1
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Creary X. The cyclopropylcarbinyl route to γ-silyl carbocations. Beilstein J Org Chem 2019; 15:1769-1780. [PMID: 31435448 PMCID: PMC6664402 DOI: 10.3762/bjoc.15.170] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 07/03/2019] [Indexed: 01/20/2023] Open
Abstract
The mesylate derivative of cis-1-hydroxymethyl-2-trimethylsilylcyclopropane has been prepared, along with a number of related mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinyl cations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing (CF3, CN, or CO2CH3), significant amounts of bicyclobutane products are formed. The bicyclobutanes are a result of γ-trimethylsilyl elimination from the cationic intermediate that has an unusually long calculated Si–C bond. The solvolysis chemistry of mesylate and triflate derivatives of trans-1-hydroxymethyl-2-trimethylsilylcyclopropane and 1-substituted analogs can be quite different since these substrates do not generally lead to 3-trimethylsilylcyclobutyl cations.
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Affiliation(s)
- Xavier Creary
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 45556, USA
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2
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Nielsen CDT, Mooij WJ, Sale D, Rzepa HS, Burés J, Spivey AC. Reversibility and reactivity in an acid catalyzed cyclocondensation to give furanochromanes - a reaction at the 'oxonium-Prins' vs. ' ortho-quinone methide cycloaddition' mechanistic nexus. Chem Sci 2019; 10:406-412. [PMID: 30713643 PMCID: PMC6334628 DOI: 10.1039/c8sc04302g] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 10/18/2018] [Indexed: 01/23/2023] Open
Abstract
Herein we report a combined experimental and computational investigation of the acid catalyzed cyclocondensation reaction between styrenyl homoallylic alcohols and salicylaldehyde to form furanochromanes. We disclose a previously unreported isomerisation of the 'unnatural' trans-fused products to the diastereomeric 'natural' cis-fused congeners. Notwithstanding the appeal of assuming this corresponds to endo to exo isomerisation of Diels-Alder (D-A) adducts via concerted retro-cycloaddition/cycloaddition reactions of an in situ generated ortho-quinone methide with the styrenyl alkene, our combined Hammett/DFT study reveals a stepwise Prins-like process via discrete benzylic carbocation intermediates for all but the most electron deficient styrenes. As these reactions fortuitously lie at the intersection of these two mechanistic manifolds, it allows us to propose an experimentally determined indicative ρ + value of ca. -3 as marking this nexus between a stepwise Prins-type pathway and a concerted cycloaddition reaction. This value should prove useful for categorising other reactions formally involving 'ortho-quinomethides', without the need for the extensive computation performed here. Logical optimisation of the reaction based upon the mechanistic insight led to the use of HFIP as an additive which enables exclusive formation of 'natural' cis-fused products with a ∼100-fold reaction rate increase and improved scope.
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Affiliation(s)
- Christian D-T Nielsen
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Wouter J Mooij
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - David Sale
- Process Studies Group , Syngenta , Jealott's Hill , Bracknell , Berkshire RG42 6EY , UK
| | - Henry S Rzepa
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Jordi Burés
- School of Chemistry , University of Manchester , Oxford Road , Manchester , M13 9PL , UK
| | - Alan C Spivey
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
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3
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Zhu YJ, Wu QF, Fan ZJ, Huo JQ, Zhang JL, Zhao B, Lai C, Qian XL, Ma DJ, Wang DW. Synthesis, bioactivity and mode of action of 5 A 5 B 6 C tricyclic spirolactones as novel antiviral lead compounds. PEST MANAGEMENT SCIENCE 2019; 75:292-301. [PMID: 29885056 DOI: 10.1002/ps.5115] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/16/2018] [Accepted: 06/04/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Plant viral diseases cause tremendous decreases in yield and quality. Natural polycyclic compounds such as those containing carbocycles are often very important lead compounds for drug and pesticide development. Tricyclic spiranoid lactones with 5A 5B 6C -ring fusion topologies possess various bioactivities. In this study, 33 new 5A 5B 6C tricyclic spirolactones were rationally designed, synthesized, characterized and evaluated for antiviral activities. RESULT These compounds showed no apparent toxicity against Italian honeybees up to 2.73 µg bee-1 . Spirolactones 14, 16, 19, 23 and 28 at a concentration of 100 µg mL-1 inactivated 90% of tobacco mosaic virus (TMV) infection, making these compounds much more potent than the positive controls. Significantly, compound 19 displayed the best inactivation activity causing inhibition of up to 98%. CONCLUSION The results of the bioassays and QSAR studies indicated that the carbon-containing cyclic moiety was the antiviral pharmacophore, and derivative 19, which showed the best inactivation activity, could emerge as a potential antiviral agent against TMV. In vitro capsid protein (CP) assembly and TMV assembly inhibition determinations indicated that these compounds induced crosslinking in the TMV and prevented its uncoating, which was a putative new mode of action for TMV inactivation. © 2018 Society of Chemical Industry.
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Affiliation(s)
- Yu-Jie Zhu
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - Qi-Fan Wu
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - Zhi-Jin Fan
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, P. R. China
| | - Jing-Qian Huo
- College of Plant Protection, Agricultural University of Hebei, Baoding, P. R. China
| | - Jin-Lin Zhang
- College of Plant Protection, Agricultural University of Hebei, Baoding, P. R. China
| | - Bin Zhao
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - Chen Lai
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - Xiao-Lin Qian
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - De-Jun Ma
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
| | - Da-Wei Wang
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin, P. R. China
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4
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Kazakova AA, Bogomazova AA, Iakovenko RO, Zlotsky SS, Vasilyev AV. TfOH promoted reactions of vinyl gem- dichlorocyclopropanes with arenes: access to aryl gem -dichloropentenes. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.08.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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5
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Kelly CB, Mercadante MA, Carnaghan ER, Doherty MJ, Fager DC, Hauck JJ, MacInnis AE, Tilley LJ, Leadbeater NE. Synthesis of Perfluoroalkyl-Substituted Vinylcyclopropanes by Way of Enhanced Neighboring Group Participation. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500565] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Creary X, Heffron A, Going G, Prado M. γ-Trimethylsilylcyclobutyl carbocation stabilization. J Org Chem 2015; 80:1781-8. [PMID: 25562368 DOI: 10.1021/jo502691t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A series of isomeric 3-trimethylsilyl-1-arylcyclobutyl carbocations, 10 and 11, where the cross-ring 3-trimethylsilyl group has the potential to interact with the cationic center, have been generated under solvolytic conditions. When the cationic center can interact with the rear lobe of the carbon-silicon bond, rate enhancements become progressively larger as the substituent on the aryl group becomes more electron-withdrawing. When the potential interaction with the trimethylsilyl group is via a front lobe interaction, there is minimal rate enhancement over the range of substituents. Computational studies have also been carried out on these cations 10 and 11. Calculated trimethylsilyl stabilization energies progressively increase with electron-withdrawing character of the aryl groups when the trimethylsilyl interaction is via the rear lobe. By way of contrast, there are minimal changes in stabilization energies when the potential trimethylsilyl interaction is via the front lobe of the carbon-silicon bond. These computational studies, along with the solvolytic studies, point to a significant rear lobe 3-trimethylsilyl stabilization of arylcyclobutyl cations. They also argue against any front lobe stabilization of the isomeric arylcyclobutyl cations.
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Affiliation(s)
- Xavier Creary
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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McGrath JM, Pluth MD. Linear free energy relationships reveal structural changes in hydrogen-bonded host-guest interactions. J Org Chem 2014; 79:11797-801. [PMID: 25412431 PMCID: PMC4260963 DOI: 10.1021/jo502325w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
![]()
Hydrogen bond strength
in host–guest systems is modulated
by many factors including preorganization, steric effects, and electronic
effects. To investigate how electronic effects impact barbiturate
binding in bifurcated Hamilton receptors, a library of receptors with
differing electronic substituents was synthesized and 1H NMR titrations were performed with diethyl barbital. The Hammett
plot revealed a clear break between the different electronic substituents
suggesting a change in binding conformation. The titration data were
complimented with computational studies confirming the change in structure.
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Affiliation(s)
- Jacqueline M McGrath
- Department of Chemistry and Biochemistry, Materials Science Institute, University of Oregon , Eugene, Oregon 97403-1253, United States
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8
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Abstract
endo-2-Trimethylsilyl-anti-7-norbornyl triflate undergoes solvolysis reactions 1.8 × 10(4) faster than 7-norbornyl triflate in CD3CO2D and 1.3 × 10(5) times faster in CF3CH2OH. The exclusive substitution products with retained stereochemistry point to a significantly stabilized γ-trimethylsilyl carbocation intermediate. The endo-2-trimethylsilyl-7-norbornyl carbene gives a major rearrangement product where the trimethylsilyl-activated hydrogen migrates to the carbenic center. This rearrangement product implies stabilization of the carbene by the γ-trimethylsilyl group. Isodesmic computational studies (M062X/6-311+G**) indicate that the endo-2-trimethylsilyl-7-norbornyl cation is stabilized by 16.2 kcal/mol and that the endo-2-trimethylsilyl-7-norbornyl carbene is stabilized by a smaller factor of 1.8 kcal/mol. By way of contrast, anti-7-trimethylsilyl-endo-2-norbornyl mesylate undergoes solvolysis in CD3CO2D only 2.6 times faster than endo-2-norbornyl mesylate and 9.4 times faster in CF3CH2OH. The substitution products have only partially retained stereochemistry, and significant rearrangements are observed. The anti-7-trimethylsilyl-2-norbornyl carbene gives a rearrangement product via 1,3-hydrogen migration of the C6 hydrogen, which is completely analogous to the behavior of the unsubstituted 2-norbornyl carbene. Isodesmic calculations show that the anti-7-trimethylsilyl-2-norbornyl cation is stabilized by only 3.2 kcal/mol relative to the 2-norbornyl cation, and the corresponding anti-7-trimethylsilyl-2-norbornyl carbene is stabilized by a negligible 0.9 kcal/mol.
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Affiliation(s)
- Xavier Creary
- Department of Chemistry and Biochemistry University of Notre Dame , Notre Dame, Indiana 46556, United States
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9
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Creary X. 3-Trimethylsilylcyclobutylidene. The γ-effect of silicon on carbenes. J Am Chem Soc 2013; 135:6570-8. [PMID: 23527580 DOI: 10.1021/ja400747u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
3-Trimethylsilylcyclobutylidene was generated by pyrolysis of the sodium salt of the tosylhydrazone derivative of 3-trimethylsilylcyclobutanone. This carbene converts to 1-trimethylsilylbicyclobutane as the major product. A labeling study shows that this intramolecular rearrangement product comes from 1,3-hydrogen migration to the carbenic center and not 1,3-silyl migration. Computational studies show two carbene minimum energy conformations, with the lower energy conformation displaying a large stabilizing interaction of the carbene center with the rear lobe of the C3-Si bond. In this conformation, the trimethylsilyl group cannot migrate to the carbene center, and the most favorable process is 1,3-hydrogen migration. When the carbene is generated photochemically in methanol, it reacts by a protonation mechanism giving the highly stabilized 3-trimethylsilylcyclobutyl carbocation as an intermediate. When generated in dimethylamine as solvent, the carbene undergoes preferred attack of this nucleophilic solvent from the back of this C-Si rear lobe stabilized carbene.
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Affiliation(s)
- Xavier Creary
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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10
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Bag SS, Kundu R, Basak A, Slanina Z. Suppressed beta-effect of silicon in 3-silylated monocyclic beta-lactams: the role of antiaromaticity. Org Lett 2009; 11:5722-5. [PMID: 19916530 DOI: 10.1021/ol902411r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The beta-stabilizing effect of silicon substituent at C-3 on a C-4 cation and a radical in the 2-azetidinone systems is studied using NMR kinetics. While the beta-effect is virtually nonexistent in the case of a cation, a foiled beta-effect (only a 3-fold rate enhancement) is observed for a radical intermediate. From both the experimental and theoretical studies, it is demonstrated that antiaromaticity is playing the prime role in suppressing the beta-stabilizing effect of silicon.
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Affiliation(s)
- Subhendu Sekhar Bag
- Department of Chemistry, Indian Institute of Technology, Guwahati-781039, India.
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11
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Ring-closing metathesis for the synthesis of novel 9- and 10-membered silicon-containing benzo-fused heterocycles. Tetrahedron Lett 2008. [DOI: 10.1016/j.tetlet.2008.10.067] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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