Synthesis of Carbonyl Compounds by Alkylation or Condensation
A highly efficient α alkylation of ketones with primary alcohols by the use of a recyclable palladium catalyst has been demonstrated.
M. S. Kwon, N. Kim, S. H. Seo, I. S. Park, R. K. Cheedrala, J. Park, Angew. Chem., 2005, 117, 7073-7075.
In the presence of metal-ligand bifunctional iridium complex [Cp*Ir(2,2′-bpyO)(H2O)], a tandem acceptorless dehydrogenation/α-alkylation of secondary and primary alcohols provides α-alkylated ketones in high yields. This protocol offers complete selectivity for α-alkylated ketones and environmentally benign conditions.
R. Wang, J. Ma, F. Li, J. Org. Chem., 2015, 80, 10769-10776.
A Cp*Ir complex bearing a functional bipyridonate ligand is a highly effective and versatile catalyst for the α-alkylation of ketones with primary alcohols under environmentally benign and mild conditions. Furthermore, this complex also exhibited a high level of catalytic activity for the α-methylation of ketones with methanol.
F. Li, J. Ma, N. Wang, J. Org. Chem., 2014, 79, 10447-10455.
An unprecedented Rh-catalyzed direct methylation of ketones with N,N-dimethylformamide shows a broad substrate scope. Mechanistic studies suggest that DMF delivers a methylene fragment followed by a hydride during the methylation process.
Y. Li, D. Xue, W. Lu, C. Wang, Z.-T. Liu, J. Xiao, Org. Lett., 2014, 16, 66-69.
The Cu(acac)2-catalyzed cross-coupling of alkylzinc halides with α-chloroketones introduces primary and secondary alkyl groups adjacent to a ketone carbonyl under mild reaction conditions and in good yield. The reaction proceeds stereospecifically with inversion of stereochemistry.
C. F. Malosh, J. M. Ready, J. Am. Chem. Soc., 2004, 126, 10240-20241.
Indium(III) halide catalyzed the coupling of alkyl chlorides with silyl enolates derived from esters, ketones, and aldehydes to give various α-alkylated carbonyl compounds. A one-pot, three-component reactions of aldehyde enolates, alkyl chlorides, and allylsilanes or alkynylsilanes is described.
Y. Nishimoto, M. Yasuda, A. Baba, Org. Lett., 2007, 9, 4931-4934.
The use of 4-benzyl Hantzsch esters enables the construction of molecules with all-carbon quaternary centers by visible light-induced photoredox catalysis via transfer alkylation. Reactions of 4-alkyl Hantzsch nitriles as tertiary radical donors joined two contiguous all-carbon quaternary centers intermolecularly.
W. Chen, Z. Liu, J. Tian, J. Li, J. Ma, X. Cheng, G. Li, J. Am. Chem. Soc., 2016, 138, 12312-12315.
Photoirradiation of a mixture of acetone and water containing olefins affords the corresponding methyl ketones efficiently via a water-assisted C-C coupling between the acetonyl radical and olefins.
Y. Shiraishi, D. Tsukamoto, T. Hirai, Org. Lett., 2008, 10, 3117-3120.
An efficient and highly enantioselective conjugate addition of alkylzinc reagents to various cyclic nitroalkenes is promoted in the presence of 0.5-5 mol % (CuOTf)2·C6H6 and 1-10 mol % of chiral amino acid-based phosphine ligands at 0°C in toluene. Depending on the reaction conditions used, either the nitro or the corresponding α-substituted ketone product can be accessed.
C. A. Luchaco-Cullis, A. H. Hoveyda, J. Am. Chem. Soc., 2002, 124, 8192-8193.
Multifunctional palladium catalysis allows a one-pot stereocontrolled synthesis of tetrasubstituted methyl ketones and enynes. The homogeneous palladium dihalide catalyst is used for the bromo-/chloroallylation of alkynes and in situ for subsequent Wacker-Tsuji oxidation or Sonogashira cross-coupling.
A. N. Thadani, V. H. Rawal, Org. Lett., 2002, 4, 4321-4323.
A photo-organocatalytic enantioselective α- and γ-alkylation of aldehydes and enals with bromomalonates occurs under illumination by a fluorescent light bulb in the presence of a commercially available aminocatalyst without any external photoredox catalyst. Mechanistic investigations reveal the ability of transiently generated enamines to directly reach an electronically excited state while reactive radical species from the organic halides are formed.
M. Silvi, E. Arceo, I. D. Jurberg, C. Cassani, P. Melchiorre, J. Am. Chem. Soc., 2015, 137, 6120-6123.
Intramolecular halooxygenation and halothionation of N-allylcarboxamides/N-allylcarbothioamides proceeded readily in the presence of (diacetoxyiodo)benzene (PIDA) as the reaction promoter and halotrimethylsilane as the halogen source, providing the corresponding 5-halomethyloxazolines/5-halomethylthiazolines in very good yields. The 5-halomethyl products could be converted to different derivatives via nucleophilic substitution.
G.-Q. Liu, C.-H. Yang, Y.-M. Li, J. Org. Chem., 2015, 80, 11339-113550.