine bryozoan. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)00270-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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27
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Bongini A, Panunzio M, Bandini E, Campana E, Martelli G, Spunta G. Synthesis of perhydroxazin-4-ones. Competitive Mukaiyama versus hetero Diels–Alder reaction in the cycloaddition of 2-aza-3-trimethylsilyloxy-1,3-butadiene and aldehydes. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0957-4166(01)00051-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Arrieta A, Cossío FP, Lecea B. New insights on the origins of the stereocontrol of the staudinger reaction: [2 + 2] cycloaddition between ketenes and N-silylimines. J Org Chem 2000; 65:8458-64. [PMID: 11112564 DOI: 10.1021/jo0007736] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density-functional theory studies on the [2 + 2] reaction between N-silylimines and ketenes to form the corresponding 2-azetidinones (beta-lactams) help to clarify several aspects on the mechanism of the Staudinger reaction. This reaction has been studied experimentally by Panunzio et al. It is shown that the formation of the 2-azetidinone ring takes place via two consecutive reactions. The first reaction consists of the nucleophilic addition of the iminic nitrogen to the sp-hybridized carbon atom of the ketene, with simultaneous migration of the silyl group from the imine to the oxygen atom of the ketene. This leads to silyl enol intermediates, in good agreement with the experimental results. Formation of the N-silylated beta-lactam takes place via a domino reaction consisting of a conrotatory thermal electrocyclization followed by a new silatropic rearrangement. It is also found that isomerization of the starting N-silylimine has a lower activation barrier than that associated with the formation of the C-N bond, which explains the stereochemical outcome experimentally observed. Further considerations on the asymmetric torquoelectronic effects involved in this reaction are also reported.
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Affiliation(s)
- A Arrieta
- Farmazi Fakultatea, Euskal Herriko Unibertsitatea, P.K. 450, 01080 Vitoria-Gasteiz, Spain
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