Categories: C-C Bond Formation > Oxygen-, Nitrogen-containing molecules > Active methylenes >
Benzylations
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Recent Literature
A nickel-catalyzed benzylic substitution of pimary and secondary benzyl
2,3,4,5,6-pentafluorobenzoates with a wide variety of malonate derivatives
provides the corresponding alkylation products in good yields.
H. Tsuji, K. Hashimoto, M. Kawatsura,
Org. Lett., 2019, 21, 8837-8841.
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.
Carreira's chiral Ir/(P, olefin)
complex enables an enantioselective allylic alkylation of branched racemic allylic
alcohols with malonates with excellent enantioselectivity. The malonates could be
used directly as efficient nucleophiles without the need for preactivation.
C.-Y. Meng, X. Liang, K. Wei, Y.-R. Yang, Org. Lett., 2019, 21,
840-843.
An enantioselective iridium-catalyzed allylic alkylation of malonates with
trisubstituted allylic electrophiles at ambient temperature provides all-carbon
quaternary stereocenters. The quaternary products can be readily converted to
several valuable building blocks such as vicinal quaternary products and
β-quaternary acids.
F. A. Moghadam, E. F. Hicks, Z. P. Sercel, A. Q. Cusumano, M. D. Bartberger,
B. M. Stoltz, J. Am. Chem. Soc.,
2022, 144, 7983-7987.
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.
Iridium catalyzes a branch-selective hydroalkylation of simple aliphatic and
aromatic alkenes with malonic amides and malonic esters under neutral reaction
conditions. A substrates bearing bromine, chlorine, ester, 2-thienylcarboxylate,
silyl, and phthalimide groups are suitable for this hydroalkylation. Selective
transformations of hydroalkylated products to 1,3-diamines or monoamides are
reported.
T. Sawano, M. Ono, A. Iwasa, M. Hayase, J. Funatsuki, A. Sugiyama, E.
Ishikawa, T. Yoshikawa, K. Sakata, R. Takeuchi, J. Org. Chem., 2023, 88,
1545-1559.
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.
F. Stauffer, R. Neier, Org. Lett., 2000, 2, 3535-3537.
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.
CuO catalyzes a three-component reaction of α-ketoaldehydes, 1,3-dicarbonyl
compounds, and organic boronic acids in water to provide a wide range of
products containing 1,3- and 1,4-diketones. The method offers use of readily
available starting materials, wide substrate scope, excellent yields, gram-scale
synthesis, and mild reaction conditions.
Q. Xia, X. Li, X. Fu, Y. Zhou, Y. Peng, J. Wang, G. Song, J. Org. Chem., 2021, 86,
9914-9923.
Related
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.