Synthesis of α-keto carboxylic acids, esters and amides
A tandem three-step, one-pot method for the conversion of aldehydes into β-substituted-2-oxohex-5-enoic acids in good to excellent yield is described. The optimised sequence is carried out in water with microwave irradiation and involves sequential Horner-Wadsworth-Emmons (HWE) olefination, Claisen rearrangement and ester hydrolysis. The outcome of this domino sequence can be controlled by the temperature of the process.
E. Quesada, R. J. K. Taylor, Synthesis, 2005, 3193-3195.
A versatile and highly efficient method for the direct synthesis of α-keto esters and 1,2-diketones utilizes an oxidative cleavage of various β-keto esters and 1,3-diketones by an Oxone/aluminum trichloride system. The simple, environmentally benign one-step oxidation reaction proceeded selectively in aqueous media to afford products in high yields and short reaction times.
A. Stergiou, A. Bariotaki, D. Kalaitzakis, I. Smonou, J. Org. Chem., 2013, 78, 7268-7273.
A general Pd-catalyzed double carbonylation of aryl iodides with secondary or primary amines provides α-ketoamides in high yields with excellent chemoselectivities at atmospheric CO pressure. This transformation proceeds successfully even at room temperature and in the absence of any ligand and additive.
H. Du, Q. Ruan, M. Qi, W. Han, J. Org. Chem., 2015, 80, 7816-7823.
While 3,4;5,6-di-O-isopropylidene-N-phthaloyl-D-glucosamine propane-1,3-diyl dithioacetal underwent fast β-elimination, the corresponding N-acetyl derivative was easily deprotonated with butyllithium to form the dilithiated intermediate. Stoichiometry and temperature were crucial factors for selective C-C coupling with various electrophiles.
Y.-L. Chen, R. Leguijt, H. Redlich, R. Fröhlich, Synthesis, 2006, 4212-4218.