Department of Chemistry

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Ted Cohen

Professor Emeritus

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1206 CHVRN

Chevron Science Center 219 Parkman Avenue


Pittsburgh, PA 15260
412-624-8220

Research Overview

Development of New Synthetic Methods and Mechanistic Organic Chemistry

Our synthetic mode involves: (1) the design of new chemical reactions often based on our mechanistic studies; (2) sequencing these so as to produce new synthetic methodology; (3) the application of the latter to particularly novel and efficient syntheses of natural products.

The discovery that aromatic radical-anions can reductively cleave C-S bonds has led to some of the most versatile methods known for producing carbanions for synthetic purposes, including the simplest and most general procedures for producing α-lithioethers, α-lithiosilanes, cyclohexenyl- and cycloheptenyllithiums, homoallyllithiums, and allyllithiums.  In the latter case, considerable regiochemical and stereochemical control can be exerted.  One use of these allyllithiums is in the Li-ene cyclization, eventually leading to our study of the analogous Zn-ene cyclization, resulting in perhaps the most efficient synthesis of (-)-kainic acid 1 (see below); an improved procedure that avoids the partial racemization occurring in one of the steps is being developed.

The use of a δ-lithiooxyanion in the most efficient synthesis from commercially available materials of the bee pheromone 2 in its natural pure enantiomeric state is shown.

bee pheromone 2

Awards

Ramsay Memorial Fellow (Great Britain), 1955-56

Chancellor's Distinguished Research Award, University of Pittsburgh, 1992

The Pittsburgh Award, Pittsburgh Section, American Chemical Society, 2009.

Publications

“Synthesis of (-)-α-Kainic Acid via TMSCl-Promoted Pd-Catalyzed Zinc-ene Cyclization of an Allyl Acetate,” Wei, G.; Chalker, J. M.; Cohen, T., J. Org. Chem., Vol. 76, 2011, Pages 7912-7917
“Readily Prepared 3-Chloro-1-(phenylthio)propene, A Versatile Three-Carbon Annulating Agent,” Liu, T.; Zhao, X.; Lu, L.; Cohen T., Org. Lett., Vol. 11, 2009, Pages 4576-4579
“Enantio- and Diastereoselective Tandem Zn-Promoted Brook Rearrangement/Ene-Allene Carbocyclization Reaction,” Marek, I; Cohen, T.; Chinkov, N.; Stanger, A.; Unger, R.; Weisser, F., Org. Lett., Vol. 11, 2009, Pages 1853-1856
“Enantioselective Ring Expansion of Prolinols. An Efficient and Short Synthesis of 2-Phenylpiperidin-3-ol Derivatives and 3-Hydroxypipecolic Acids,” Cochi, A.; Burger, B.; Navarro, C.; Pardo, D. G.; Cossy, J.; Zhao, Y.; Cohen, T., Synlett, 2009, Pages 2157-2161
“Two Syntheses of (–)‑Kainic Acid via Highly Stereoselective Zinc‑ene Cyclizations,” Chalker, J.; Yang, A.; Deng, K.; Cohen, T., Org. Lett., Vol. 9, 2007, Pages 3825-3828
“Intramolecular Carbozincation of Unactivated Alkenes Occurs Through a Zinc Radical Transfer Mechanism,” Cohen, T.; Gibney, H.; Ivanov, R.; Yeh, E. A.-H.; Marek, I.; Curran, D. P., J. Am. Chem. Soc., Vol. 129, 2007, Pages 15405-15409