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Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N- Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated.

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Presentation on theme: "Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N- Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated."— Presentation transcript:

1 Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the N- Heterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters Article by Karl A. Scheidt. Angewandte Chemie. 2011, 50, Review by Benjamin Roembke, Department of Chemistry and Biochemistry, University of Maryland, College Park 20740

2 Karl A. Scheidt B.S.: University of Notre Dame 1994 Ph.D: Indiana University 1999 Research Statement: “Our research focuses on two complementary areas: the discovery of new organic reactions and bioorganic chemistry. We are particularly interested in designing novel methods and strategies for the construction of complex natural products with important biological attributes. Our methodology programs encompass assembling molecules and introducing stereogenic centers using new catalytic reactions.” Faculty profiles, Northwestern University:

3 Goal of the Study  Use enals and -unsaturated -ketoesters to form highly substituted cyclopentanes Karl A. Scheidt. Angewandte Chemie. 2011, 50,

4 Carbene Catalysts  Used in organic chemistry to cause polarity reversal also know as Umpolung.  Umpolung is the German name for ‘inverse polarity’. It is given to synthons with d 1, a 2, d 3, a 4 … reactivity. Clayden, J.; Greeves, N.; Warren S.; Wothers, P. Organic Chemistry, 1 st ed.; Oxford University Press: New York, 2001; pp

5 Synthons Clayden, J.; Greeves, N.; Warren S.; Wothers, P. Organic Chemistry, 1 st ed.; Oxford University Press: New York, 2001; pp

6 Homoenolates: An Umpolung synthon  In this study, an enal is converted into a homoenolate by reaction with a carbene catalyst  Homoenolate (d 3 synthon) is a compound containing an anionic carbon  to a carbonyl or a moeity that can be transformed into a carbonyl V. Nair, S. Vellalath, B. P. Babu. Chem. Soc. Rev. 2008, 37, 2691

7 Discovery of the Homoenolate Ion  Proof of the homoenolate ion  Optical activity was reduced to zero A. Nickon and J. L. Lambert. J. Am. Chem. Soc., 1962, 84, 4604

8 Early Example of Homoenolate Equivalents Used in C-C formation  Silyl ethers in the form of cyclopropyl ketals were used as homoenolate equivalents  TiCl 4 problematic E. Nakamura and I. Kuwajima, J. Am. Chem. Soc., 1977, 99, 7360

9 Reaction of Enals and Chalcones V. Nair, S. Vellalath, M. Poonoth, E. Suresh. J. Am. Chem. Soc. 2006, 128, 8736

10 Proposed Catalytic Cycle V. Nair, S. Vellalath, M. Poonoth, E. Suresh. J. Am. Chem. Soc. 2006, 128, 8736

11 Optimization Reaction Karl A. Scheidt. Angewandte Chemie. 2011, 50,

12 Varying  -Subtitution on the Ketoester Karl A. Scheidt. Angewandte Chemie. 2011, 50,

13 Varying Substitution of the Enal Karl A. Scheidt. Angewandte Chemie. 2011, 50,

14 Catalytic Cycle Karl A. Scheidt. Angewandte Chemie. 2011, 50,

15 Synthetic Utility of Products Karl A. Scheidt. Angewandte Chemie. 2011, 50,

16 Acknowledgements  Dr. Davis  The class


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