1
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Müller DS, Charki P, Cordier M, Gellrich U. Utilization of 13C NMR Carbon Shifts for the Attribution of Diastereomers in Methyl-Substituted Cyclohexanes. J Org Chem 2024; 89:8668-8675. [PMID: 38856090 DOI: 10.1021/acs.joc.4c00602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
In this report, we address the challenge of assigning diastereomers for methyl cyclohexanes, particularly those with quaternary centers, which remains nontrivial despite modern NMR techniques. By utilizing a HSQC NMR experiment to identify methyl-carbons coupled with a simple conformational analysis, we identified an effective and quite general method for assigning stereochemistry, even in cases where diastereomeric mixtures are inseparable.
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Affiliation(s)
- Daniel S Müller
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR 6226, F-35000 Rennes, France
| | - Paul Charki
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR 6226, F-35000 Rennes, France
| | - Marie Cordier
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR 6226, F-35000 Rennes, France
| | - Urs Gellrich
- Department of Organic Chemistry, University of Hohenheim, Garbenstrasse 30, 70599 Stuttgart, Germany
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2
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Zeng Z, Kociok‐Köhn G, Woodman TJ, Rowan MG, Blagbrough IS. Structural Studies of Norditerpenoid Alkaloids: Conformation Analysis in Crystal and in Solution States. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100179] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ziyu Zeng
- Department of Pharmacy and Pharmacology University of Bath Bath BA2 7AY UK
| | - Gabriele Kociok‐Köhn
- Material and Chemical Characterisation Facility University of Bath Bath BA2 7AY UK
| | - Timothy J. Woodman
- Department of Pharmacy and Pharmacology University of Bath Bath BA2 7AY UK
| | - Michael G. Rowan
- Department of Pharmacy and Pharmacology University of Bath Bath BA2 7AY UK
| | - Ian S. Blagbrough
- Department of Pharmacy and Pharmacology University of Bath Bath BA2 7AY UK
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3
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Yu C, Kütt A, Röschenthaler G, Lebl T, Cordes DB, Slawin AMZ, Bühl M, O'Hagan D. Janus Face All-cis 1,2,4,5-tetrakis(trifluoromethyl)- and All-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)- Cyclohexanes. Angew Chem Int Ed Engl 2020; 59:19905-19909. [PMID: 32691941 PMCID: PMC7693182 DOI: 10.1002/anie.202008662] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Indexed: 02/03/2023]
Abstract
We report the synthesis of all-cis 1,2,4,5-tetrakis (trifluoromethyl)- and all-cis 1,2,3,4,5,6-hexakis (trifluoromethyl)- cyclohexanes by direct hydrogenation of precursor tetrakis- or hexakis- (trifluoromethyl)benzenes. The resultant cyclohexanes have a stereochemistry such that all the CF3 groups are on the same face of the cyclohexyl ring. All-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)cyclohexane is the most sterically demanding of the all-cis hexakis substituted cyclohexanes prepared to date, with a barrier (ΔG) to ring inversion calculated at 27 kcal mol-1 . The X-ray structure of all-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)cyclohexane displays a flattened chair conformation and the electrostatic profile of this compound reveals a large diffuse negative density on the fluorine face and a focused positive density on the hydrogen face. The electropositive hydrogen face can co-ordinate chloride (K≈103 ) and to a lesser extent fluoride and iodide ions. Dehydrofluorination promoted decomposition occurs with fluoride ion acting as a base.
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Affiliation(s)
- Cihang Yu
- School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - Agnes Kütt
- Department of Life Sciences and ChemistryJacobs University Bremen, gGmbHP.O. Box 750 56128725BremenGermany
- University of TartuInstitute of ChemistryRavila 14a50411TartuEstonia
| | - Gerd‐Volker Röschenthaler
- Department of Life Sciences and ChemistryJacobs University Bremen, gGmbHP.O. Box 750 56128725BremenGermany
| | - Tomas Lebl
- School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - David B. Cordes
- School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | | | - Michael Bühl
- School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
| | - David O'Hagan
- School of ChemistryUniversity of St AndrewsNorth HaughSt AndrewsKY16 9STUK
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4
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Yu C, Kütt A, Röschenthaler G, Lebl T, Cordes DB, Slawin AMZ, Bühl M, O'Hagan D. Janus Face All‐
cis
1,2,4,5‐tetrakis(trifluoromethyl)‐ and All‐
cis
1,2,3,4,5,6‐hexakis(trifluoromethyl)‐ Cyclohexanes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008662] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Cihang Yu
- School of Chemistry University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - Agnes Kütt
- Department of Life Sciences and Chemistry Jacobs University Bremen, gGmbH P.O. Box 750 561 28725 Bremen Germany
- University of Tartu Institute of Chemistry Ravila 14a 50411 Tartu Estonia
| | - Gerd‐Volker Röschenthaler
- Department of Life Sciences and Chemistry Jacobs University Bremen, gGmbH P.O. Box 750 561 28725 Bremen Germany
| | - Tomas Lebl
- School of Chemistry University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - David B. Cordes
- School of Chemistry University of St Andrews North Haugh St Andrews KY16 9ST UK
| | | | - Michael Bühl
- School of Chemistry University of St Andrews North Haugh St Andrews KY16 9ST UK
| | - David O'Hagan
- School of Chemistry University of St Andrews North Haugh St Andrews KY16 9ST UK
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5
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Nori-Shargh D, Amini MM, Jafari M, Deyhimi F, Jameh-Bozorghi S. Ab Initio Study of Geminal Steric Hindrance Effects on the Stability of Conformations of Cyclohexane Derivatives. JOURNAL OF CHEMICAL RESEARCH 2019. [DOI: 10.3184/030823405774663219] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ab initio and density functional theory methods (HF/3-21G*//HF/3-21G*, MP2/3-21G*//HF/3-21G*, B3LYP/3-21G*//HF/3-21G*, B3LYP/LANL2DZ*//HF/LANL2DZ*, MP2/LANL2DZ*//HF/LANL2DZ* and HF/LANL2DZ*//HF/LANL2DZ*) used to investigate the conformational properties of cyclohexane, 1,1-dimethylcyclohexane, 1,1-di-tert-butylcyclohexane, 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane and 1,1-bis(trimethylstannyl)cyclohex ane showed that the energy difference between the chair and twist-boat conformations and also the ring flipping energy barrier decreases from cyclohexane, 1,1-dimethylcyclohexane to 1,1-di-tert-butylcyclohexane, and increases from 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane to 1,1-bis(trimethylstannyl)cyclohexane.
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Affiliation(s)
- Davood Nori-Shargh
- Chemistry Department, Graduate Faculty, Arak branch, Islamic Azad University, Arak, Iran
- Chemistry Department, Science and Research Campus, Islamic Azad University, Hesarak, Poonak, Tehran, Iran
| | | | - Maryam Jafari
- Chemistry Department, Graduate Faculty, Arak branch, Islamic Azad University, Arak, Iran
| | - Farzad Deyhimi
- Chemistry Department, Shahid Beheshti University, Evin-Tehran 19839, Iran
| | - Saeed Jameh-Bozorghi
- Chemistry Department, Graduate Faculty, Arak branch, Islamic Azad University, Arak, Iran
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6
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Sławek A, Grzybowska K, Vicent-Luna JM, Makowski W, Calero S. Adsorption of Cyclohexane in Pure Silica Zeolites: High-Throughput Computational Screening Validated by Experimental Data. Chemphyschem 2018; 19:3364-3371. [PMID: 30457696 DOI: 10.1002/cphc.201800968] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Indexed: 11/09/2022]
Abstract
Adsorption of cyclohexane in pure silica zeolites was studied experimentally and by molecular simulations. Based on the adsorption isobars obtained from the quasi-equilibrated temperature adsorption and desorption (QE-TPDA) measurements and reported adsorption isotherms for high-silica zeolites Y, ZSM-5, and ZSM-11 we refined Lennard-Jones parameters for guest-host interactions available in the literature. Adsorption of cyclohexane from equimolar mixture of twisted-boat and chair conformations has been screened in 171 pure silica zeolitic structures using grand canonical Monte Carlo simulations. Almost 20 frameworks showing extraordinary preference for adsorption of the chair conformation over the twisted boat one or vice versa were found. This selectivity was attributed to the geometry of channels and cavities present in the pore structures, as all t-boat selective structures possess channels or cavities of 8.3-9.1 Å. We also differentiated ways of chair-selectivity depending on the size and shape of the channels or cavities and also on the arrangement of the guest molecules in the pores.
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Affiliation(s)
- Andrzej Sławek
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - Karolina Grzybowska
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - José Manuel Vicent-Luna
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1. ES-41013, Seville, Spain
| | - Wacław Makowski
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland
| | - Sofía Calero
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1. ES-41013, Seville, Spain
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7
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Dhanju S, Blazejewski BW, Crich D. Synthesis of Trialkylhydroxylamines by Stepwise Reduction of O-Acyl N,N-Disubstituted Hydroxylamines: Substituent Effects on the Reduction of O-(1-Acyloxyalkyl)hydroxylamines and on the Conformational Dynamics of N-Alkoxypiperidines. J Org Chem 2017; 82:5345-5353. [DOI: 10.1021/acs.joc.7b00717] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sandeep Dhanju
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | | | - David Crich
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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8
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Synthesis and Desymmetrization of meso-2,3-Diphenylpiperazine for Application in Asymmetric Transformations. ChemistrySelect 2017. [DOI: 10.1002/slct.201700488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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9
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Bain AD, Baron M, Burger SK, Kowalewski VJ, Rodríguez MB. Interconversion study in 1,4-substituted six-membered cyclohexane-type rings. Structure and dynamics of trans-1,4-dibromo-1,4-dicyanocyclohexane. J Phys Chem A 2011; 115:9207-16. [PMID: 21786756 DOI: 10.1021/jp205375f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyclohexane is an extremely flexible molecule that oscillates, at room temperature, between two clearly distinct and extreme conformations that cannot be distinguished at room temperature; so much so that the NMR spectrum is a single line that includes all 12 protons be they axial or equatorial. This raises the interesting question as to what happens when there are equal substituents at the 1 and 4 carbon atoms of the ring. Therefore substitution in the 1,4-positions in the cyclohexane ring has been the subject of considerable interest because some form of interconversion between extreme conformations could lead to the existence of a rather unusual behavior. To study this problem, the interconversion in (di- or tetra-1,4)-substituted six-membered cyclohexane-type rings, trans-1,4-dibromo-1,4-dicyanocyclohexane, was found to be a particularly suitable candidate. Although X-ray diffraction studies on the crystalline solid found the molecule to be centrosymmetric, it still shows a significant dipole moment μ in solution, as determined with a procedure that leads to the vapor phase values of μ. Furthermore, the low magnetic field proton NMR spectrum at ambient temperature appears as a single line, a situation that changes with increasing field intensity and different solvents. Both these effects are attributed to dynamics, because small distortions can easily disrupt the exact cancellation of the individual dipoles (which are quite strong) associated with each end of the molecule. The molecule can exist in two forms, with both the bromines in an axial geometry or both in an equatorial position. Interconversion between these forms is observed, as in the parent cyclohexane. The single NMR line observed at low magnetic fields is due to fast exchange and requires that the two forms have roughly equal populations. Spectra obtained at low temperature confirm this, and variable-temperature studies allow measurement of the rates, leading to an enthalpy of activation of 62 kJ mol(-1). More details of the interconversion are provided by some new calculation methods. Even for a relatively small molecule like this, calculation of a full potential energy surface is prohibitive. However, methods are now available to follow the molecule along the reaction coordinate in quite an efficient way. The results of these calculations lead to an extremely detailed picture of chair-chair interconversion in a di- and tetrasubstituted six-membered ring of the cyclohexane family.
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Affiliation(s)
- Alex D Bain
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
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10
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Yang H, Carter RG. Development of an enantioselective route toward the Lycopodium alkaloids: total synthesis of lycopodine. J Org Chem 2010; 75:4929-38. [PMID: 20586477 PMCID: PMC2943527 DOI: 10.1021/jo100916x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synthesis of a C(15)-desmethyl tricycle core of lycopodine has been accomplished. Key steps in the synthetic sequence include organocatalytic, intramolecular Michael addition of a keto sulfone and a tandem 1,3-sulfonyl shift/Mannich cyclization to construct the tricyclic core ring system. Synthetic work toward this natural product family led to the development of N-(p-dodecylphenylsulfonyl)-2-pyrrolidinecarboxamide, an organocatalyst which facilitates enantioselective, intramolecular Michael additions. A detailed mechanistic discussion is provided for both the intramolecular Michael addition and the sulfone rearrangement. Finally, the application of these discoveries to the enantioselective total synthesis of alkaloid lycopodine is described.
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Affiliation(s)
- Hua Yang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
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11
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Quadrelli P, Mella M, Carosso S, Bovio B, Caramella P. A Straightforward Synthesis of Isoxazoline-Based Carbocyclic Nucleosides from 1,3-Cyclohexadiene through Nitrosocarbonyl Chemistry. European J Org Chem 2007. [DOI: 10.1002/ejoc.200700569] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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12
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Shlykov SA, Giricheva NI, Eyler GN, Oberhammer H. Gas-Phase Structure and Conformational Properties of 3,3,6,6-Tetramethyl-1,2,4,5-Tetroxane. J Phys Chem A 2007; 111:1368-73. [PMID: 17260979 DOI: 10.1021/jp067763e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The geometric structure and conformational properties of 3,3,6,6-tetramethyl-1,2,4,5-tetroxane (diacetone diperoxide) have been studied by gas electron diffraction and quantum chemical calculations (MP2 and B3LYP methods with 6-31G(d,p) and 6-311+G(2df,p) basis sets). The molecule possesses a chair conformation with C2h symmetry and the following geometric parameters for the six-membered ring (rh1 values) have been determined: O-O = 1.463(5) A, C-O = 1.432 (4) A, O-C-O = 108.2(7) degrees, C-O-O = 107.7(4) degrees, phi(C-O-O-C) = 63.7(4) degrees, and phi(O-O-C-O) = -63.9(4) degrees. A small contribution of less than 3.5% of a twist conformer with C2 symmetry cannot be excluded. Quantum chemical calculations predict a contribution between 1 and 2%. Additional calculations for the parent compound 1,2,4,5-tetroxane (diformaldehyde diperoxide) demonstrate that methyl substitution at the carbon atoms has a minor effect on the ring geometry but a strong effect on the conformational properties. Methyl substitution reduces the energy difference between twist and chair conformers by more than 5 kcal/mol.
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Affiliation(s)
- Sergey A Shlykov
- Department of Physics, Ivanovo State University of Chemical Technology, Engels av. 7, 153 000 Ivanovo, Russia.
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13
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Gill G, Pawar DM, Noe EA. Conformational study of cis-1,4-di-tert-butylcyclohexane by dynamic NMR spectroscopy and computational methods. Observation of chair and twist-boat conformations. J Org Chem 2006; 70:10726-31. [PMID: 16355992 DOI: 10.1021/jo051654z] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] Low-temperature 13C NMR spectra of cis-1,4-di-tert-butylcyclohexane (1) showed signals for the twist-boat (1a) and chair (1b) conformations. 13C NMR signals were assigned to specific carbons based on the different populations, different symmetries (time-averaged C(2v) for 1a and time-averaged C(s) for 1b), and calculated chemical shifts (GIAO, HF/6-311+G*). In addition to slow ring inversion and interconversion of the chair and twist-boat conformations, slow rotation of the tert-butyl groups was found. Most of the expected 13C peaks were observed. Free-energy barriers of 6.83 and 6.35 kcal/mol were found for interconversion of 1a (major) and 1b (minor) at -148.1 degrees C. Conformational space was searched with Allinger's MM3 and MM4 programs, and free energies were obtained for several low-energy conformations 1a-c. Calculations were repeated with ab initio methods up to the HF/6-311+G* level. Molecular symmetries, relative free energies, relative enthalpies and entropies, frequencies, and NMR chemical shifts were obtained. A boat conformation (1d; C(2v) symmetry) was generated and optimized as a transition state by ab initio, MM3, and MM4 calculations.
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Affiliation(s)
- Gurvinder Gill
- Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510, USA
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14
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Doherty R, Haddow MF, Harrison ZA, Orpen AG, Pringle PG, Turner A, Wingad RL. Bulky 4-phosphacyclohexanones: diastereoselective complexations, orthometallations and unprecedented [3.1.1]metallabicycles. Dalton Trans 2006:4310-20. [PMID: 16967114 DOI: 10.1039/b607490a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 4-phosphacyclohexanones, 2,2,6,6-tetramethyl-1-phenyl-4-phosphorinanone (La), 1,2,6-triphenyl-4-phosphorinanone ((Ph)Lb), 1-cyclohexyl-2,6-diphenyl-4-phosphorinanone ((Cy)Lb) and 1-tert-butyl-2,6-diphenyl-4-phosphorinanone ((Bu)Lb) have been made by modifications of literature methods. Phosphines (R)Lb are each formed as mixtures of meso- and rac-diastereoisomers. Isomerically pure rac-(Ph)Lb, rac-(Cy)Lb and meso-(Bu)Lb can be isolated by recrystallisation from MeCN. Heating mixtures of isomers of (R)Lb with TsOH leads to isomerisations to give predominantly the meso-(R)Lb. The complex trans-[PdCl2(La)2] (1) is readily made from [PdCl2(NCPh)2] but the analogous platinum complex 2 has not been detected and instead, cyclometallation at the 3-position (alpha to the ketone) in the phosphacycle occurs to give trans-[PtCl(La)(La-3H)] (3) (where La-3H = La deprotonated at the 3-position) featuring a [3.1.1]metallabicycle as confirmed by X-ray crystallography. The analogous palladabicycle 4 has been detected upon treatment of 1 with Et3N in refluxing toluene. The type of complex formed by (R)Lb depends on which diastereoisomer (meso or rac) is involved. rac-(Ph)Lb (a mixture of R,R- and S,S-enantiomers, labelled alpha and beta) forms trans-[MCl2(rac-(Ph)Lb)2], M = Pd (5) or Pt (6), as mixtures of diastereoisomers (alphaalpha/betabeta and alphabeta forms). The structure of alphaalpha-6 has been determined by X-ray crystallography. Ligand competition experiments monitored by 31P NMR showed that Pd(II) and Pt(II) have a significant preference to bind rac-(Ph)Lb over meso-(Ph)Lb. meso-(Bu)Lb reacts with [PtCl2(NCBu(t))2] under ambient conditions to give the binuclear complex [Pt2Cl2(meso-(Bu)Lb-2'H)2] (7) where orthometallation has occurred on one of the exocyclic phenyl substituents as confirmed by X-ray crystallography. rac-(Bu)Lb reacts with [PtCl2(NCBu(t))2] to give a mononuclear cyclometallated species assigned the structure trans-[PtCl(rac-(Bu)Lb-2'H)((Bu)Lb)] (8) on the basis of its 31P NMR spectrum. rac-(Cy)Lb reacts with [PtCl2(NCBu(t))2] in refluxing toluene to give trans-[PtCl2(rac-(Cy)Lb)2] (9) and the crystal structure of alphabeta-9 has been determined.
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Affiliation(s)
- Ruth Doherty
- School of Chemistry, University of Bristol, Bristol, UKBS8 1TS
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15
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Bovio B, Caramella P, Quadrelli P. Crystal structure and DFT calculations of 3,8-diphenyl-3a,4,5,5a,8a,8b-hexahydro-benzo[1,2-d: 3,4-d′]diisoxazole, C20H18N2O2. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2005.01.074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Simaan S, Biali SE. A “Classical” Tetrahydroxycalix[4]arene Adopting the 1,2-Alternate Conformation. J Org Chem 2003; 69:95-8. [PMID: 14703383 DOI: 10.1021/jo035573j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The first example of a "classical" tetrahydroxycalixarene, which adopts the 1,2-alternate conformation both in solution and in the crystal, is described. Calixarene derivatives with two distal methylene groups substituted in a trans fashion by phenyl (5a) or mesityl (5b) groups were synthesized via addition of PhMgBr/CuCN or MesMgBr/CuCN to the bis(spirodiene) derivative 3. Whereas the phenyl-substituted calixarene derivative 5a adopts the usual "cone" conformation, solution NMR data and X-ray crystallography indicate that the more crowded mesityl derivative 5b adopts a 1,2-alternate conformation with the two mesityl groups located at isoclinal positions of the macrocycle.
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Affiliation(s)
- Samah Simaan
- Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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17
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Shen Q, Traetteberg M. A reinvestigation of the molecular structure of 4,4,8,8,12,12-hexamethyltrispiro[2,1,2,1,2,1]dodecane. J Mol Struct 2003. [DOI: 10.1016/s0022-2860(03)00393-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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18
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Dinnebier R, Müller J. New insights into an old reaction. High-resolution x-ray powder diffraction of Wiberg's aminoalane intermediate. Inorg Chem 2003; 42:1204-10. [PMID: 12588158 DOI: 10.1021/ic026146b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In accordance with the procedure described by E. Wiberg, Me(3)Al-NH(3) was heated as a bulk material in inert atmosphere to give a colorless liquid which slowly loses methane. Close to the end of this elimination reaction, the melt crystallized to give a microcrystalline powder of (Me(2)AlNH(2))(x)(). The structure of this intermediate has been solved by the method of high-resolution X-ray powder diffraction. The compound crystallizes in the monoclinic space group C2/c with the cell parameters of a = 15.0047(6) A, b = 8.7500(2) A, c = 24.4702(8) A, and beta = 107.290(2) degrees, with eight trimers (Me(2)AlNH(2))(3) per unit cell. These trimers crystallize in a boat conformation in contrast to the known trimers of the same composition where a twist-boat conformation had been found by single crystal determination. Different conformers of (Me(2)AlNH(2))(3) have been investigated by theoretical methods (HF/6-31G(d), B3LYP/6-31G(d), B3LYP/6-311G(d,p), MP2(fc)/6-31G(d), and MP2(fc)/6-311G(d,p)). The twist-boat and the chair conformer correspond to minima at the potential energy surface, whereas the boat conformer corresponds to a first-order transition state (relative energies of 0.45-2.56 kJ/mol (boat) and 6.66-11.91 kJ/mol (chair)). Relaxed scans of the potential energy surface at the HF/6-31G(d) and B3LYP/6-31G(d) levels have shown that the boat conformer (C(s)() symmetry) connects two enantiomers of the twist-boat form (C(2) symmetry).
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Affiliation(s)
- Robert Dinnebier
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada
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Deschamps NM, Kaldis JH, Lock PE, Britten JF, McGlinchey MJ. Alkynylcyclohexanol chairs and twist-boats: Co(2)(CO)(6) as a conformational switch. J Org Chem 2001; 66:8585-91. [PMID: 11735541 DOI: 10.1021/jo0108820] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Treatment of 1-[axial]-(trimethylsilylethynyl)cyclohexan-1-ol with dicobalt octacarbonyl results in a conformational ring flip such that the bulky dicobalt-alkyne cluster moiety now occupies the favored equatorial site. However, when a 4-tert-butyl substituent is present, the coordinated alkynyl group retains its original axial or equatorial position. Complexation of trans-[diaxial]-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol brings about a chair-to-chair conformational inversion such that both cluster fragments now occupy equatorial sites. In contrast, cis-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol reacts with Co(2)(CO)(8) to yield the twist-boat conformer in which the two axial hydroxy substituents exhibit intra-molecular hydrogen bonding. Likewise, the corresponding reaction of cis-1,4-bis(trimethylsilylethynyl)cyclohexane-1,4-diol with Co(2)(CO)(8) leads to a twist-boat, but in this case, the molecules are linked through inter-molecular hydrogen bonds. Eight of these cobalt clusters have been characterized by X-ray crystallography, and the potential use of twist-boats in synthesis is discussed.
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Affiliation(s)
- N M Deschamps
- Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1
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Synthesis and conformational properties of several maximally substituted hexa(spirotetrahydrofuranyl)cyclohexanes. Assessment Of the pronounced bias of the all-trans D(3)(d)()-symmetric isomer for total equatorial oxygen occupancy. J Org Chem 2000; 65:9172-9. [PMID: 11149866 DOI: 10.1021/jo0014313] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The poly(spirotetrahydrofuranyl)cyclohexanes 1-4 were prepared in a series of steps that began with oxidative demercuration of pentaspirocyclic chloromercurials. Once the resulting alcohols were transformed into their ketones, it proved possible to cap this center with the Normant reagent and introduce the final heterocyclic ring. The cyclohexanones and the title compounds showed a strong tendency to project their C-O bonds equatorially to the maximum extent possible. The reluctance of these systems to participate in chair-to-chair conformational equilibration was made apparent during measurements to assess their coordination capability toward alkali metal ions. Although 3 was superior to its isomers, this polyether was overshadowed by 15 to an extent in excess of two powers of 10 in their relative capability to coordinate lithium cations. The synthesis, conformation, and low-level dynamic character of 5 are also detailed. To set the stereochemistry of the sixth spirotetrahydrofuranyl ring properly in this case, it was necessary to implement a novel strategy involving late-stage introduction of the oxygen atom. This protocol required intermediate formation of homoallylic alcohol 39, the epoxidation of which proceeded principally in the desired direction. X-ray crystallographic analysis of 5 established that the chair conformation which is adopted has all six C-O bonds projected equatorially. The total inability of 5 to bind to Li(+), Na(+), and K(+) denotes the existence of a substantial barrier to ring inversion. DNMR studies undertaken to assess the magnitude of this barrier demonstrated no change in high-field (1)H and (13)C line shapes up to 573K in 1, 3-([D(3)]methoxy)benzene. Consequently, 5 may qualify as the cyclohexane having the highest chair-chair conformational inversion barrier to the present time.
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Golan O, Cohen S, Biali SE. cis-syn-cis-1,2,4,5-Tetracyclohexylcyclohexane. A Moderately Crowded Saturated Hydrocarbon Adopting a Twist-Boat Conformation. J Org Chem 1999. [DOI: 10.1021/jo990453q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Oren Golan
- Department of Organic Chemistry, The Hebrew University of Jerusalem Jerusalem 91904, Israel
| | - Shmuel Cohen
- Department of Organic Chemistry, The Hebrew University of Jerusalem Jerusalem 91904, Israel
| | - Silvio E. Biali
- Department of Organic Chemistry, The Hebrew University of Jerusalem Jerusalem 91904, Israel
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Weiser J, Holthausen MC, Fitjer L. HUNTER: A conformational search program for acyclic to polycyclic molecules with special emphasis on stereochemistry. J Comput Chem 1997. [DOI: 10.1002/(sici)1096-987x(19970730)18:10<1264::aid-jcc2>3.0.co;2-l] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wulf K, Klages U, Rissom B, Fitjer L. STERICALLY CROWDED CYCLOHEXANES-9. [1] SYNTHESIS, CONFORMATION AND DYNAMICS OF HEXASPIRO[2.0.4.0.2.0.4.0.2.0.4.0]TETRACOSANE. Tetrahedron 1997. [DOI: 10.1016/s0040-4020(97)00289-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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