Synthesis of aldehydes by deprotection or hydrolysis
A sequential hydroboration/Suzuki-Miyaura coupling of ynol ethers allows a highly regio- and stereoselective synthesis of stereodefined β,β-disubstituted alkenyl ethers. A number of functional groups are well-tolerated under the reaction conditions. Furthermore, the reaction enables a facile entry to labile diarylacetaldehydes by TFA-mediated hydrolysis of the β,β-disubstituted vinyl ethers.
W. Cui, M. Mao, Z. He, G. Zhu, J. Org. Chem., 2013, 78, 9815-9821.
A rapid and efficient oxidative deamination of various α-aminophosphonates allows the synthesis of α-ketophosphonates using ZnCr2O7 • 3 H2O under solvent-free conditions at room temperature. This method is also applicable to the rapid and highly selective oxidation of various amines to aldehydes and ketones in very good yields.
S. Sobhani, M. F. Maleki, Synlett, 2010, 382-386.
An efficient and convenient procedure has been developed for the hydrolysis of thioacetals/thioketals to the corresponding carbonyl compounds in excellent yields with o-iodoxybenzoic acid (IBX) in presence of β-cyclodextrin (β-CD) in water under neutral conditions at room temperature.
N. S. Krishnaveni, K. Surendra, Y. V. D. Nageswar, K. R. Rao, Synthesis, 2003, 2295-2297.
Deprotection of acetals and ketals can be achieved by using a catalytic amount of sodium tetrakis(3,5-trifluoromethylphenyl)borate (NaBArF4) in water at 30 °C. For example, a quantitative conversion of 2-phenyl-1,3-dioxolane into benzaldehyde was accomplished within five minutes.
C.-C. Chang, B.-S. Liao, S.-T. Liu, Synlett, 2007, 283-287.
Er(OTf)3 is a very gentle Lewis acid catalyst in the chemoselective cleavage of alkyl and cyclic acetals and ketals at room temperature in wet nitromethane.
R. Dalpozzo, A. De Nino, L. Maiuolo, M. Nardi, A. Procopio, A. Tagarelli, Synthesis, 2004, 496-498.
Perchloric acid adsorbed on silica gel is an extremely efficient, inexpensive, and reusable catalyst for the protection of aldehydes and ketones and the subsequent deprotection. Acetalization was mostly carried out under solvent-free conditions with trialkyl orthoformates, but weakly electrophilic carbonyl compounds and substrates that can coordinate with the catalyst, required the corresponding alcohol as solvent.
R. Kumar, D. Kumar, A. K. Chakraborti, Synthesis, 2007, 299-303.
Carbonyl compounds were obtained in very good yields after treatment of oximes with 2 molar equivalent of CuCl2 • 2 H2O at reflux in acetonitrile and water (4:1). In addition, cupric salt was readily recovered in an almost quantitative yield via the complete precipitation of Cu(OH)2 • 2 H2O.
N. Quan, X.-X. Shi, L.-D. Nie, J. Dong, R.-H. Zhu, Synlett, 2011, 1028-1032.
N-bromosaccharin is an efficient reagent for the oxidative cleavage of oximes to the corresponding aldehydes and ketones under microwave irradiation in a domestic microwave oven. This procedure features short reaction times, high chemoselectivity (no over-oxidation), easy work-up and high yields.
A. Khazaei, A. A. Manesh, Synthesis, 2004, 1739-1740.
Oximes of various aldehydes and ketones can be converted to the corresponding carbonyl compounds at room temperature in excellent yields with 2-iodylbenzoic acid in water in the presence of β-cyclodextrin.
N. S. Krishnaveni, K. Surendra, Y. V. D. Nageswar, K. R. Rao, Synthesis, 2003, 1968-1969.
A simple, mild and efficient procedure cleaves a wide range of ketoximes and aldoximes to the corresponding carbonyl compounds in an aqueous medium using catalytic amounts of potassium bromide and ammonium heptamolybdate tetrahydrate in combination with hydrogen peroxide.
N. C. Ganguly, S. K. Barik, Synthesis, 2008, 425-428.
I2 catalyzes the deprotection of oximes and imines to the corresponding carbonyl compounds under neutral conditions in a water/surfactant system at 25-40°C in high yields.
P. Gogoi, P. Hazarika, D. Konwar, J. Org. Chem., 2005, 70, 1934-1936.
Various aliphatic and aromatic oximes were converted to their corresponding aldehydes and ketones in good to excellent yields in the presence of 2-nitro-4,5-dichloropyridazin-3(2H)-one under microwave irradiation. It is noteworthy that the reaction is conducted under neutral, mild, and eco-friendly condition.
B. R. Kim, H.-G. Lee, E. J. Kim, S.-G. Lee, Y.-J. Yoon, J. Org. Chem., 2010, 75, 484-486.
Aqueous dimethylamine is an efficient reagent for the conversion of various benzal halides to their corresponding benzaldehydes. The method represents a novel, economical approach to acquire pure, substituted benzaldehydes from commercially available, or easily prepared starting materials.
D. Bankston, Synthesis, 2004, 283-289.
Geminal diacetates and dipivalates were prepared in high yields through a mild and efficient reaction of aldehydes with acetic anhydride or pivalic anhydride using zirconium (IV) chloride as a catalyst under solvent free conditions. Regeneration of aldehydes from the acylals was achieved using the same catalyst in methanol.
G. Smitha, Ch. S. Reddy, Tetrahedron, 2003, 59, 9571-9576.
The visible-light mediated oxidative C-C bond cleavage of aldehydes has been achieved in good yields at ambient temperature and open to air using Ru(bpy)3Cl2 as the photoredox catalyst.
H. Sun, C. Yang, F. Gao, Z. Li, W. Xia, Org. Lett., 2013, 15, 624-627.
Silylated cyanohydrins of iodo-substituted aryl, heteroaryl, or cycloalkenyl ketones undergo an I/Mg-exchange using i-PrMgCl·LiCl. After subsequent reactions with electrophiles, a facile deprotection produces polyfunctional ketones in good overall yiels. An extension to aromatic iodoaldehydes is described.
C.-Y. Liu, H. Ren, P. Knochel, Org. Lett., 2006, 8, 617-629.