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Hansen T, Vermeeren P, Zijderveld KWJ, Bickelhaupt FM, Hamlin TA. S N 2 versus E2 Competition of Cyclic Ethers. Chemistry 2023; 29:e202301308. [PMID: 37338310 DOI: 10.1002/chem.202301308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/20/2023] [Accepted: 06/20/2023] [Indexed: 06/21/2023]
Abstract
We have quantum chemically studied the influence of ring strain on the competition between the two mechanistically different SN 2 and E2 pathways using a series of archetypal ethers as substrate in combination with a diverse set of Lewis bases (F- , Cl- , Br- , HO- , H3 CO- , HS- , H3 CS- ), using relativistic density functional theory at ZORA-OLYP/QZ4P. The ring strain in the substrate is systematically increased on going from a model acyclic ether to a 6- to 5- to 4- to 3-membered ether ring. We have found that the activation energy of the SN 2 pathway sharply decreases when the ring strain of the system is increased, thus on going from large to small cyclic ethers, the SN 2 reactivity increases. In contrast, the activation energy of the E2 pathway generally rises along this same series, that is, from large to small cyclic ethers. The opposing reactivity trends induce a mechanistic switch in the preferred reaction pathway for strong Lewis bases from E2, for large cyclic substrates, to SN 2, for small cyclic substrates. Weak Lewis bases are unable to overcome the higher intrinsic distortivity of the E2 pathway and, therefore, always favor the less distortive SN 2 reaction.
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Affiliation(s)
- Thomas Hansen
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - Pascal Vermeeren
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - Kim W J Zijderveld
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
| | - F Matthias Bickelhaupt
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
- Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen (The, Netherlands
- Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
| | - Trevor A Hamlin
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) Vrije Universiteit, Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam (The, Netherlands
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Hansen T, Roozee JC, Bickelhaupt FM, Hamlin TA. How Solvation Influences the S N2 versus E2 Competition. J Org Chem 2021; 87:1805-1813. [PMID: 34932346 PMCID: PMC8822482 DOI: 10.1021/acs.joc.1c02354] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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We have quantum chemically
investigated how solvation influences
the competition between the SN2 and E2 pathways of the
model F– + C2H5Cl reaction.
The system is solvated in a stepwise manner by going from the gas
phase, then via microsolvation of one to three explicit solvent molecules,
then last to bulk solvation using relativistic density functional
theory at (COSMO)-ZORA-OLYP/QZ4P. We explain how and why the mechanistic
pathway of the system shifts from E2 in the gas phase to SN2 upon strong solvation of the Lewis base (i.e., nucleophile/protophile).
The E2 pathway is preferred under weak solvation of the system by
dichloromethane, whereas a switch in reactivity from E2 to SN2 is observed under strong solvation by water. Our activation strain
and Kohn–Sham molecular orbital analyses reveal that solvation
of the Lewis base has a significant impact on the strength of the
Lewis base. We show how strong solvation furnishes a weaker Lewis
base that is unable to overcome the high characteristic distortivity
associated with the E2 pathway, and thus the SN2 pathway
becomes viable.
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Affiliation(s)
- Thomas Hansen
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Jasper C Roozee
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - F Matthias Bickelhaupt
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.,Institute for Molecules and Materials (IMM), Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Trevor A Hamlin
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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Eden BD, Rice AJ, Lovett TD, Toner OM, Geissler EP, Bowman WE, Young SC. Microwave-assisted synthesis and in vitro stability of N-benzylamide non-steroidal anti-inflammatory drug conjugates for CNS delivery. Bioorg Med Chem Lett 2019; 29:1487-1491. [PMID: 30987893 DOI: 10.1016/j.bmcl.2019.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 03/27/2019] [Accepted: 04/08/2019] [Indexed: 02/05/2023]
Abstract
More effective delivery of non-steroidal anti-inflammatory drugs (NSAIDs) to the brain could treat the underlying inflammatory pathology of a range of CNS diseases and conditions. Use of a blood-brain barrier shuttle such as the N-benzylamide moiety, which has been largely unexplored for this purpose, could improve the brain bioavailabilities of NSAIDs. A series of novel N-benzylamide NSAID conjugates was synthesized via a three-step process with a microwave-assisted bimolecular nucleophilic substitution as the final step. We explored conditions to promote substitution over a competing elimination reaction, which was successfully suppressed with isopropyl alcohol solvent. All molecules exhibit physicochemical properties consistent with those of brain-penetrant molecules. Furthermore, they exhibit long (>48 h) half-lives in phosphate-buffered saline (PBS; pH 7.4) and short to moderate half-lives in human plasma. N-Benzylamide NSAID conjugates represent promising CNS drug discovery leads.
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Affiliation(s)
- Brandon D Eden
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - Andrew J Rice
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - Troy D Lovett
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - Olivia M Toner
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - Evan P Geissler
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - William E Bowman
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States
| | - Sherri C Young
- Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, PA 18104, United States.
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Satpathy L, Sahu PK, Behera PK, Mishra BK. Solvent Effect on the Potential Energy Surfaces of the F - + CH 3CH 2Br Reaction. J Phys Chem A 2018; 122:5861-5869. [PMID: 29909618 DOI: 10.1021/acs.jpca.8b02687] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although substantial work has been undertaken on reaction pathways involved in base-promoted elimination reactions and bimolecular nucleophilic substitution reaction of F- on CH3CH2X (X = Cl, Br, I), the effect of solvents with varying dielectric constants on the stereochemistry of each of the reaction species involved across the reaction profile have not yet been clearly understood. The present investigation reports the effect of solvents on the potential energy surfaces (PES) and structures of the species appearing in the reaction pathway of F- with bromoethane. The PESs in the gas phase have been computed at MP2 level and CCSD(T) level. The performance of several hybrid density functional, such as B3LYP, M06, M06L, BHandH, X3LYP, M05, M05-2X, and M06-2X have also been investigated toward describing the elimination and nucleophilic substitution reactions. With respect to MAE values and to make the computation cost-effective, we have explored the implicit continuum solvent model, CPCM in solvents like cyclohexane, methanol, acetonitrile, dimethyl sulfoxide and water. The reactant complexes proceed through the subsequent steps to produce fluoroethane as the substitution product and ethylene as one of the elimination products. For elimination reaction both syn and anti elimination have been explored. The calculated relatives energies values, which are negative in the gas phase, are found to be positive in polar solvents since the point charge in the separated reactants are more stabilized than the dispersed charge in the transient complex, which has also been analyzed through NBO analysis.
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Affiliation(s)
- Lopamudra Satpathy
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
| | - Prabhat K Sahu
- Computational Modeling Research Laboratory , School of Chemistry Sambalpur University , Jyoti Vihar 768 019 , India
| | - Pradipta K Behera
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
| | - Bijay K Mishra
- Centre of Studies in Surface Science and Technology, School of Chemistry , Sambalpur University , Jyoti Vihar 768 019 , India
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Stewart MN, Hockley BG, Scott PJH. Green approaches to late-stage fluorination: radiosyntheses of 18F-labelled radiopharmaceuticals in ethanol and water. Chem Commun (Camb) 2015; 51:14805-8. [DOI: 10.1039/c5cc05919d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Green strategies for late-stage fluorination with 18F, in which ethanol and water are the only solvents used throughout the entire radiolabeling process, have been developed and applied to the radiosyntheses of a range of radiopharmaceuticals commonly employed in clinical PET imaging.
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Affiliation(s)
- Megan N. Stewart
- Department of Medicinal Chemistry
- College of Pharmacy
- The University of Michigan
- Ann Arbor
- USA
| | - Brian G. Hockley
- Division of Nuclear Medicine
- Department of Radiology
- The University of Michigan Medical School
- Ann Arbor
- USA
| | - Peter J. H. Scott
- Department of Medicinal Chemistry
- College of Pharmacy
- The University of Michigan
- Ann Arbor
- USA
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Shao X, Schnau PL, Fawaz M, Scott PJH. Enhanced radiosyntheses of [¹¹C]raclopride and [¹¹C]DASB using ethanolic loop chemistry. Nucl Med Biol 2013; 40:109-16. [PMID: 23123138 PMCID: PMC3514660 DOI: 10.1016/j.nucmedbio.2012.09.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 09/25/2012] [Accepted: 09/28/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION To improve the synthesis and quality control of carbon-11 labeled radiopharmaceuticals, we report the fully automated loop syntheses of [¹¹C]raclopride and [¹¹C]DASB using ethanol as the only organic solvent for synthesis module cleaning, carbon-11 methylation, HPLC purification, and reformulation. METHODS Ethanolic loop chemistry is fully automated using a GE TRACERLab FX(C-Pro) synthesis module, and is readily adaptable to any other carbon-11 synthesis apparatus. Precursors (1 mg) were dissolved in ethanol (100 μL) and loaded into the HPLC loop. [¹¹C]MeOTf was passed through the HPLC loop and then the labeled products were purified by semi-preparative HPLC and reformulated into ethanolic saline. RESULTS Both [¹¹C]raclopride (3.7% RCY; >95% RCP; SA=20831 Ci/mmol; n=64) and [¹¹C]DASB, both with (3.0% RCY; >95% RCP; SA=15152Ci/mmol; n=9) and without (3.0% RCY; >95% RCP; SA=10931 Ci/mmol; n=3) sodium ascorbate, have been successfully prepared using the described methodology. Doses are suitable for human use and the described methods are now employed for routine clinical production of both radiopharmaceuticals at the University of Michigan. CONCLUSIONS Ethanolic loop chemistry is a powerful technique for preparing [¹¹C]raclopride and [¹¹C]DASB, and we are in the process of adapting it for other carbon-11 radiopharmaceuticals prepared in our laboratories ([¹¹C]PMP, [¹¹C]PBR28 etc.).
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Affiliation(s)
- Xia Shao
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Paul L. Schnau
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Maria Fawaz
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Peter J. H. Scott
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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