Categories: C=O Bond Formation >
Synthesis of enones
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α,β-unsaturated compounds (C-C Coupling) |
Recent Literature
Allylic alcohols were oxidized into aldehydes or ketones in the presence of
oxygen and Et3N using Pd(OAc)2 as catalyst. Diols with one
allylic function were selectively oxidized, with one of the hydroxyl groups
remaining untouched.
F. Batt, E. Bourcet, Y. Kassab, F. Fache, Synlett, 2007,
1869-1872.
The combination of TEMPO and CAN can be used for the aerobic oxidation of
benzylic and allylic alcohols into their corresponding carbonyl compounds.
However, steric hindrance has been observed to impede the reaction with some
substituted allylic systems. The present method is superior to others
currently available due to its relatively short reaction times and excellent
yields.
S. S. Kim, H. C. Jung, Synthesis, 2003, 2135-2137.
Pd/C in aqueous alcohol with molecular oxygen, sodium borohydride,
and potassium carbonate efficiently oxidized benzylic and allylic alcohols.
Sodium borohydride allows a remarkable reactivation of active sites of the Pd
surface.
G. An, M. Lim, K.-S. Chun, H. Rhee, Synlett, 2007, 95-98.
Dirhodium(II) caprolactamate effectively catalyzes the allylic oxidation of
a variety of olefins and enones with tert-butyl hydroperoxide as
terminal oxidant. The reaction is completely selective, tolerant of air and
moisture, and can be performed with as little as 0.1 mol % catalyst in
minutes.
A. E. Lurain, A. Maestri, A. R. Kelli, P. J. Carroll, P. J. Walsh, J. Am. Chem. Soc.,
2004, 126, 13622-13623.
Oxoammonium salts enable a practical and highly efficient oxidative
rearrangement of tertiary allylic alcohols to β-substituted α,β-unsaturated
carbonyl compounds. Acyclic substrates as well as medium membered ring
substrates and macrocyclic substrates can be oxidized.
M. Shibuya, M. Tomizawa, Y. Iwabuchi, J. Org. Chem., 2008,
73, 4750-4752.
The use of cationic silver (AgSbF4) as a catalyst for intra- and
intermolecular alkyne-carbonyl coupling is described. Intermolecular coupling proceeds
stereoselectively to afford trisubstituted enones.
J. U. Rhee, M. J. Krische, Org. Lett., 2005, 7, 2493-2495.
Catalytic (1,4-diazabicyclo[2.2.2]octane (DABCO) was found to be effective
for the isomerization of electron-deficient propargylic alcohols to E-enones
under mild conditions. When the substrate is conjugated with an amide,
addition of sodium acetate catalyzed the isomerization.
J. P. Sonye, K. Koide, J. Org. Chem., 2006, 71, 6254-6257.
A new and simple method is described for the one-step oxidation of α,β-enones
to 1,4-enediones in good yields using t-butylhydroperoxide as
stoichiometric oxidant and 20% Pd(OH)2 on carbon as catalyst. The same reagents have been used to convert ethylene ketals
of α,β-enones
to the corresponding monoethylene ketals of 1,4-enediones. The mechanism is
discussed.
J.-Q. Yu, E. J. Corey, J. Am. Chem. Soc., 2003, 125, 3232-3233.
A catalytic amount of Au(PPh3)NTf2 converts readily
accessible propargylic acetates into versatile linear α-iodoenones in good to
excellent yields. Very good Z-selectivities are observed for aliphatic
propargylic acetates.
M. Yu, G. Zhang, L. Zhang, Org. Lett., 2007,
9, 2087-2090.
A sequence of two gold(I)-catalyzed isomerization steps allows the synthesis
of
functionalized acetoxy bicyclo[3.1.0]hexenes from 5-en-2-yn-1-yl acetates.
Acetoxy bicyclo[3.1.0]hexene products can be further transformed to
2-cycloalkenones by simple methanolysis.
A. Buzas, F. Gagosz, J. Am. Chem. Soc., 2006, 128, 12614-12615.
A highly efficient carbon-carbon triple bond cleavage reaction of (Z)-enynols
offered a new route to highly substituted butenolides through a
gold(I)-catalyzed tandem cyclization/oxidative cleavage.
Y. Liu, F. Song, S. Guo, J. Am. Chem. Soc., 2006, 128, 11332-11333.
