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Enjoin wolff-kishner reduction
1. An Old Dog with New Tricks:
Enjoin Wolff–Kishner Reduction for
Alcohol Deoxygenation and C–C Bond Formations
Presented By:
Stephin Baby
Dept. Of Medicinal Chemistry
MC/2019/21
2. THE PRESENTATION INCLUDES:
Introduction
1
History and
emergence of
Wolff-Kishner
reduction
2 Transitions in
Development3
Evolution and
exploration of
Wolff-Kishner
reduction
4 Conclusion
5 Reference
6
2/21/2020 2
3. INTRODUCTION
The Wolff-Kishner reduction
Nikolai Matveevich Kizhner (1867 – 1935) and Ludwig Wolff (1856 – 1919)
Carbonyl deoxygenation,subsequently developed two unprecedented new types of
chemical transformations:
a) alcohol deoxygenation
b) C–C bond formations
Grignard-type reaction
Conjugate addition
Olefination
Diverse cross-coupling reactions.
2/21/2020
3
4. HISTORY AND EMERGENCE
Kizhner, Professor of Organic Chemistry at the Imperial Tomsk Technological Institute, in
Siberia(1912).Published his report in the Zhurnal Russkogo Fiziko-Khimicheskogo
Obshchestva [Journal of the Russian Physical-Chemical Society]
Wolff, working at the Chemical Institute of Jena University, published a variant of the
same reaction in Justus Liebigs Annalen der Chemie(1912)
The reaction became known as the Wolff reduction until January 10, 1913, when Wolff
acknowledged Kizhner’s priority for the discovery.
In the first disclosure, Kizhner reported the Four deoxygenations.
2/21/2020 4
6. Fig 2: Wolff’s first report of a semicarbazone decomposition
The first reaction reported by Wolff was the conversion of the quinone
monosemicarbazone into the phenol
Ironically, the paper was entitled, “Method for replacing the oxygen atom of ketones and
aldehydes by hydrogen. [First paper.]” No second paper appeared.
Wolff describes that the inspiration for his discovery was an observation by Johannes
Thiele and his student, Willy Barlow.
2/21/2020 6
7. Wolff modified his procedure after obtained sufficient evidence for the involvement of a hydrazone intermediate
Fig 3: Wolff’s decomposition of semicarbazones by base.
Kishners
exploration
Wolff exploration
Camphor(28%) Benzophenone(90%)
Fenchone(28%) Acetophenone(80%)
α-ionone p-Anisaldehyde(66%)
β-ionone Vanillin(67%)
pseudoionone dibenzyl ketone
Furfural(70%) P-aminoacetophenone
carone Micheler’s ketone
Menthone(89%) 2-Hexanone
isothujone
2/21/2020
7
9. Scope and Limitation of the reaction
Scope
The synthesis of the
corticosteroids and sex hormones
Systematic synthesis of
pyrroles(Hans fischer 1929)
Structure elucidations of the
pentacyclic triterpenes(Leopold
Ruzicka 1939)
Wharton reaction
Eschenmoser-Tanabe
fragmentation
C-C bond formations
Grignard-type reactions
Conjugate additions
Transition-metal-catalyzed cross
coupling reactions
Suzuki coupling
Kumada–Corriu coupling
Stille coupling
Hiyama coupling
Negishi coupling
Sonogashira coupling.
2/21/2020 9
10. • Azine formation
• Hydrazone hydrolysis to
alcohols(Eisenlohr and Polenske)
• Required higher temperature for
the reduction proceed to
completion(180 deg.cel)
• Relatively low yields(Fenchone
and camphor)
• Decomposition of the hydrazones
to the alkene
• Time taken for completion of
reaction is more
• Dehalogenation in heterocyclic
compounds
Limitation.
Scope and Limitation of the reaction
2/21/2020 10
12. Mechanistic investigations
THE IONIC MECHANISM
Azo tautomer of the hydrazone
Reacts with hydroxide anion to
give its conjugate base
Loses molecular nitrogen to give the
carbanion
Protonated by the water molecule
Alkane
H. Harry
Szmant(1952)
2/21/2020 12
13. Fig 4: The mechanism and reaction
energy profile for the base-promoted
decomposition of cyclohexanone
hydrazone.
2/21/2020 13
14. Free-radical mechanism
Nitrogen gas & alkane
Azo compound
intermediate
React with a radical to generate
a new carbon radical
Fig 5: A putative free radical mechanism for the Wolff-Kishner reduction2/21/2020 14
15. Which one of the two, predominates???.............
Free radical
Ionic mechanism
Azo tautomer
Free radicals undergo coupling
instead of hydrogen atom
abstraction when the concentration
of hydrazine is low
N-alkylhydrazone as substrate
Hydrogen atom abstraction from
hydrazine when the concentration
of hydrazine is high
2/21/2020 15
16. Modern adaptations of the Wolff-Kishner reduction
Challenge 1
Strongly basic conditions and high
temperatures of the reaction.
Challenge 2
steric hindrance
high concentration of hydrazine
Challenge 3
Hydrolysis by water and subsequent
formation Azo derivatives
Removal of water(distillation) from the reaction
medium and use of anhydrous
01
02
03
Challenges Variation of reaction from primary observation
Relatively unencumbered ketones
2/21/2020 16
17. The Huang-Minlon modification
The first major advance in this reaction was discovered by Professor Huang-
Minlon (or Huang Ming-Long, 1898–1979)
Solvent Base Reaction time
estimated
Ketone to
Hydrazine
ratio
Yield
Soffer and
coworkers(1945)
Diethylene (b.p. 244 °C)
or triethylene
glycol (b.p. 285 °C)
triethanolamine (bp. 335
°C)
Conjugate base of
the solvent as the
base
“
Longer time is
required
“
Usually 1:10
Lower ratio
Good
Poor yield
Whitmore and his
students(1945)
High boiling alcohols
(Acid catalyst)
“ Short time was
required
1:2 Good
2/21/2020 17
18. Fig:6 The first Huang-Minlon modification of the Wolff-Kishner reduction
Outcome
Ease of use and its generally higher yields
2/21/2020 18
19. Bergmann and Orchin(1949)
Bartlett and
Knox(1939)
Sargent(1957)
Gates(1950)Rapoport(1960)
Zhilkibaev(2007)
Determination of the stereochemistry of the
Rauwolfia indole alkaloid, rauwolscine
Pelletier(1954)
3-Ethylacridine has been obtained by reduction of 3-
acetylacridine,reduction of 3-acetyl-9,10 dihydroacridine
thienyl ketones, as well
aldehydes
The reduction of the keto-
lactam to the lactam
Fieser(1948)
Stenhagen(1949)
Non-conjugated unsaturated linear keto-
esters and keto-amides to the straight-chain
carboxylic acid derivatives.
Cason(1949)
G.M. Badger(1948)
Branched-chain ketoacids(β,β-
Dialkyl-γ-ketoesters)
synthesis of the geometric
isomers of hexahydrochrysene
from the diketones
Preparation of the bornane-1-
carboxylic acid by reduction of the
2-bornanone-1-carboxylic acid
Synthesis of cyclobutane
from cyclobutanone
structural and stereochemical studies of the
diterpenes of Agathis australis
Fluorene-1-carboxylic acid from
reduction of the keto-acid
Enzell and Thomas(1965)
Roberts and Sauer(1949) Buu-Ho(1953)
Reduction of the geissoschizine
aldehyde to the methyl compound
His proofs of structure and
stereochemistry(veratrine)
The reduction of 3-aryl-2-azabicyclo[4.4.0]-decan-5-
ones gave good yields of the perhydroisoquinolines
Chatterjee and Prakash(1954)
Long-chain linear keto-acids to
the straight-chain carboxylic acids
2/21/2020 19
20. Nucleophile
used
Solvent Base Yield and Reaction
time
Temperat
ure
Outcome
Moffett and
Hunter
(1951)
anhydrous
hydrazine
Anhydrous
alcohol(methanol)
Anhydrous
alkoxide bases
Na-methoxide
11-ketosteroids-
63-82%
12h
200oC Reduction of
streically hindered
11-ketosteroids
The Barton
modification
(1955)
Anhydrous
hydrazine
Anhydrous
diethylene glycol
Sodium
alkoxide
(conjugate
base)
Hindered
diterpene dione -
69-70%
18-24h
180-
240oC
Reduction of
streically hindered
diterpene dione
The Nagata
modification
(1964)
Hydrazine
dihydrochloride
(Acid catalyzed)
Glycols(Diethylene
glycol or triethylene
glycol)
KOH 3-epi-11-oxo-
ticogenin &
Hindered imines-
90%
200oC Hindered carbonyls
and masked
carbonyl groups,
such as imines
Henbest
modification
(1963)
Hydrazine
semicarbazide
toluene
“
Potassium
tert-butoxide
“
piperidinylpinacolo
ne -83%
4-cholestene –Low
yield
Higher yield
<120oC
“
Lower
temperatures
reductive
elimination of α-
aminoketones
Further modifications………
2/21/2020 20
21. Nucleophile
used
Solvent Base Yield and Reaction
time
Temperat
ure
Outcome
The Cram
modification
(1962)
Hydrazine dimethyl sulfoxide
Potassium
tert-butoxide
Diphenyl ketone-
90%
Cyclohexanone-
80%
RT Reduction at room
temperature
Fig 7:The generation of an alkyldiazene by reduction of a hydrazone carrying a leaving group.
What about not using a base at all ?........
2/21/2020 21
22. Diazene
P-toluenesulfonylhydrazone
• A complex metal hydride(reducing
agent & Base)
• Protic solvents
• NaBH4 or LiAlH4
• Milder Reaction conditions
• Yield is good
• Two steps
• Carried out under conditions of
low pH
• Mixed DMF-sulfolane solvent
• Higher temperatures
• Sodium
cyanoborohydride(Reducing
agent)
• DMF can act as the
deprotonating base
• Higher yields & Single step
Caglioti Modification Hutchins Modification
The Caglioti & Hutchins modification(1964-1967)
2/21/2020 22
23. Synthetic Toolbox
Natural products and & Lead compounds
Desired biological Properties
Largely unexploited
Fossil-based
C feedstocks
‘Un-functionalized’
Selective
Functionalisation
To build up complexity
biomass-based
feedstocks
‘Overfunctionalized’
Selective
Defunctionalisation
by maintaining
complexity
Synthetic Mainstream
2/21/2020 23
25. Unsolved Challenge >>>>
Direct Deoxygentation with High selectivity and efficiency ????.......
One Step Deoxygenation Historical Pathway
I. Benzylic alcohol
II. Allylic alcohol
III. 1,2-dihydroxy compounds
2/21/2020 25
26. One step Methodolgy
Total Synthesis of
Sesquiterpene(Sesquicarene)
Pyridine-SO3 Complex in THF
Sulfate monoester-
intermediate(LiAlH4)0-3oC
C12H12Ti(Benzene titanium)
Deoxygenation and C-C bond
formation
THF is used(quench free
radical)
Allyl alcohol(Trans/cis)
Hydroalumination(Allyl
alcohol&Ethers
LiAlH4 in Zr
compounds(Cp2ZrCl2,ZrCl2)
Also done by Ti compounds
Tungsten Cmplex
Activate C-O bond
WH2Cl2(PMe3)4
Deoxygenate non-
allylic alcohols
Β-cyclodextrin promoted
No cis product
Terminal olefins will be
formed(RT)
E.J Corey(1969)
Henry ledon (1979)
Fumie sato(1980)
Jong-Tae Lee (1990)
Thomas J.crevies(1997)
2/21/2020 26
28. Catalysts used:
Iridium(Ir)
Ruthenium(Ru)
Manganese(Mn)
Substrate scope:
Primary alcohol(Secondary cyclicalcohols >>>>> Steric Hindrance)
Benzylic alcohol>>>ortho-methoxybenzyl alcohol(Low yield)>>>>>Strong
chelation
Allylic alcohol>>> carbon–carbon double bond (C=C) and the hydroxy group
were simultaneously reduced2/21/2020 28
29. A: Initial formation of the active species
B: Alcohol generated complex
C: β-H elimination
D: Regeneration of catalyst
Proposed Mechanism
2/21/2020 29
31. Short Summary
Efficient mainly with benzylic &
allylic alcohol
Harsh conditions
Highly concentrated
solution(10M)>>Scale up
Stoichiometric innocuous
byproducts
Practical reaction
conditions
Synthetically benign
Single step with High
selectivity on 1o alcohols
Great functional group
tolerance
Excellent chemoselectivity
Great regioselectivity
Iridium- and Ruthenium-
catalyzed deoxygenation
methods is that these are
precious metals
Functional-group tolerant
Selective in both primary and
Benzylic alcohol2/21/2020 31
32. C-C Bond Formation
Grignard-Type Reactions
Represented examples for the Ru-catalyzed addition of hydrazone to aldehydes and ketones.
Ru-Catalyzed Addition of Hydrazones with
Aldehydes and Ketone
2/21/2020 32
33. Presynthesize the Hydrazones
Umpolung Carbanion
Metal free surrogates
Good chemoselectivity
Good functional group tolerance
Minor influence of the substituent
Relatively complex substrate
is also tolerated
Characteristics
2/21/2020 33
34. Proposed mechanism for the ruthenium-catalyzed Grignard type addition of umpolung hydrazones
to carbonyls
Proposed mechanism
A: Rapidly metalate
B: Rearrangement
C: Addition product(N2)
2/21/2020 34
N2
35. Classical strategies for amine synthesis
Nucleophilic addition of organometallic reagents
Coupling of carbonyl compounds with imines(Mannich reaction)>>> Enolate chemistry
Unpolung coupling of aldehydes and imines
Pinacol type coupling
Benzoin type coupling
Aldehydes as alkyl carbanion equivalents for Amine synthesis
Ru-Catalyzed Addition of Hydrazone with Imines
Scope of aldehydes for the Ru-catalyzed addition of umpolung hydrazones to imine
2/21/2020 35
36. Characteristics
[Ru(p-cymene)Cl2]2 providing the highest yield>>> The least expensive one
Favored by electron-rich phosphines(1,2-bis(dimethylphosphino)ethane (dmpe) and
tri(tert-butyl)-Phosphine
ligand-to-metal ratio(1:1)
K3PO4(Superior reactivity)
Cesium fluoride(CeF)>>>Additive
Removal of a chloride(Silver triflate)
Scope of Substrates
Aromatic aldehydes showed good reactivity
Halide substituents had a minor influence on the reactivity(Ortho-Least reactive)
Aromatic
Aliphatic
Heterocyclic
2/21/2020 36
37. Ru-Catalyzed Addition of Hydrazone with CO2
CO2 as a carbon feedstock
High abundance
Low cost
Low toxicity
Renewability
Umpolung carboxylation
Operationally simple
protocol
High reactivity
Selectivity under mild
conditions
Good functional group
tolerance
Readily scalable
2/21/2020 37
38. Cross-Coupling Reactions
Ni-Catalyzed Negishi-type Coupling
Efficient construction of C–C bonds
Ni(cod)2/PMe3 system with DBU
Electron-donating PMe3, PPh2Me,Or PPhMe2 were
effective
Chlorobenzene and fluorobenzene did not react
Ar-X Vinyl-X Alkyl-X
X= -Otf,Ots,Oms,Br,I etc…
2/21/2020 38
39. Tunable site selectivity between aryl iodide and tosylate
Broader substrate scope
Greater functional group compatibility
Chemoselectivity
Characteristics
2/21/2020 39
40. Proposed Mechanism
Proposed mechanism for the cross-couplings between aryl electrophiles
2/21/2020 40
Liu, Y. H.; Tang, D. L.; Cao, K. H.; Yu, L.; Han, J.; Xu, Q. J. Catal.2018
41. Pd-Catalyzed Tsuji–Trost Alkylation Reaction
Palladium-catalyzed allylic alkylation
Allylic electrophiles are less reactive
Using the electron-rich NHC ligand (IPr, 1,3-bis(2,6-diisopropylphenyl)
imidazole-2-ylidene)
Characteristics
Good functional group compatibility(ortho,meta,para)
Highly chemo- and regioselective C-alkylated products
High to excellent yields
2/21/2020 41
42. 2/21/2020 42
A tentative mechanism for the palladium-catalyzed allylic alkylation of umpolung carbonyls
43. Conclusion
Exploring synthetic
chemistry inspired
from old classical
reactions
provide a foundation
for the next generation
of chemical syntheses
towards sustainability
Develop fundamental
reaction tools for more
efficient and greener
chemical transformations
Efficient transformation of
natural abundant organic
compounds into chemical
products
44. 2/21/2020 44
Reference
(1) Kishner, N. J. Russ. Phys. Chem. Soc. 1911, 43, 582.
(2) Wolff, L. Justus Liebigs Ann. Chem. 1912, 394, 86.
(3) Li, J. J. Name Reactions, 5th ed; Springer: Switzerland, 2014.
(4) Kuethe, J. T.; Childers, K. G.; Peng, Z.; Journet, M.; Humphrey, G.R.; Vickery, T.; Bachert, D.; Lam, T. T. Org. Process
Res. Dev. 2009,13, 576.
(5) Huang-Minion J. Am. Chem. Soc.1946, 68, 2487
(6) Osdene, T. S.; Timmis, G. M.; Maguire, M. H.; Shaw, G.;Goldwhite, H.; Saunders, B. C.; Clark, E. R.; Epstein, P.
F.;Lamchen, M.; Stephen, A. M.; Tipper, C. F. H.; Eaborn, C.;Mukerjee, S. K.; Seshadri, T. R.; Willenz, J.; Robinson,
R.;Thomas, A. F.; Hickman, J. R.; Kenyon, J.; Crocker, H. P.; Hall, R.H.; Burnell, R. H.; Taylor, W. I.; Watkins, W. M.; Barton,
D. H. R.;Ives, D. A. J.; Thomas, B. R. J. Chem. Soc. 1955, 2038.
(7) Grundon, M. F.; Henbest, H. B.; Scott, M. D. J. Chem. Soc. 1963,1855.
(8) Caglioti, L.; Magi, M. Tetrahedron 1963, 19, 1127.
(9) Cram, D. J.; Sahyun, M. R. V. J. Am. Chem. Soc. 1962, 84, 1734.
(10) Furrow, M. E.; Myers, A. G. J. Am. Chem. Soc. 2004, 126, 5436.
(11) Corey, E. J.; Cheng, X.-M. The Logic of Chemical Synthesis; JohnWiley & Sons: New York, 1989.
(12) Grignard, V. Compt. Rend. 1890, 130, 1322.
(13) Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis;Pergamon Press: New York, 1992.
(14) Miyaura, N.; Yamada, K.; Suzuki, A. Tetrahedron Lett. 1979, 20,3437.
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Hydrazone formed converted cyclohexylhydrazine by Na metal in boiling ethanol ..unexpected product was cyclohexanol
ketone with hydrazine hydrate in ethanol under reflux, and then dried over fused potassium carbonate before further use
exothermic reaction
became self-sustaining, and external heating was no longer required
Wolff deduced that this reaction occurred through an intermediate hydrazone to give the dienone, which then tautomerized to the aromatic product
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