Enolate Heterocoupling: A Different Kind of Direct Functionalization A Phil S. Baran Methodology 27 October 2009 A Phil S. Baran Methodology 27 October 2009
2 1,4-Dicarbonyl Moeities Needless to say this group is omnipresent
3 How Would YOU Make This?
4 Added Complexity? Tetrahedron, 1999, 55, Bioorg. Med. Chem., 2002, 10, 2569 J. Am. Chem. Soc., 2006, 128, 2552Synlett., 2002, 1069 Org. Lett., 2001, 3, 2591 J. Am. Chem. Soc., 1998, 120, 2658
5 A More Direct Approach Historical Perspective on Enolate Coupling Origins of the Work in the Baran Group Intramolecular Enolate Heterocoupling Intermolecular Enolate Heterocoupling
6 Origins of Enolate Coupling Ivanoff, D.; Spassoff, A. Bull. Soc. Chim. Fr., 1935, 2, 76 Renaud, P.; Fox, M. A. J. Org. Chem., 1988, 53, 3745
7 A Forgotten Reaction Re-Discovered Kauffmann, T.; Beissner, G.; Berg, H.; Köppelmann, E.; Legler, J.; Schönfelder, M. Angew. Chem. Int. Ed. Engl., 1968, 7, 540 Rathke, M. W.; Lindert, A. J. Am. Chem. Soc., 1971, 93, 4605 Yields are starting to be synthetically useful Limited to homocoupling
8 How About Some Heterocoupling? Saegusa, T. et al. J. Am. Chem. Soc. 1975, 97, 2912 and J. Am. Chem. Soc. 1977, 99, 1487
9 How About Some Heterocoupling? Tokuda, M.; Shigei, T.; Itoh, M. Chem. Lett., 1975, 621 Reaction once again forgotten for 30 years Still room for improvement Yields moderate and excess reagents required For more comprehensive summary see: Baran, P. S. et al. J. Am. Chem. Soc., 2007, 129, Baran, P. S. et al. J. Am. Chem. Soc., 2008, 130,
10 Phil Baran Date of Birth: 10 Aug Simultaneous high school graduation from Mt. Dora High School and A.A. degree with honors from Lake Sumter Community College, Florida B.S. with Honors in Chemistry, New York University Advisor: Professor D.I. Schuster Ph.D. graduate student in Chemistry, The Scripps Research Institute Advisor: Professor K.C. Nicolaou Postdoctoral Associate, Harvard University Advisor: Professor E.J. Corey - 83 Papers and 4 Patents (30-40 undergrad thru post-doc) - Awards: Sackler Prize, 2009 NationalFresenius Award,ACS, 2007 Novartis Lecturer, 2007 – 2008 Hirata Gold Medal, 2007 Pfizer Award for Creativity in Organic Synthesis, 2006 Beckman Foundation Fellow, 2006 – 2008 Alfred P. Sloan Foundation Fellow, 2006 – 2008 BMS Unrestricted “Freedom to Discover” Grant, 2006 – 2010 NSFCAREERAward, 2006 – 2010 Eli Lilly Young Investigator Award, 2005 – 2006 AstraZeneca Excellence in Chemistry Award, 2005 DuPont Young Professor Award,2005 Roche Excellence in Chemistry Award, 2005 Amgen Young Investigator Award, 2005 Searle Scholar Award, 2005 GlaxoSmithKline Chemistry Scholar Award, 2005 – 2006 Nobel Laureate Signature Award in Chemistry, ACS, 2003 National Institutes of Health Post-Doctoral Fellowship Award, Harvard, 2001 – 2003 Hoffmann-La Roche Award for Excellence in Organic Chemistry, 2000 Lesly Starr Shelton Award for Excellence in Chemistry Graduate Studies, Scripps, 2000 National Science Foundation Pre-Doctoral Research Fellowship Award, Scripps, 1998 – 2001 William and Sharon Bauce Family Foundation Fellowship Award, Scripps, 1997 Dean’ s Undergraduate Research Fund Award in Chemistry, NYU,1996 – 1997 George Granger Brown Award for Excellence in Chemistry, NYU, 1996 – 1997 NYU College of Art and Sciences Scholarship, 1995 – 1997 Herman and Margaret Sokol Chemistry Fellowship, NYU, 1995 – 1997
11 Let’s Start with Indoles Baran, P. S.; Richter J. M. J. Am. Chem. Soc. 2004, 126, 7450 Disconnection places a positive charge on a negative site Clearly not an enolate but NB!! Direct Approach!! Vaillancourt, V.; Albizati, K. F. J. Am. Chem. Soc. 1993, 115, 3499
12 Direct Enolate Coupling with Indoles Baran, P. S.; Richter J. M. J. Am. Chem. Soc. 2004, 126, 7450 “Isolated as colorless cubes” “Can perform the reaction on 100 mmol scale without diminished yields”
13 Selected Scope of the Reaction Baran, P. S.; Richter J. M. J. Am. Chem. Soc. 2004, 126, 7450 Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129,
14 Application to Natural Products Baran, P. S.; Richter J. M. J. Am. Chem. Soc. 2004, 126, 7450 Baran, P. S.; Richter J. M. J. Am. Chem. Soc. 2005, 127, Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129, 12857
15 A Different Heterocycle.... Sort of Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615
16 Coupling of Pyrroles Towards (S)-Ketorolac Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Frazier, R. H.; Harlow, R. L. J. Org. Chem. 1980, 45, 5408 How does the reaction work?
17 Mechanism of Indole and Pyrrole Coupling Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129, ρ = -0.61
18 Mechanism of Indole and Pyrrole Coupling Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129, 12857
19 Mechanism of Indole and Pyrrole Coupling Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129, Other observations: Dimerization of the indole is not observed, unless the ketone is not present or cannot be oxidized N-protections kills the reaction Ferrocenium does not promote inter- molecular reaction, and Cu does not promote intramolecular Jahn, U.; Harmann, P. Chem. Commun. 1998, 209 Jahn, U.; Harmann, P. J. Chem. Soc. Perkin Trans , 2277
20 Mechanism of Indole and Pyrrole Coupling Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Baran, P. S., et al. J. Am. Chem. Soc. 2007, 129, 12857
21 Mechanism of Indole and Pyrrole Coupling Baran, P. S.; Richter J. M.; Lin, D. W. Angew. Chem. 2005, 117, 615 Proposed radical but not ‘free’ radical They do not really propose anything
22 Lessons Learned Can get ‘heterocoupling’ if both reagents are not equivalent Ketones, amides, esters tolerated Mechanism is radicalar and tunable Need ~1.5 equiv oxidant relative to more reactive partner
23 Towards Heteroenolate Coupling Baran, P. S.; Guerrero, C. A.; Hafensteiner, B. D.; Ambhaikar, N. B. Angew. Chem. Int. Ed. 2005, 44, 3892 Baran, P. S.; Guerrero, C. A.; Ambhaikar, N. B.; Hafensteiner, B. D. Angew. Chem. Int. Ed. 2005, 44, 606 Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero, C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678
24 Intramolecular Heteroenolate Coupling Baran, P. S.; Guerrero, C. A.; Hafensteiner, B. D.; Ambhaikar, N. B. Angew. Chem. Int. Ed. 2005, 44, 3892 Baran, P. S.; Guerrero, C. A.; Ambhaikar, N. B.; Hafensteiner, B. D. Angew. Chem. Int. Ed. 2005, 44, 606 Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero, C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678 Now they had a model system
25 Intramolecular Heteroenolate Coupling Baran, P. S.; Guerrero, C. A.; Hafensteiner, B. D.; Ambhaikar, N. B. Angew. Chem. Int. Ed. 2005, 44, 3892 Baran, P. S.; Guerrero, C. A.; Ambhaikar, N. B.; Hafensteiner, B. D. Angew. Chem. Int. Ed. 2005, 44, 606 Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero, C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678
26 Intramolecular Heteroenolate Coupling Baran, P. S.; Guerrero, C. A.; Hafensteiner, B. D.; Ambhaikar, N. B. Angew. Chem. Int. Ed. 2005, 44, 3892 Baran, P. S.; Guerrero, C. A.; Ambhaikar, N. B.; Hafensteiner, B. D. Angew. Chem. Int. Ed. 2005, 44, 606 Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero, C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678 This product is the precursor to the others
27 Intramolecular Heteroenolate Coupling Baran, P. S.; Guerrero, C. A.; Hafensteiner, B. D.; Ambhaikar, N. B. Angew. Chem. Int. Ed. 2005, 44, 3892 Baran, P. S.; Guerrero, C. A.; Ambhaikar, N. B.; Hafensteiner, B. D. Angew. Chem. Int. Ed. 2005, 44, 606 Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero, C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678 Proposed models
28Recap
29Optimization Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
30 Selected Scope with Iron Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
31 Selected Scope with Iron Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
32 Selected Scope with Copper Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
33Applications Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
34 Mechanistic Studies - Evidence for Radicals Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, SET Test Yang, D.; et al. Tetrahedron: Asymmetry 2003, 12, 2927 Suggests that single electron transfer is likely
35 Mechanistic Studies - Evidence for Radicals Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, Homodimerization Test Radical Transfer Test
36 Mechanistic Studies - Evidence for Radicals Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, ρ = -0.63
37 Mechanistic Studies - Evidence for Radicals Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, ρ = -0.25
38 Transition-State Models - Evan’s Oxazolidinone Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, Suggests that model for each system is different Proposed models based on metal loadings
39 Transition-State Models - Effects of M Loading Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, Adjusted Yield based on Oxidant Stoichiometry
40 Transition-State Models - Iron Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
41 Transition-State Models - Copper Baran, P. S.; DeMartino, M. P. Angew. Chem. Int. Ed. 2006, 45, 7083 DeMartino, M. P.; Chen, K.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 11546
42Conclusions Versatile, scalable, cheap, powerful method Simplifies access to 1,4-dicarbonyl compounds even if yields are moderate Tolerant of complex functionality Will undoubtedly be used in industry Some limitations / work to do (WIP?) Quartenary centres difficult to access dr’s are quite low Rely on ‘dated’ auxilliary chemistry Can have only 1 enolizable center per partner Versatile, scalable, cheap, powerful method Simplifies access to 1,4-dicarbonyl compounds even if yields are moderate Tolerant of complex functionality Will undoubtedly be used in industry Some limitations / work to do (WIP?) Quartenary centres difficult to access dr’s are quite low Rely on ‘dated’ auxilliary chemistry Can have only 1 enolizable center per partner
43 HAPPY HALLOWEEN!!!!