Synthesis of 1,4-diketones
A Pd-catalyzed addition of organozinc reagents to enones in the presence of carbon monoxide provides 1,4-diketones in good yield. Cyclic and acyclic α,β-unsaturated ketones as well as aldehydes can be converted.
D. W. Custar, H. Le, J. P. Morken, Org. Lett., 2010, 12, 3760-3763.
Conjugated addition of primary nitroalkanes to α,β-unsaturated ketones or α,β-unsaturated esters, in the presence of two equivalents of DBU, allows the one-pot prepration of γ-diketones or γ-keto esters, respectively. The reaction of 2-aryl-1-nitroethane derivatives with α,β-unsaturated ketones gives cyclopentenones.
R. Ballini, L . Barboni, G. Bosica, D. Fiorini, Synthesis, 2002, 2725-2728.
A palladium-catalyzed cross-coupling of cyclopropanols and acyl chlorides enables a convenient method for preparing attractively functionalized 1,4-diketones. The utility of this method has been demonstrated in an enantioselective synthesis of (+)-myrmicarin 217.
B. B. Parida, P. P. Das, M. Niocel, J. K. Cha, Org. Lett., 2013, 15, 1752-1783.
Oxidative addition of In/InCl3 to enones proceeds exclusively in aqueous media and leads to water-tolerant, ketone-type indium homoenolates. The synthetic utility of the indium homoenolates was demonstrated through the synthesis of 1,4-dicarbonyl compounds via palladium-catalyzed coupling with acid chlorides.
Z.-L. Shen, K. K. K. Goh, H.-L. Cheong, C. H. A. Wong, Y.-C. Lai, Y.-S. Yang, T.-P. Loh, J. Am. Chem. Soc., 2010, 132, 15852-15855.
Iridium photoredox catalysis enables a decarboxylative 1,4-addition of 2-oxo-2-(hetero)arylacetic acids to various Michael acceptors including α,β-unsaturated ester, ketone, amide, aldehyde, nitrile, and sulfone at room temperature. 2-Oxo-2-(hetero)arylacetic acids are easily accessible precursors of acyl anions through photoredox-catalyzed radical decarboxylation.
G.-Z. Wang, R. Shang, W.-M. Cheng, Y. Fu, Org. Lett., 2015, 17, 4830-4833.
A Michael addition type reaction between aroyl chlorides and chalcones was realized in the presence of samarium metal in N,N-dimethylformamide as solvent. Various 1,4-diketones were synthesized in moderate to good yields. A possible mechanism is also discussed.
Y. Liu, Y. Li, Y. Qi, J. Wan, Synthesis, 2010, 4188-4192.
The merger of photoredox catalysis and primary amine catalysis enables a direct construction of all-carbon quaternary stereocenters via α-photoalkylation of β-ketocarbonyls with high efficacy and enantioselectivities.
Y. Zhu, L. Zhang, S. Luo, J. Am. Chem. Soc., 2014, 136, 14642-14645.