A palladium complex generated in situ from [Pd(η3-C3H5)(cod)]BF4 and DPPF is a good catalyst for benzylations of malonates with a wide range of benzyl methyl carbonates. The DPEphos ligand is superior to DPPF in the case of palladium-catalyzed benzylic amination of benzylic esters.
R. Kuwano, Y. Kondo, Y. Matuyama, J. Am. Chem. Soc., 2003, 125, 12104-12105.
The reaction of 1,3-diketones, ketoesters, and ketoamides under non-anhydrous conditions with substituted 1-phenylethanols gave benzylated products in high yields in the presence of rare earth metal and hafnium triflates as catalysts. The allylation of a diketone with allylic alcohols was also possible. Catalysts can be recovered by water extraction and reused up to five times.
M. Noji, Y. Konno, K. Ishii, J. Org. Chem., 2007, 72, 5161-5167.
Perchloric acid-catalyzed additions of various β-dicarbonyl compounds to a series of secondary alcohols and alkenes could be conveniently conducted in commercial solvent and gave good yields. Moreover, silica gel-supported HClO4 could also catalyze the heterogeneous addition for a series of substrates with similar or even higher yields. The supported catalyst could be readily recovered and reused for four runs.
P. N. Liu, L. Dang, Q. W. Wang, S. L. Zhao, F. Xia, Y. J. Ren, X. Q. Gong, J. Q. Chen, J. Org. Chem., 2010, 75, 5019-5020.
An efficient bismuth-catalyzed hydroalkylation of various styrenes, norbornene, and cyclohexadiene with 1,3-dicarbonyl compounds provides the corresponding alkylated pentanediones in good yields after short reaction times.
M. Rüping, B. J. Nachtsheim, A. Künkel, Synlett, 2007, 1391-1394.
A highly effective bismuth-catalyzed benzylation and allylic alkylation of 2,4-pentanediones with free alcohols provides the corresponding monoalkylated dicarbonyl compounds in high yields after short reaction times. In addition, a new route to substituted indenes is presented.
M. Rüping, B. J. Nachtsheim, A. Künkel, Org. Lett., 2007, 9, 825-828.
A mild and direct indium-catalyzed process for the C-C bond formation from alcohols and active methylenes, alkoxyketones or indoles was developed.
M. Yasuda, T. Somyo, A. Baba, Angew. Chem. Int. Ed., 2006, 45, 793-794.
An expeditious synthesis of α-substituted tert-butyl acrylates from commercially available aldehydes and Meldrum's acid includes a telescoped condensation-reduction sequence to afford 5-monosubstituted Meldrum's acid derivatives followed by a Mannich-type reaction triggered by a rapid cycloreversion of the dioxinone ring on heating with tert-butyl alcohol.
C. G. Frost, S. D. Penrose, R. Gleave, Synthesis, 2009, 627-635.
A powerful one-pot method for the reductive alkylation of stoichiometric amounts of malononitrile with aromatic aldehydes incorporates water as the catalyst in ethanol for the condensation step. The subsequent reduction step takes place quickly and efficiently with sodium borohydride to give monosubstituted malononitriles.
F. Tayyari, D. E. Wood, P. E. Fanwick, R. E. Sammelson, Synthesis, 2008, 279-285.
Hantzsch ester as reducing agent enables a cascade Knoevenagel condensation-reduction approach in water. Various reduced Knoevenagel adducts could be easily prepared by direct alkylation of malononitrile, ethyl 2-cyanoacetate, and 2-(4-nitrophenyl)acetonitrile, respectively.
T. He, R. Shi, Y. Gong, G. Jiang, M. Liu, S. Qian, Z. Wang, Synlett, 2016, 27, 1864-1869.
Knoevenagel condensation followed by hydrogenation with triethylamine-formic acid in the presence of a ruthenium-amido complex allowed an α-alkylation of various nitriles with carbonyl compounds in good yields. The reaction tolerated various functional groups, including nitro and chloro groups, and a furan ring.
H. Sun, D. Ye, H. Jiang, K. Chen, H. Liu, Synthesis, 2010, 2577-2582.
A highly enantioselective catalytic alkylation of cyanoacetates was achieved using a chiral phase-transfer catalyst to give α,α-disubstituted α-cyanoacetates which have a chiral quaternary carbon.
K. Nagata, D. Sano, T. Itoh, Synlett, 2007, 547-550.
The synthesis and properties of different planar chiral 1-phosphino-2-sulfenylferrocene ligands are reported. Very high enantioselectivities were obtained in the palladium-catalyzed allylic substitution of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate (ee's up to 97%) and nitrogen nucleophiles (ee's up to 99.5%) using the readily available tert-butylsulfenyl derivatives.
O. G. Mancheno, J. Priego, S. Cabrera, R. G. Arrayas, T. Llamas, J. C. Carretero, J. Org. Chem., 2003, 68, 3679-3686.
A series of trialkylsilylated chiral aminophosphine ligands are prepared from (S)-prolinol and applied to a palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with a dimethyl malonate-BSA-LiOAc system.
Y. Tanaka, T. Mino, K. Akita, M. Sakamoto, T. Fujita, J. Org. Chem., 2004, 69, 6679-6687.
Bis-pyridylamides were used in a regioselective Molybdenium-catalyzed asymmetric allylation of carbonates. 4-substituted pyridyl ligands exhibited high regioselectivity and enantioselectivity, whereas 6-substituted ligands afforded no product under the same conditions.
O. Belda, C. Moberg, Synthesis, 2002, 1601-1603.
Very efficient reactions of Baylis-Hillman adducts with iodobenzenes using commercially available palladium-on-carbon as a catalyst under solvent-free conditions afforded α-benzyl-β-keto esters in very good yields.
H.-S. Kim, S.-J. Lee, B. Choi, C. M. Yoon, Synthesis, 2012, 44, 3161-3164.
An improved Heck reaction allows the synthesis of various α-benzyl-β-keto esters from aryl bromides and Baylis-Hillman adducts for use in the preparation of new pharmaceutical agents.
N. J. Bennett, A. Goldby, R. Pringle, Synlett, 2010, 1688-1690.