Synthesis of aldehydes
A (bpy)CuI/TEMPO catalyst system enables an efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and shows a high selectivity for 1° alcohols.
J. M. Hoover, S. S. Stahl, J. Am. Chem. Soc., 2011, 133, 16901-16910.
A convenient method enables the preparation of a silica gel supported TEMPO catalyst. The catalyst prepared from [4-hydroxy-TEMPO + NaCl]/SiO2 was used for an aerobic oxidation of alcohols to carbonyls under mild reaction conditions in the presence of Fe(NO3)3 • 9 H2O. Alcohols were converted to the corresponding carbonyls in good to excellent yields. After a simple filtration, the catalyst can be reused at least six times.
N. Tamura, T. Aoyama, T. Takido, M. Kodomari, Synlett, 2012, 1397-1407.
2-Iodoxybenzenesulfonic acid, which can be generated in situ from 2-iodobenzenesulfonic acid sodium salt, is a much more active catalyst than modified IBXs for the oxidation of alcohols with Oxone. Highly efficient and selective methods for the oxidation of alcohols to carbonyl compounds such as aldehydes, carboxylic acids, and ketones were established.
M. Uyanik, M. Akakura, K. Ishihara, J. Am. Chem. Soc., 2009, 131, 251-262.
A mild and efficient oxidation of alcohols with o-iodoxybenzoic acid (IBX) is catalyzed by β-cyclodextrin in a water/acetone mixture (86:14). Various alcohols were oxidized at room temperature in excellent yields.
K. Surendra, N. Srilakshmi Krishnaveni, M. Arjun Reddy, Y. V. D. Nageswar, K. Rama Rao, J. Org. Chem., 2003, 68, 2058-2059.
A novel, metal-free oxidation system for the catalytic synthesis of aldehydes and ketones using TEMPO and a quarternary ammonium salt as catalysts and Oxone as oxidant proved especially successful for the synthesis of ketones. The mild conditions tolerate even sensitive silyl protective groups which can otherwise be cleaved in the presence of Oxone.
C. Bolm, A. S. Magnus, J. P. Hildebrand, Org. Lett., 2000, 2, 1173-1175.
A highly efficient 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) catalyzed reaction using recyclable 1-chloro-1,2-benziodoxol-3(1H)-one as the terminal oxidant allows the conversion of various alcohols to their corresponding carbonyl compounds in high to excellent yields at room temperature in ethyl acetate, which is an environmentally friendly organic solvent.
X.-Q. Li, C. Zhang, Synthesis, 2009, 1163-1169.
A nitroxyl-radical-catalyzed oxidation using diisopropyl azodicarboxylate (DIAD) allows the conversion of various primary and secondary alcohols to their corresponding aldehydes and ketones without overoxidation to carboxylic acids. 1,2-Diols are oxidized to hydroxyl ketones or diketones depending on the amount of DIAD used.
M. Hayashi, M. Shibuay, Y. Iwabuchi, J. Org. Chem., 2012, 77, 3005-3009.
Tetrapropylammonium perruthenate enables oxidations of a wide range of molecules including examples of both double oxidations and selective oxidations. Mechanistic studies and general experimental procedures are reported. In addition several interesting developments in the chemistry of this reagent are outlined: heteroatom oxidation, cleavage reactions and use in sequential reaction processes.
S. B. Ley, J. Norman, W. P. Griffith, S. P. Marsden, Synthesis, 1994, 639-666.
A water-soluble Cp*Ir complex bearing a bipyridine-based functional ligand can be used as catalyst for a dehydrogenative oxidation of various primary and secondary alcohols to aldehydes and ketones, respectively without any oxidant. The catalyst can be reused.
R. Kawahara, K.-i. Fujita, R. Yamaguchi, J. Am. Chem. Soc., 2012, 134, 3643-3646.
Urea-hydrogen peroxide in the presence of a catalytic amount of magnesium bromide efficiently oxidizes primary and secondary benzylic alcohols into the corresponding aromatic aldehydes and ketones.
H. J. Park, J. C. Lee, Synlett, 2009, 79-80.
TEMPO-derived reagents tagged with multiple perfluoroalkyl chains and triazole moieties promote the oxidation of alcohols to aldehydes in organic solvent/water mixtures with reaction rates comparable to homogeneous TEMPO reagents, but can be easily recovered by liquid/emulsion filtration.
A. Gheorghe, T. Chinnusamy, E. Cuevas-Yañez, P. Hilgers, O. Reiser, Org. Lett., 2008, 10, 4171-4174.
A rapid oxidation of primary and secondary alcohols using catalytic amounts of TEMPO and Yb(OTf)3 in combination with a stoichiometric amount of iodosylbenzene afforded carbonyl compounds in excellent yields without over-oxidation. Oxidation of primary alcohols in the presence of secondary alcohols proceeded with good selectivity.
J.-M. Vatèle, Synlett, 2006, 2055-2058.
Optimized selective aerobic oxidations in ionic liquids convert various activated primary alcohols into their corresponding acids or aldehydes in good to excellent yields. The newly developed catalytic systems could also be recycled and reused for three runs without any significant loss of catalytic activity.
N. Jiang, A. J. Ragauskas, J. Org. Chem., 2007, 72, 7030-7033.
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.
The reaction of KBrO3 and NH2OH • HCl in situ generates NOx and Br anion, which allows in the presence of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) an activation of dioxygen to oxidize various benzylic alcohols quantitatively to their corresponding carbonyl compounds under mild conditions.
G. Yang, W. Wang, W. Zhu, C. An, X. Gao, M. Song, Synlett, 2010, 437-440.
A highly efficient and mild procedure for the oxidation of different types of alcohols uses TEMPO as catalyst, iodobenzene dichloride as stoichiometric oxidant, and pyridine as base. Oxidation of 1,2-diols gives α-hydroxy ketones or α-diketones depending on the amount of oxidant used. High yielding procedures for the preparation of iodoarene dichlorides have been developed.
X.-F. Zhao, C. Zhang, Synthesis, 2007, 551-557.
Keggin-type heteropoly acids revealed high catalytic activity for swift and selective oxidation of various hydroxy functionalities to the corresponding carbonyl groups using ferric nitrate as an oxidant under mild and solvent-free conditions.
H. Firouzabadi, N. Iranpoor, K. Amani, Synthesis, 2003, 408-412.
A new, green, mild and inexpensive system, I2-KI-K2CO3-H2O, selectively oxidized alcohols to aldehydes and ketones under anaerobic condition in water at 90 °C with excellent yields.
P. Gogoi, D. Konwar, Org. Biomol. Chem., 2005, 3, 3473-3475.
Pyridinium chlorochromate is a readily available, stable reagent, that oxidizes a wide variety of alcohols to carbonyl compounds with high efficiency.
E. J. Corey, J. W. Suggs, Tetrahedron Lett., 1975, 16, 2647-2650.
Permanganate supported on active manganese dioxide can be used effectively for the oxidation of arenes, alcohols and sulfides under heterogeneous or solvent-free conditions.
A. Shaabania, P. Mirzaeia, S. Naderia, D. G. Leeb, Tetrahedron, 2004, 60, 11415-11420.
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.
A new, highly recoverable palladium-based catalyst for the aerobic oxidation of alcohols combines an organic ligand and mesoporous channels that led to enhanced activity, prevention of agglomeration and the generation of a durable catalyst.
B. Karimi, S. Abedi, J. H. Clark, V. Budarin, Angew. Chem. Int. Ed., 2006, 45, 4776-4779.
A robust and effective Pd catalyst for the aerobic oxidation of various alcohols has been discovered. Using a slightly higher concentration of acetic acid as additive and extending the reaction times, the oxidation can be carried out under ambient atmosphere of air.
D. R. Jensen, M. J. Schultz, J. A. Mueller, M. S. Sigman, Angew. Chem. Int. Ed., 2003, 42, 3810-3813.
A chemoselective and efficient procedure allows the conversion of benzylic and allylic alcohols into the corresponding carbonyl compounds with sodium nitrate as oxidant in the presence of 3-methylimidazolinium hydrogensulfate.
A. R. Hajipour, F. Rafiee, A. E. Ruoho, Synlett, 2007, 1118-1119.
A four-component system consisting of acetamido-TEMPO/Cu(ClO4)2/TMDP/DABCO in DMSO allows an efficient room-temperature aerobic alcohol oxidation of various alcohols into their corresponding aldehydes or ketones in good to excellent yields. The catalytic system can be recycled.
N. Jiang, A. J. Ragauskas, J. Org. Chem., 2006, 71, 7087-7090.
The system Cu(ClO4)2/acetamido-TEMPO/DMAP catalyses the room-temperature aerobic oxidation of primary alcohols to aldehydes in the ionic liquid [bmpy]PF6. The catalysts can be recycled and reused.
N. Jiang, A. J. Ragauskas, Org. Lett., 2005, 7, 3689-3692.
The oxidation of primary and secondary alcohols by sodium percarbonate in the presence of catalytic amounts of both molybdenyl acetylacetonate and Adogen 464 gave fair to high yields of the corresponding carbonyl compounds.
S. Maignien, S. Aït-Mohand, J. Muzart, Synlett, 1996, 439-440.
[dibmim][BF4] can be used for the oxidation of alcohols to carbonyl compounds. This oxidizing agent offers a high degree of selectivity for the oxidation of primary alcohols to carbonyl compounds without oxidation to carboxylic acids in ionic liquids. [dibmim][BF4] can be reused after oxidation with peracetic acid.
W. Qian, E. Jin, W. Bao, Y. Zhang, Angew. Chem. Int. Ed., 2005, 44, 952-955.
An efficient oxidant-free oxidation for a wide range of alcohols was achieved by a recyclable ruthenium catalyst, which was prepared from readily available reagents through nanoparticle generation and gelation.
W.-H. Kim, I. S. Park, J. Park, Org. Lett., 2006, 8, 2543-2545.
Adsorbed [RuCl2(p-cymene)]2 on activated carbon is an efficient, environmentally attractive and highly selective catalyst for use in aerobic oxidations, hydrolytic oxidations and dehydrations. The heterogeneous catalyst was recovered quantitatively by simple filtration and could be reused with minimal loss of activity.
E. Choi, C. Lee, Y. Na, S. Chang, Org. Lett., 2002, 4, 2369-2371.
Benzyl alcohols and benzyl TBDMS ethers were efficiently oxidized to the corresponding carbonyl compounds in high yield with periodic acid catalyzed by CrO3 at low temperature (-78 °C). The oxidation procedure was highly functional group tolerant and very selective for the TBDMS group over the TBDPS group.
S. Zhang, L. Xu, M. L. Trudell, Synthesis, 2005, 1757-1760.
1 mol-% TEMPO and a catalytic amount of 1,3-dibromo-5,5-dimethylhydantoin and NaNO2 is a highly efficient catalytic system for the aerobic oxidations of benzylic alcohols in water.
R. Liu, C. Dong, X. Liang, X. Wang, X. Hu, J. Org. Chem., 2005, 70, 239-244.
A simple and mild TEMPO-CuCl catalyzed aerobic oxidation of primary and secondary alcohols in ionic liquid [bmim][PF6] gave the corresponding aldehydes and ketones with no trace of overoxidation to carboxylic acids. The product can be isolated by a simple extraction with organic solvent, and the ionic liquid can be recycled or reused.
I. A. Ansari, R. Gree, Org. Lett., 2002, 4, 1507-1509.
Benzylic ethers are oxidatively cleaved by 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate in wet MeCN at room temperature to give the corresponding aromatic aldehydes and alcohols in high yield. Primary and secondary alkyl alcohols are further oxidized to give carboxylic acids and ketones, respectively.
P. P. Pradhan, J. M. Bobbitt, W. F. Bailey, J. Org. Chem., 2009, 74, 9501-9504.
A highly convenient organocatalytic method for the mono-oxidation of unprotected glycosides relies on the chemoselective properties of TEMPO in combination with trichloroisocyanuric acid under very mild, basic conditions. The resulting dialdo-glycosides are efficiently purified with the use of solid-phase imine capture.
M. Angelin, M. Hermansson, H. Dong, O. Ramström, Eur. J. Org. Chem., 2006, 4323-4326.
Iodine was compared to other positive halogens as terminal oxidant in chemoselective oxidations of alcohols using catalytic TEMPO and was shown to be superior in cases of electron-rich and heteroaromatic benzylic alcohols.
R. A. Miller, R. S. Hoerrner, Org. Lett., 2003, 5, 285-287.
Oxidation of alcohols to aldehydes and ketones were performed under atmospheric oxygen with a catalytic amount of V2O5 in toluene at 100°C. Secondary alcohols can be chemoselectively converted into ketones in the presence of primary hydroxy groups.
S. Velusamy, T. Punniyamurthy, Org. Lett., 2004, 6, 217-219.
The use of PhI(OAc)2 in dichloromethane enables a clean oxidative cleavage of 1,2-diols to aldehydes. In the presence of OsO4 as catalyst, NMO and 2,6-lutidine, olefinic bonds can be cleaved in acetone/water to yield the corresponding carbonyl compounds.
K. C. Nicolaou, V. A. Adsool, C. R. H. Hale, Org. Lett., 2010, 12, 1552-1555.
A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldimethylsilyl (TBDMS) ethers, using the presence of PhIO or PhI(OAc)2 and catalytic amounts of metal triflates and TEMPO in THF or acetonitrile tolerates acid-sensitive protecting groups and leaves tert-butyldiphenylsilyl ethers and phenolic TBDMS groups untouched.
B. Barnych, J.-M. Vatèle, Synlett, 2011, 2048-2052.