C-H Functionalization: Recent Applications Jean-Francois Vincent-Rocan Department of Chemistry University of Ottawa Organic and Biological Chemistry Graduate seminar April 12, 2012 1 Books and Reviews 2 C-H Functionalization in SciFinder 500 450 400 Publication per year 350 300 250 200 150 100 50 0 1981 1987 1992 1997 2002 2007 -Constant growth in the past 30 years -Explosion in the last 5 years -Focus on recent applications (not a comprehensive review) 3 Activation vs Functionalization • C-H bond activation: Cleavage of C-H bond that leads to the formation of a metal-C bond either through oxidative addition to a low valent metal center or electrophilic substitution • C-H bond functionalization: Cleavage of C-H bond that is followed by new bond formation at the carbon center Shilov, A. E.; Shul'pin, G. B. Chem. Rev. 1997, 57, 2879-2932 Kaikuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345, 1077-1101 4 Outline • Part 1: Factors of selectivity – Inductive effects – Hyperconjugation – Steric factors – Strain release – Directed oxidations • Part 2: Recent applications – Mimicking nature – Increasing molecular complexity – Cross-Coupling – Divergent functionalization in drug discovery 5 Part 1 Factors of selectivity 6 C-H Oxidation Mechanism using Dioxiranes 7 Curci Acc. Chem. Res. 2006, 39, 1 Bond Strengths -Stronger bonds are formed -Most electron rich C-H is the easiest to break 8 Inductive Effects -The most electron rich position is oxidized for non-metal insertions -Typical reactivity trend is tertiary> secondary> primary -Secondary positions are less sterically hindered Selectivity can be tuned by reagent selection (polyoxometalates) Asensio, G.; Castellano, G.; Mello, R.; Gonzalez-Nunez, M. E. J. Org. Chem. 1996, 61, 5564−5566 Kamata, K.; Yonehara , K.; Nakagawa, Y.; Uehara, K.; Mizuno, N. Nat. Chem. 2010, 2, 478 – 483 Hyperconjugation Effects -Cyclopropane act as activating group (oxidation on the vicinal carbon) -Orbital overlap is required Daccolti, L.; Dinoi, A.; Fusco, C.; Russo, A.; Curci, R. J. Org. Chem. 2003, 68,7806 – 7810 Banwell, M. G.; Haddad, N.; Huglin, J. A.; MacKay, M. F.; Reum, M. E.; Ryan, J. H.; Turner, K. A. J. Chem. Soc. Chem. Commun.1993, 954 – 957 Brinker, U.H.; Lin, G.; Xu, L.; Smith, W. B.; Mieusset, J.-L. J. Org. Chem. 2007, 72, 8434 – 8451. 10 Hyperconjugation Enabled by Heteroatoms -Non-bonding electrons of a heteroatom available for hyperconjugation - Non-bonding electron MUST be available (Delocalization in the aromatic ring in this case) Davies, H. M. L.; Beckwith, R. E. J.; Antoulinakis, E. G.; Jin, Q. J. Org. Chem. 2003, 68, 6126 – 6132. Barton, D. H. R.; Boivin, J.; Gaudin, D.; Jankowski, K. Tetrahedron Lett. 1989, 30, 1381 – 1382. Liang, C.; Fabien, C.; Fruit, C.; Mller, P.; Dodd, R. H.; Dauban, P. Angew. Chem Int. Ed. 2006, 45, 4641 – 4644. 11 Steric Factors -Rate reduction for hindered C-H bonds -Hyperconjugation + steric factors R= TMS TES TBS TIPS TBDPS Rel. Rate 102 39 14 1,7 1 Tenaglia, A.; Terranova, E.; Waegell, B. Tetrahedron Lett. 1989, 30, 5271 – 5274 Davies, H. M. L.; Venkataramani, C. Angew. Chem. Int. Ed. 2002, 41, 2197 – 2199 Gomez, L.; Garcia-Bosch, I.; Company, A.; Benet-Buchholz, J.; Polo, A.; Sala, X.; Ribas, X.; Costas, M. Angew. Chem. Int. Ed. 2009, 48, 5720 – 5723. Davies, H. M. L.; Beckwith, R. E. J.; E. Antoulinakis, G.; Jin, Q. J. Org. Chem. 2003, 68, 6126 – 6132. 12 Strain Release - Elimination of 1,3 syn diaxial interaction in the transition state promotes a faster oxidation and an increased site-selectivity (in the example below) - Schreiber and Eschenmoser proposed this idea for the oxidation of axial alcohols (1955) . Chen, K.; Eschenmoser, A.; Baran, P.S. Angew. Chem. Int. Ed. 2009, 48, 9705 – 9708 Schreiber, J.; Eschenmoser, A. Helv. Chim. Acta 1955, 38, 1529 –1536 13 Energy diagram 14 Directed Oxidations -Excellent in the presence of opposing steric and electronic influences -Directing group is overriding the substrate’s preferences Breslow, R.; Corcoran, R. J.; Snider, B. B.; Doll, R. J.; Khanna, P. L.; Kaleya, R. J. Am. Chem. Soc. 1977, 99, 905 – 915 Kasuya, S.; Kamijo, S. ; Inoue, M. Org. Lett. 2009, 11, 3630 – 3632. 15 How is it Selective ? 16 Directing Groups Override Substrate Preferences -Directing groups can be employed to reverse the inherent selectivity -Intramolecular delivery is more important than the steric effects of the substrate Chen, K.; Richter, J. M.; Baran, P. S. J. Am. Chem. Soc. 2008, 130, 7247 – 7249 Hofmann, A. W. Ber. Dtsch Chem. Ges. 1879, 12 (1): 984–990 Löffler, K.; Freytag, C. Ber. Dtsch Chem. Ges. 1909, 42 (3): 3427–3431 17 Radical[1,6]-Hydrogen Shift HLF reaction 18 Metal Promoted Directed Oxidation Espino, C. G.; When, P. M.; Chow, J.; Du Bois, J. J. Am. Chem. Soc. 2001, 123, 6935 – 6936 Yu, J.-Q.; Giri, R.; Chen, X. Org. Biomol. Chem. 2006, 4, 4041 – 4047 19 Directed Pd C-H activation • Insertion via CIPE, to form the new C-Pd bond 20 Chen, X.; Engle, K. M.; Yu, J.-Q. Angew. Chem. Int. Ed., 2009, 48, 5094-5115 Hydrogen Bonding -Competitive ketone formation on the second substrate -H-bonding with TFDO is impossible for the second example 21 Asensio, G.; Gonzlez-Nfflez, M. L.; Bernardini, C. B.; Mello, R.; Adam, W. J. Am. Chem. Soc. 1993, 115, 7250 – 7253 First Part: Conclusion • Inductive effects, hyperconjugation, steric factors and strain release will modulate C-H selectivity • Directed oxidation can be use for selective oxidation of complicated system or to invert the selectivity 22 Part 2: Recent Applications 23 Late Stage Hydroxylation • C-H activation can be used to avoid PGchemistry using late-stage hydroxylation Wender, P. A.; Hilinski, M. K.; Mayweg, A. V. W. Org. Lett. 2005, 7, 79– 82 Seto, H.; Fujioka, S.; Koshino, H.; Yoshida, S. ; Tsubuki, M.; Honda, T. Tetrahedron 1999, 55, 8341 – 8352 Curci, R.; Detomaso, A.; Prencipe, T.; Carpenter, G. B. J. Am. Chem. Soc. 1994, 116, 8112−8115 24 Mimicking Nature • Nature usually oxidizes the targeted compound at the end of its biosynthesis • An abundant number of natural products are synthesised in 2 phases : Cyclase phase and Oxidation phase 25 Chen, K.; Baran, P. S. Nature 2009, 459, 824–828 Baran’s Retrosynthetic Analysis for the Eudesmane Terpenes Family 26 Chen, K.; Baran, P. S. Nature 2009, 459, 824–828 Eudesmanes Synthesis: Cyclase Phase 27 Chen, K.; Baran, P. S. Nature 2009, 459, 824–828 Eudesmanes synthesis: Oxidation phase 28 Chen, K.; Baran, P. S. Nature 2009, 459, 824–828 Eudesmanes synthesis: Oxidation phase 29 Chen, K.; Baran, P. S. Nature 2009, 459, 824–828 C-H functionalization • Aliphatic C-H (inherent preference, Directed oxidation) 30 The White Group • • • Major player in the allylic C-H functionalization field Known for her Palladium(II) \ sulfoxide catalyst system for allylic oxidation π-allyl complex followed by functionaliztion Chen, M.S.; White, M.C. J. Am. Chem. Soc 2004, 126, 1346-1347 Fraunhoffer, K.J.; White, M.C. J. Am. Chem. Soc 2007, 129, 7274-7276 Reed, S. A.; Mazzotti, A. R.; White, M. C. J. Am. Chem.Soc. 2009, 131, 11701-11706 Young, A. J.; White, M. C. Angew. Chem., Int. Ed. 2011, 50, 6824-6827 31 Increasing Molecular Complexity -Stang and White developed that method to take fairly simple S.M and converted it to reactive intermediate 32 Stang, E. M.; White, M. C. J. Am. Chem. Soc. 2011, 133, 14892-14895 Optimization Entry 1 Catalyst Solvent Pd(OAc)2 dioxane Additive Dienophile Yield diene % Yield cycloadduct % - - 1 - 2 1 dioxane - - 6 - 3 2 dioxane - - 28 - 4 2 dioxane - NPM 1 33 5 2 DCE - NPM 1 52 6 2 DCE p-NO2BzOH NPM 1 74 7 2 DCE p-NO2BzOH - 35 33 Stang, E. M.; White, M. C. J. Am. Chem. Soc. 2011, 133, 14892-14895 Reaction Scope 34 Stang, E. M.; White, M. C. J. Am. Chem. Soc. 2011, 133, 14892-14895 Application in synthesis 35 Stang, E. M.; White, M. C. J. Am. Chem. Soc. 2011, 133, 14892-14895 C-H functionalization • Aliphatic C-H (inherent preference, Directed oxidation) • Allylic C-H (Directed, allyl activation) 36 Cross-Coupling reactions • Reaction using organohalides and pseudohalides and other functional groups • The reactive intermediate is the corresponding aryl and alkyl palladium(II) species. • The quickest and easiest sequences to prepare such intermediates would certainly improve these reactions • Unlimited opportunities for the use of unactivated carbon– hydrogen (C-H) bond 37 Chen, X.; Engle, K. M.; Yu, J.-Q. Angew. Chem. Int. Ed., 2009, 48, 5094-5115 Cross-Coupling Featuring C-H Functionalization Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496-16497 Giry, R.; Maugel, N.; Li, J. J.; Wang, D. H.; Breazzano, S. P.; Saunders, L. B.; Yu, J. Q. J. Am. Chem. Soc. 2007, 129, 3510– 3511 Satoh, T.; Kawamura, Y.; Miura, M.; Nomura , M. Angew. Chem. Int. Ed. Engl. 1997, 36, 1740 Kamer, P. C. J.; de Vries, J. G.;Van Leeuwen , P.W. N. M .J. Am. Chem. Soc. 2002, 124, 1586 38 Concerted Metalation Deprotonation 39 Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496-16497 Oxidative Heck Cross-Coupling Beck, E. M.; Grimster, N. P.; Hatley, R. ; Gaunt, M. J. J. Am. Chem. Soc. 2006, 128, 2528 40 Application in Total Synthesis 41 Beck, E. M.; Hatley, R.; Gaunt, M. J. Angew. Chem., Int. Ed. 2008, 47, 3004-3007 Late-Stage Functionalization - 9 membered ring - Late stage functionalization - Functional group ‘’tolerance’’ 42 Bowie, A. L.; Hughes, C. C.; Trauner, D. Org. Lett. 2005, 7, 5207-5209 Cross-coupling featuring C-H functionalization Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496-16497 Giry, R.; Maugel, N.; Li, J. J.; Wang, D. H.; Breazzano, S. P.; Saunders, L. B.; Yu, J. Q. J. Am. Chem. Soc. 2007, 129, 3510– 3511 Satoh, T.; Kawamura, Y.; Miura, M.; Nomura , M. Angew. Chem. Int. Ed. Engl. 1997, 36, 1740 Kamer, P. C. J.; de Vries, J. G.;Van Leeuwen , P.W. N. M .J. Am. Chem. Soc. 2002, 124, 1586 43 Directing group 44 For a good review :Chen, X.; Engle, K. M.; Yu, J.-Q. Angew. Chem. Int. Ed., 2009, 48, 5094-5115 Drug Discovery • Sulfonamide is an organic moiety present in many drugs • Has been found to direct C-H functionalization 45 Dai, H.-X.; Stepan, A. F.; Plummer, M. S.; Zhang, Y.-H.; Yu, J.-Q. J. Am. Chem. Soc. 2011, 133, 7222-7228 Divergent Functionalization 46 Dai, H.-X.; Stepan, A. F.; Plummer, M. S.; Zhang, Y.-H.; Yu, J.-Q. J. Am. Chem. Soc. 2011, 133, 7222-7228 Drug Analogues 47 Dai, H.-X.; Stepan, A. F.; Plummer, M. S.; Zhang, Y.-H.; Yu, J.-Q. J. Am. Chem. Soc. 2011, 133, 7222-7228 C-H functionalization • Aromatic C-H (inherent preference, protecting group orientation, directing group) 48 Conclusion – 4 factors have been identified to modulate C-H functionalization selectivity (inductive effects, hyperconjugation, steric factors, strain release) – Directed oxidations can overcome the substrate’s preferences – C-H functionalization can be used easily in total synthesis of complex and drug-like molecules 49 What Is Next ? 50 Mendoza, A.; Ishihara, Y.; Baran, P.S. Nature Chem. 2012, 4, 21-25. Acknowledgements Dr. André Beauchemin Francis Loiseau Melissa Macdonald Christian Clavette Amanda Bongers Nicolas Guimond Tom Markiewicz Keira Garland Bashir Hussain Colin Hesp Valérie Lemieux Pierre Mouawad Patrick Moon Nicolas Das Neves Wei Gan Shu-Bin Zhao 51 Question 52