Transcript Palladium (II)/Palladium (IV) catalytic processes : new

Palladium (II)/Palladium (IV)
catalytic processes : new options to
consider for C―H bonds activation.
A literature review on Melanie S.
Sanford’s recent work.
Presented by Guillaume Pelletier.
Outline of the presentation.
• Introduction to the concept of C-H bond activation
Industrial processes
Interesting recent work in this field
Applications in total synthesis
• Oxidative C-H bond functionalization using PhI(OAc)2 and
Pd(OAc)2.
Crabtree et al. work in the 1990’s.
Melanie S. Sanford’s work using benzo[h]quinoline
Interesting mechanistic work on the Pd(II)/Pd(IV) catalytic cycle
Application of the Pd(II)/Pd(IV) concept to related and different
systems.
Formation of C-C bonds : mechanistic insights
Formation of C-X bonds
Synthesis of cyclopropanes through enynes cyclisation
Aminooxygenation of alkenes.
Why C-H bonds are powerful tools to access to
diversification of organic molecules?
• Among the most abundant bonds…
• …but also the least reactive bonds.
• Could be a powerfull tool to convert a common
bond into a linear alcohol, amines or α-olefins.
• Direct conversion of a « unfunctionalized » bond
(no oxidation/protection needed).
A quick overview on the “C-H activation” in a
simple industrial process.
2 CH4 + 4 H2SO4-Pd(II)  CH3CO2H + 4 SO4 + 6H2O
Complimentary to the Mosento
process
10% Overall Yield (could be
improved by adding MeOH or
CO)
Harsh conditions used
Periana, R. A.; Taube, D. J.; Gamble, S.; Taube, H.; Satoh, T.; Fujii, H. Science, 1998, 280, 560.
A more complex problematic : Applications of C-H
bond functionalisation in total synthesis.
Bore, L.; Honda, T.; Gribble, G. W. J. Org. Chem. 2000, 65, 6278-6282.
A more complex problematic : Applications of C-H
bond functionalisation in total synthesis.
Johnson, J. A.; Li, N.; Sames, D. J. Am. Chem. Soc. 2002, 124, 6900-6903.
What were the major problematics to C―H bond
functionalisation before 1990’s…
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Usually there is low level of regiochemistry.
Harsh conditions are often used.
Low TON
Low functional group tolerance
Significant formation of byproducts
Large excess of substrate/oxidant/catalyst loading are
typically required.
• In summary, there is an open space to a lot of groups to
circumvent any of these factors and to propose a more
efficient transformation.
Classification of the reactions with two
different concepts.
Dick, A. R.; Sanford, M. S. Tetrahedron 2006, 62, 2439-2463.
Some pionnier work on efficient C―H bond
activation/transformation.
Chen, H.; Schlech, S.; Semple, C. T.; Hartwig, J. F. Science, 2000, 287, 1995-1997.
Some pionnier work on efficient C―H bond
activation/transformation.
A lot of additive were screened. TfOH promoted the reaction. (26 to
91 % Yields)
A large elctronic dependance over the substrates (kobs(OMe) ~
kobs(H)>>kobs(CF3))
Slow C-H bond activation (kH/kD = 3.5)
Boele, M. D. K.; Strijdonck, G. P. F. V.; De Vries, A. H. M.; Kamer, P. C. J.; De Vries, J. G.; Leeuwen, P. W. N. M. V.
J. Am. Chem. Soc. 2002, 124, 1586-1587.
Some pionnier work on efficient C―H bond
activation/transformation.
An
efficient
methodology
to
form
1,3difunctionalized amines through a selective C─H
bond oxidation.
The sulfamate ester is forming a nitrene-metal
intermediate with the rhodium.
Espino, C. G.; When, P. M.; Chow, J.; Du Bois. J. J. Am. Chem. Soc. 2001, 123, 6935.
Formation of C-O bonds by using a more friendly
oxidant : PhI(OAc)2
Stock et al. reported earlier that Cr2O7- anion did promoted the
oxidation of PhPd(OAc) species.
Eberson et al. proposed previously to use peroxydisulfate as the
oxidant.
Stock, L. M.; Tse, I. J.; Walstrum, S. A. J. Org. Chem. 1981, 46, 1757-1761.
Eberson, L.; Jönsson, L. Acta Chem. Scand. B. 1976, 30, 361-364.
Kinetics of the reaction.
• He found that PhPd(II)OAc
intermediate fails to form the
carbon-heteroatom bond.
The most important fact to remember is that C-O bond is only formed
on oxidation, presumably via a reductive elimination from a
PhPd(IV)OAc species.
Yoneyama, T.; Crabtree, R. H. J. Mol. Cat. A: Chem. 1996, 108, 35-40.
Kinetics of the reaction and mechanism.
• He found that k(H)/k(D) ~4.3 (C-H activation step is rate limiting).
Yoneyama, T.; Crabtree, R. H. J. Mol. Cat. A: Chem. 1996, 108, 35-40.
Some of Crabtree’s conclusions
• Considering the regioslectivity of the acetoxylation of anisole (o:m:p
= 44:5:51) the C-H insertion step is rather an electrophilic attack by
the Pd (o:m:p ~ 60:0:30) than a oxidative addition/reductive
elemination pathway (o:m:p = 12:76:12).
• Sigma bond methathesis may be considered.
• PhI(OAc)2 is a more selective and smooth oxidant than Cr2O7-.
• PhI(OAc)2 favors the formation of C-O bonds from C-H bonds and
not C-C homocoupling.
Yoneyama, T.; Crabtree, R. H. J. Mol. Cat. A: Chem. 1996, 108, 35-40.
About 10 years later…
Dick, A. R.; Hull, K.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300-2301.
Hartwell, G. E.; Lawrence, R. V.; Smas, M. J. J. Chem. Soc. Chem. Commun.
1970, 912.
Melanie S. Sanford
• She received her undergraduate degree in
chemistry from Yale University in 1996 where she
worked with Professor Robert Crabtree studying CF bond functionalization.
• She then moved to Caltech where she worked with
Professor Robert Grubbs investigating the
mechanism of ruthenium-catalyzed olefin
metathesis reactions.
• After receiving her PhD in 2001, she worked with
Professor Jay Groves at Princeton University as an
NIH post-doctoral fellow studying
metalloporphyrin-catalyzed functionalization of
olefins.
• Melanie has been a professor at the University of
Michigan since the summer of 2003.
Her first paper about a Pd(II)/Pd(IV) oxidative
functionalization of C-H bonds.
• Very good yields were obtained
without exclusion of
air/moisture
• She showed that the reaction
tolerates variety of X = OAc,
OMe, Br, Cl, OEt.
• 2.5 equiv. PhI(OAc)2 gives the
doubly acetylated products
Dick, A. R.; Hull, K.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300-2301.
Proposed catalytic cycle
Using the cyclopalladated benzo[h]quinoline catalyst in the reaction
without the oxidant does not form the product.
Dick, A. R.; Hull, K.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300-2301.
Precedents on the C-X bond formation in a similar
mechanism.
Han, R. Y.; Hillhouse, G. L. J. Am. Chem. Soc. 1997, 119, 8135-8137
Williams, B. S.; Goldberg, K. I. J. Am. Chem. Soc. 2001, 123, 2576-2578
Application of the concept to an sp3 carbon C-H
bond.
No β-hydroelimination product was observed due to Palladacycle
rigidity.
Desai, V. L.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 9542-9543
High selectivity obtained at the ortho position.
Kalyani, D.; Sanford, M. S. Org. Lett. 2005, 7, 4149-4172.
An important observation : the selectivity of the
reaction…
Desai, V. L.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 9542-9543
Other important observations…
Oxidative cleavage of the C-O bond and C-H activation step are both
highly stereoselective
Desai, V. L.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 9542-9543
Does Pd(IV) exist?
Yamamoto, Y.; Kuwabara, S.; Matsuo, S.; Ohno, T.; Nishiyama, H.; Itoh, K. Organometallics, 2004, 23, 3898-3903.
Canty, A. J.; Patel, J.; Rodemann, T.; Ryan, J. H. Skelton, B.W.; White, A. H. Organometallics, 2004, 23, 3466-3469.
Does Pd(IV) exist?
Càmpora, J.; Palma, P.; Del Rio, D.; Carmona, E.; Graiff, G.; Tiripiccio, A. Organometallics, 2003, 22, 3345-3349.
To study the system, Pt(IV) is more
suitable…
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
Pt(II) is like Pd(II)…
Huang, T. S.; Chen, J. T.; Lee, G. H.; Wang, Y. Organometallics, 1991, 10, 175-180.
Design of new Pt(III) and Pt(IV) complexes
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
Platinum (III) complex
Treatment of this complex
with 10 PhI(OAc)2 does not
over oxidize it.
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
Platinum (IV) complex synthesis
With benzo[h] quinoline, with R = OMe, the ratio A:B is 2:1 and
with R = OiPr A:B = 0.4:1.
Stable (purified by chromatography)
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
Platinum (IV) synthesis
C-N ligand =
Benzo[h]quinoline
ROH = MeOH
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
Various tests with the 8-Methylquinoline
We see the same trend that the one observed with the palladium complex.
When R is big for ROH, the ratio of product with 8-methylquinoline is less
interesting than the one observed with small R group
Dick, A. R.; Kampf, J. W.; Sanford, S. M. Organometallics, 2005, 24, 482-485.
New Pd (IV) catalysts isolation
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
New Pd (IV) X-Ray
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
Reductive elimination step pathways
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
Reductive elimination step pathways: first
approach.
• If mechanism A is the right one, then there should be a radical solvent effect on
the speed rate of the reaction.
BUT!!
In polar acetone : ε = 21, krel = 1.0 ± 0.1
In apolar solvent : ε = 2.3 krel = 1.0 ± 0.1
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
Willams, B. S.; Goldberg, K. I. J. Am. Chem. Soc. 2001, 123, 2576-2578.
Reductive elimination step pathways: Erying
studies.
• Erying studies gives a
value of +4.2 ± 0.4 and
-1.4 ± 1.9 in DMSO and
CDCl3 for ∆S†.
• Typically, we see a
value of -13 to -49 for
C-C and C-Se reductive
elimination with Pd(IV)
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
Canty, A. J.; Jin, H.; Skelton, B. W.; White, A. H. Inorg. Chem. 1998, 37, 3975-3978.
Hammet studies with various X substituents.
• Benzoate acts as a
nucleophilic partner in the
transformation (σ = -1.36 ±
0.04)
• σ value of -1.5 with C-S
coupling with Pd(II) which
goes through a Mechanism
type B
• σ value of + 1.44 for
reductive elimination from
Pt(IV) (stabilization of the
–OR moiety).
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
Reductive elimination step pathways : crossover
reactions.
• With these observations, mechanism A can be ruled out.
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
How to dicriminate between B and C?
• Mechanism B and C are kinetically indistinguishable…
Dick, A. R.; Kampf, J. W.; Sanford, S. M. J. Am. Chem. Soc. 2005, 127, 12790-12791.
How can we push further the concept?
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Possible mechanisms
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Possible mechanisms
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Important results
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Important results
• With these observations, mechanisms C and D can be ruled out.
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Important results
Hull, K. L.; Lanni, E. L.; Sanford, M. S. J. Am. Chem. Soc. 2006, 128, 14047-14049.
Other methodologies: C-F bond formation.
Hull, K. L.; Anani, Q. W.; Sanford, M. S. J. Am. Chem. Soc. 2007, 128, 7134-7135.
Other methodologies: C-Cl, C-Br and C-I bond
formation.
Kalyani, D.; Dick, A. R.; Anani, W. Q.; Sanford, M. S. Org. Lett. 2006, 8, 2523-2526.
Other methodologies: C-Cl, C-Br and C-I bond
formation.
Whitfield, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142-15143.c
Synthesis of cyclopropanes through enynes
cyclisation
Welbes, L. L.; Lyons, T. W.; Cychosz, K. A.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 5838-5839.
Aminooxygenation of alkenes.
Desai, L. V.; Sanford, M. S. Angew. Chem. Int. Ed. 2007, 46, 5737-5740.
And today…ASAP JACS
Yu, W. Y.; Sit,W. N.; Lai, K. M.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. ASAP
Conclusion
• Pd(II)/Pd(IV) can be applied to various catalytic
systems to form interesting products (such as new
C-O, C-C and C-X bond formation).
• Isolation of a variety of stable , purifiable and
temperature resistant Pd(IV) catalysts.
• Various kinetic and crossover studies were done to
elucidate the different mechanisms.
• Diversification of pyridine derivatives via a directed
C-H bond activation/diversification concept.