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.
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.
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.
A simple method for the chemo- and regioselective, direct catalytic allylic alkylation of aldehydes and cyclic ketones has been developed. The combination of palladium and enamine catalysis furnished α-allylic alkylated aldehydes and cyclic ketones in high yields.
I. Ibrahem, A. Córdova, Angew. Chem. Int. Ed., 2006, 45, 1952-1956.
A catalytic enantioconvergent synthesis of quaternary stereocenters from racemates with quaternary stereocenters has been developed. A chiral Pd catalyst is involved in both the stereoablative (C-C bond-breaking) and stereoselective (C-C bond-forming) steps.
J. T. Mohr, D. C. Behenna, A. M. Harned, B. M. Stoltz, Angew. Chem. Int. Ed., 2005, 44, 6924-6927.
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.
A synergistic combination of copper and chiral amine catalysis enables an enantioselective α-vinylation of aldehydes using vinyl iodonium triflate salts. These mild catalysis provides enolizable α-formyl vinylic stereocenters without racemization or olefin transposition. These high-value coupling adducts are readily converted into various useful olefin synthons.
E. Skucas, D. W. C. MacMillan, J. Am. Chem. Soc., 2012, 134, 9090-9093.
A synergistic combination of copper and chiral amine catalysis enables an enantioselective α-alkenylation of aldehydes using boronic acids. The merger of two highly utilized and robust catalytic systems has allowed for the development of a mild and operationally trivial protocol for the direct formation of α-formyl olefins employing common building blocks for organic synthesis.
J. M Stevens. D. W. C. MacMillan, J. Am. Chem. Soc., 2013, 135, 11756-11757.
KOtBu/DMSO promoted α-vinylation of aliphatic, cycloaliphatic, and alkyl aromatic (heteroaromatic) ketones with diverse arylacetylenes enables the synthesis of various β,γ-unsaturated ketones of E configuration in very good yields.
B. A. Trofimov, E. Y. Schmidt, N. V. Zorina, E. V. Ivanova, I. A. Ushakov, J. Org. Chem., 2012, 77, 6880-6886.
A radical alkenylation reaction of α-halo carbonyl compounds with styrylindium dichloride as well as unactivated alkenylindiums proceeded in the presence of triethylborane. The geometry of the carbon-carbon double bonds was retained. Efficient one-pot strategies were developed.
K. Takami, H. Yorimitsu, K. Oshima, Org. Lett., 2004, 6, 4555-4558.
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.