Leon J. Tilley

Leon J. Tilley

Professor of Chemistry

ltilley@stonehill.edu
508-565-1145
Shields 314
Chemistry

Biography

Professor Tilley joined the chemistry department in 1996 after completing his Ph.D. from Indiana University. He earned B. A.'s in Chemistry and Russian Language from Grinnell College in 1990.

His Ph.D. research involved conductometric rate-constant, isotope effect, and NMR product studies of gamma- and delta-silyl substituted carbocations, as well as software design for a bipolar pulsed conductance instrument. He also spent the summer of 2000 as an Adjunct Assistant Professor at Northeastern University and the summer of 2001 as a Visiting Investigator at the Woods Hole Oceanographic Institute. He is actively engaged in undergraduate research at Stonehill College, and has had numerous undergraduate research students working with him on a variety of projects, funded by a variety of external and internal grants, including the SURE program.

He also teaches a variety of courses ranging from General Chemistry with a forensic theme to Organic Chemistry to Inorganic Chemistry. He is also interested in mineralogy and is an avid mineral collector.

Education

  • Ph.D. Indiana University, Bloomington, IN, 1996
  • B.A. Chemistry, B. A. Russian Language, Grinnell College, 1990

Research Interests

  • Synthesis of electron-withdrawing substituted strained ring systems via gamma silyl-elimination
  • Synthesis of novel oxoammonium salts and nitroxyl radicals 
  • New methods for the oxidation of trifluoromethyl alcohols
  • Improved methods for conjugate addition of silyl groups
  • Improved methods for fluoroalkyl group addition to carbonyl compounds
  • Synthesis of a number of small polyhedral systems including tetrahedrane and octaazadodecahedrane derivatives
  • Mechanistic studies of gamma-silyl-bridged carbocations
  • Synthetic applications of silyl-bridged systems

Courses Taught

  • Organic Chemistry I
  • Organic Chemistry II
  • General Chemistry I 
  • Inorganic Chemistry
  • Advanced Topics in Inorganic Chemistry

We have several ongoing projects in two principal areas: 1) The application of gamma-silyl bridging toward the synthesis of strained hydrocarbon systems, and 2) The synthesis of novel oxoammonium ions and nitroxyl radicals and their potential application as green oxidants for oxidation of trifluoromethyl alcohols and other systems.  We are also developing novel synthetic methodologies in order to further our research in both of these areas.

Carbocations containing a gamma-silyl substitutent are known to be stabilized by a bridging, or "percaudal" interaction in which the back-lobe of the silicon-carbon bond overlaps with the developing carbocation p-orbital. Subsequent elimination (one possible pathway) of the gamma-silyl substituent leads to formation of a new (1, 3) bond.  We have found that carbocations destabilized by highly-electron-withdrawing groups (EWGs) in the position alpha to a leaving group undergo strong percaudal participation and almost exclusively follow the 1,3-elimination pathway.   We have taken advantage of this mechanism to form a variety of EWG-substituted cyclopropanes, as well as even more-highly strained EWG-substituted bicyclobutanes. We are currently exploring the scope of EWGs capable of directing this reaction.  Synthesis of the substrates for these reactions is also necessitating developing improved methodologies for precursor-reactions including conjugate addition of silyl groups and fluoroalkylation reactions of carbonyl compounds. 

Our gamma-silyl elimination methodology has potential applications for synthesis of bicyclic systems that could serve as novel bioisosteres in pharmaceutical applications. We are also exploring the possibility of applying gamma-silyl elimination to synthesize even more highly strained systems such as tetrahedranes.  Such strained systems have potential applications as high-energy-density materials/fuels.

Our other project involves the development of novel oxoammonium salts and nitroxyl radicals.  4-(acetylamino)-2,2,6,6-tetramethyl-1-oxo-piperidinium tetrafluoroborate, otherwise known as “Bobbitt’s salt,” is a heavy-metal-free, recyclable oxidant capable of undergoing a variety of oxidations, including oxidation of alcohols to aldehydes and ketones.  We are currently exploring the synthesis and characterization of modified versions of this system.  We are also interested in the nitroxyl precursors of these modified oxoammonium salts.  Nitroxyl radicals (also known as nitroxides) are unusual, stable radical species and themselves are also useful as oxidants (often catalytically in the presence of a co-ocidant) and also as biochemical spin-labels.

We are currently preparing and studying the electronic properties and oxidizing abilities of these modified compounds.  They have potential use for oxidation of trifluoromethyl alcohols to the corresponding carbonyl compounds, or as unique spin-labels for probing a variety of biological systems.

 

Publications:

  • Toward a Unified Mechanism for Oxoammonium Salt-Mediated Oxidation Reactions: A Theoretical and Experimental Study Using a Hydride Transfer Model Hamlin, T. A.; Kelly, C. B.; Ovian, J. M.; Wiles, R. J.; Tilley, L. J.; Leadbeater, N. E. J. Org.Chem., 2015, 80(16), 8150-8167.
  • Synthesis of Perfluoroalkyl-Substituted Vinylcyclopropanes by Way of Enhanced Neighboring Group Participation Kelly, C. B.; Mercadante, M. A.; Carnaghan, E. R.; Doherty, M. J.; Fager, D. C.; Hauck, J. J.; MacInnis, A. E.; Tilley, L. J.; Leadbeater, N. E. Eur. J. Org. Chem., 2015, 4071–4076. 
  • 1,3-γ-Silyl Elimination in Electron-Deficient Cationic Systems Mercadante, M. A.; Kelly, C. B.; Hamlin, T. A.;  Delle Chiaie, K. R.; Drago, M. D.; Duffy, K. K.; Dumas, M. T. Fager, D. C.; Glod, B. L. C. Hansen, K. E.;  Hill, C. R.; Leising, R. M.; Lynes, C. L.; MacInnis, A. E.; McGohey, M. R.; Murray, S. A.; Piquette, M. C.; Roy, S. L.; Smith, R. M.; Sullivan, K. R.; Truong, B. H.; Vailonis, K. M.; Gorbatyuk, V.; Leadbeater, N. E.; Tilley, L. J., Chem. Sci. 2014, 5, 3893-3994.
  • Synthesis of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate and 4-acetamido-(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl and their use in oxidative reactions Mercadante, M. A.; Kelly, C. B.; Bobbitt, J. M.; Tilley, L. J.; Leadbeater, N. E. Nature Protocols 2013, 8, 666-676.
  • A revised preparation of (4-Acetamido-2,2,6,6-tetramethylpiperidin-1-yl)oxyl and 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate: reagents for stoichiometric oxidations of alcohols Tilley, L. J.; Bobbitt, J. M.; Murray, S. A.; Camire, C. E.; Eddy, N. A.  Synthesis 2013, 45, 326-329.
  • Discussion addendum for: preparation of 4-Acetylamino-2, 2, 6, 6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate and the Oxidation of geraniol to geranial (2,6-octadienal, 3,7-dimethyl-, (2e)-) Bobbitt, J. M.; Eddy, N. A.; Richardson, J. J.; Murray, S. A.; Tilley, L. J. Organic Syntheses 2013, 90, 215-228.
  • Enabling the Synthesis of Perfluoroalkyl Bicyclobutanes via 1,3 γ-Silyl Elimination Kelly, C. B.; Colthart, A. M.; Constant, B. D.; Corning, S. R.; Dubois, L. N. E.; Genovese, J. T.; Radziewicz, J. L.; Sletten, E. M.; Whitaker, K. R.; Tilley, L. J. Org. Lett. 2011, 13(7), 1646-1649.
  • Electron-deficient γ-silyl Systems:  Methods for Synthesis of 1,1,1-trifluoromethyl-4-trimethylsilyl-2-butanone Heath, D. A.; Tilley, L. J. The Nucleus 2009, 87(7), 12-15.
  • Got a Match? Ion Extraction GC–MS Characterization of Accelerants Adsorbed in Charcoal Using Negative Pressure Dynamic Headspace Concentration Tilley, L. J.; Anzivino, B.; Drugan, J. E.; Hall, A. B. Ingalls, L. R. J. Chem. Educ. 2009, 86(1), 55-60.
  • Fun with Computational Chemistry:  Solving Spectral Problems using Computed 13C NMR Chemical Shifts.  A Comparison of Empirical and Quantum Mechanical Methods Tilley, L. J.; Prevoir, S. J.; Forsyth, D. A. J. Chem. Educ. 2002, 79(5), 593-600.
  • γ-Silyl-stabilized Tertiary Ions?  Solvolysis of 4-(trimethylsilyl)-2-chloro-2-methylbutane, Tilley, L. J.; Shiner, V. J., Jr.  J. Phys. Org. Chem. 1999, 12, 564-576.

Presentations:

  • Tilley, L. J.; Leadbeater, N. E.; Kelly, C. B.; Mercadante, M. A.; Corning, S. R.; Genovese, J. T.; McGohey, M. M.; Sullivan, K. R.; Delle Chiaie, K. R.; Murray, S. A. Electron-deficient cation directed γ-silyl elimination as a tool for forming trifluoromethylcyclopropanes, 242nd ACS National Meeting & Exposition, Denver, CO, August 28-September 1, 2011.
  • Tilley, L. J. Enhancing γ-silyl Participation using Electron-deficient Carbocations:  A Method for Selective Formation of Cyclopropanes and Bicyclobutanes, University of Connecticut Chemistry Department Seminar, November 10, 2010.
  • Purisky, B.; Tilley, L. Trifluoroethoxide assisted formation of electron-withdrawing substituted bicylobutanes Presented at Undergraduate Poster Session, 257th ACS National Meeting & Exposition, Orlando, FL, March 31-April 4, 2019.
  • Rapela, V.; Tilley, L. Synthesis of electron withdrawing oxoammonium salts Presented at Undergraduate Poster Session, 257th ACS National Meeting & Exposition, Orlando, FL, March 31-April 4, 2019.
  • Giardino, G.; Tilley, L. Synthesis of pyridyl and propiolyl bicyclobutanes Presented at Undergraduate Poster Session, 255th ACS National Meeting & Exposition, New Orleans, LA, March 18-22, 2018.
  • Hickey, E.; Tilley, L. Synthesis of methoxytetrahedrane and trimethylsilylbicyclobutane Presented at Undergraduate Poster Session, 255th ACS National Meeting & Exposition, New Orleans, LA, March 18-22, 2018.
  • Giardino, G.; Tilley, L. J. Synthesis of acetylinic and pyridyl bicyclobutanes Presented at Undergraduate Poster Session, 253rd ACS National Meeting & Exposition, San Francisco, CA, April 2-6, 2017.
  • Hickey, E.; Tilley, L. J.  Synthesis of methoxytetrahedrane by coupling and elimination of dibromosilylcylcobutane Presented at Undergraduate Poster Session, 253rd ACS National Meeting & Exposition, San Francisco, CA, April 2-6, 2017.
  • Wolf, M. S.; Tilley, L. J. Synthesis of all-trans cyclobutyl systems and investigation of electron-withdrawing substituents Presented at Undergraduate Poster Session, 253rd ACS National Meeting & Exposition, San Francisco, CA, April 2-6, 2017.
  • Ovian, J.; Kelly, C. B.; Hamlin, T.; Lambert, K. M.; Loman, J.; Mercadante, M. A.; Bailey, W. F.; Tilley, L. J.; Leadbeater, N. E. Oxoammonium salts: Powerful yet practical reagents for oxidation and oxidative functionalization in chemistry Presented at 252nd ACS National Meeting & Exposition, Philadelphia, PA, August 21-25, 2016.
  • Hunt, A.; Tilley, L. J. Nitro as an electron-withdrawing group to enhance gamma-silyl elimination for the production of bicyclobutane derivatives Presented at Undergraduate Poster Session 251st ACS National Meeting & Exposition, San Diego, CA, March 13-17, 2016.
  • Johnston, S.; Tilley, L. J. Optimization and exploration of four-membered ring formation Presented at Undergraduate Poster Session 251st ACS National Meeting & Exposition, San Diego, CA, March 13-17, 2016.
  • Macary, L.; Tilley, L. J. Effects of steric bulk on silyl bridging in the synthesis of trifluoromethylbicyclobutane Presented at Undergraduate Poster Session 251st ACS National Meeting & Exposition, San Diego, CA, March 13-17, 2016.
  • Poto, M. ; Tilley, L. J. Synthesis of cyanobicyclobutane via the gamma silyl effect Presented at Undergraduate Poster Session 251st ACS National Meeting & Exposition, San Diego, CA, March 13-17, 2016.
  • Wolf, M.; Tilley, L. J. Synthesis of all-trans cyclobutyl systems Presented at Undergraduate Poster Session 251st ACS National Meeting & Exposition, San Diego, CA, March 13-17, 2016.
  • Macary, L.; Hauck, J.; Tilley, L. J. Investigating the effects of steric bulk on γ-silyl bridging by varation of the γ-electron-donating and α-substituent Presented at Undergraduate Poster Session 249th ACS National Meeting & Exposition, Denver, CO, March 22-26, 2015.
  • MacInnis, A. E.; Tilley, L. J.; Leadbeater, N. E.; Carnaghan, E. R.; Doherty, M.; Fager, D. C.; Hauck, J.; Kelly, C. B.; Mercadante, M. A.; Accessing vinyl fluoroalkyl-substituted cyclopropanes from homoallyl mesylates via a destabilized cation mediated electron cascade Presented at Undergraduate Poster Session 249th ACS National Meeting & Exposition, Denver, CO, March 22-26, 2015.
  • Summer 2020 “α-Perfluoroalkyl Nitroxyls and Their Oxoammonium Salts: Accessing More Powerful TEMPO Oxidants” Organic Syntheses Undergraduate Summer Research Award. 
  • Summer 2019 “Investigation of Alkoxide Initiators for Difluoromethylation reactions” National Science Foundation (NSF) Scholarships in Science, Technology, Engineering, and Mathematics Program (S-STEM) to research student Nwanne Banor for summer research.
  • 2019 “Optimization of TMSLi Conjugate Addition using TPPO as a safer alternative to HMPA” Norris-Richards Undergraduate Summer Research Scholarships sponsored by the Northeastern Section of the American Chemical Society (NESACS).
  • 2008-2009, 2011-2014 “Investigation of Silyl Eliminations of Cyclobutyl and Bicyclobutyl Systems as Potential New Routes to Tetrahedrane and Strained Hydrocarbon Fuels for Solid-Oxide Fuel Cells (SOFCs)” Office of Naval Research Grant.
  • Summer 2018 “Synthesis of Pyridyl and Propiolyl Bicyclobutanes” Stonehill Undergraduate Research Experience (SURE) grant with student Gavin Giardino.
  • Summer 2018 “Synthesis of Methoxytetrahedrane and Trimethylsilylbicyclobutane” Stonehill Undergraduate Research Experience (SURE) grant with student Erin Hickey.
  • Summer 2018 “Synthesis of Difluorobicyclobutane” Stonehill Undergraduate Research Experience (SURE) grant with student Samuel Perreault.
  • Summer 2018 “Synthesis of Electron Withdrawing Oxammonium Salts” Stonehill Undergraduate Research Experience (SURE) grant with student Victoria Rapela.
  • Summer 2018 Stonehill College Chemistry Department CURE (Chemistry Undergraduate Research Experience) grant to support summer research for student Hannah Mackay.
  • Summer 2017 “Synthesis of Acetylenic and Pyridyl Bicyclobutanes” Stonehill Undergraduate Research Experience (SURE) grant with student Gavin Giardino.
  • Summer 2017 “Synthesis of Methoxytetrahedrane and 1,4-addition to 4-TMS-cyclobutenone” Stonehill Undergraduate Research Experience (SURE) grant with student Erin Hickey.
  • Summer 2017 Martha’s Vineyard Vision Fellowship (funding for student Erin Hickey and materials for project).
  • Summer 2016 “Enhancing the Oxidizing Power of Bobbitt’s Salt” Stonehill Undergraduate Research Experience (SURE) grant with student Samuel Johnston.
  • Summer 2016 “Bicyclobutyl Bridging en Route to Synthesis of Tetrahedrane” Stonehill Undergraduate Research Experience (SURE) grant with student Anthony Moriondo.
  • Summer 2015 “Investigation of Electron-withdrawing Substituents in the Synthesis of Cyclopropanes, Bicyclobutanes, and Tetrahedranes” Stonehill Undergraduate Research Experience (SURE) grants with student Andrew Hunt. 
  • Summer 2015 “Synthesis and bridging of cyclobutyl systems toward preparation of strained ring systems” Lloyd G. Balfour Foundation Stonehill College-Massasoit Community College Science Transfer Initiative grant for one S-STEM transfer student, Samuel Johnston, and one Stonehill student mentor, Margaret Wolf.

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