Categories: C-C Bond Formation > Arenes >
α-Arylation
Recent Literature
A palladium-catalyzed coupling of aryl halides and ester enolates produced
α-aryl esters in high yields at room temperature. The reaction was highly
tolerant of functionalities and substitution patterns on the aryl halide.
Improved protocols for the selective monoarylation of tert-butyl
acetate and the efficient arylation of α,α-disubstituted esters were
developed with LiNCy2 as base and P(t-Bu)3 as ligand.
M. Jřrgensen, S. Lee, X. Liu, J. P. Wolkowski, J. F. Hartwig, J. Am. Chem. Soc., 2002,
124, 12557-12565.
Palladium-catalyzed α-arylations of chloroarenes with the sodium enolates of
tert-butyl propionate and methyl isobutyrate occur in high yields using P(t-Bu)3
as ligand. The reactions of chloroarenes with the Reformatsky reagent of tert-butyl
acetate were most challenging but occurred in high yields for chlorobenzene and
electron-poor chloroarenes.
T. Hama, J. F. Hartwig, Org. Lett., 2008,
10, 1549-1552.
The complex (IPr)Pd(acac)Cl has proven to be a highly active PdII
precatalyst in Buchwald-Hartwig reactions and α-ketone arylations of a wide
range of substrates including unactivated, sterically
hindered, and heterocyclic aryl chlorides.
N. Marion, E. C. Ecarnot, O. Navarro, D. Amoroso, A. Bell, S. P. Nolan, J. Org. Chem., 2006,
71, 3816-3821.
An improved protocol for the Pd-catalyzed α-arylation of aldehydes with aryl
halides allows the coupling of
an array of substrates including challenging electron-rich aryl bromides and
less reactive aryl chlorides. The utility of this method has been demonstrated
in a total synthesis of (±)-sporochnol.
R. Martín, S. L. Buchwald, Org. Lett.,
2008,
10, 4561-4564.
A catalytic asymmetric cross-coupling of α-halo carbonyl compounds with aryl
metal reagents generates synthetically useful α-aryl carboxylic acid derivatives
in good enantiomeric excess. The method can also be applied to enantioselective
alkenylation reactions.
X. Dai, N. A. Strotman, G. C. Fu, J. Am. Chem. Soc., 2008,
130, 3302-3303.
2-aryl-1,3-dicarbonyl compounds are produced in good yields by a CuI/L-proline-catalyzed
arylation of activated methylene compounds with aryl iodides and aryl
bromides in DMSO at 40-50°C in the presence of Cs2CO3.
X. Xie, G. Cai, D. Ma, Org. Lett.,
2005,
7, 4693-4695.
A general method for the Suzuki-Miyaura and
carbonyl enolate coupling of unactivated arenesulfonates was developed
utilizing Pd(OAc)2 and XPhos as ligand. The catalyst system effects
the coupling of various aryl, heteroaryl, and extremely hindered arylboronic acids
and carbonyl enolates with
different aryl tosylates, under mild conditions.
H. N. Nguyen, X. Huang, S. L. Buchwald, J. Am. Chem. Soc., 2003,
125, 11818-11819.
Reaction of β-bromo alcohols with 0.6 equiv of Et2Zn forms a zinc
complex in CH2Cl2 at room temperature, followed by
1,2-migration to give the corresponding carbonyl compounds. This mild and clean
rearrangement is general for acyclic and cyclic bromohydrins, and a variety of
ring-expansive and -contractive carbonyl compounds were obtained in very good
yields.
L. Li, P. Cai, Q. Guo, S. Xue, J. Org. Chem., 2008,
73, 3452-3459.
The use of zinc enolates (isolated Reformatsky reagents or generated in situ
from α-bromo amides or lithium enolates) instead of alkali metal enolates,
greatly expands the scope of the palladium-catalyzed α-arylation of aryl
bromides and vinyl bromides.
T. Hama, D. A. Culkin, J. F. Hartwig, J. Am. Chem. Soc.,
2006,
128, 4976-4985.
The coupling of aryl iodides and diethyl malonate in the presence of Cs2CO3 and catalytic amounts of CuI and 2-phenylphenol gave α-aryl malonates in good to excellent yields. This mild method tolerates various functional groups.
E. J. Hennessy, S. L. Buchwald, Org. Lett., 2002, 4, 269-272.
A one-pot procedure for the synthesis of 2-alkyl-2-arylcyanoacetates based on a
Pd(OAc)2/dppf-catalyzed enolate arylation followed by in situ
alkylation tolerates a diverse range of aryl and heteroaryl bromides, and
provides a rapid entry to a wide range of products in very good to yield.
X. Wang, A. Guram, E. Bunel, G.-Q. Cao, J. R. Allen, M. M. Faul, J. Org. Chem., 2008,
73, 1643-1645.
A general method for the direct α-arylation of nitriles with aryl chlorides
was developed. With a catalytic system generated from palladium and a commercially available
ligand, it is now possible to effect direct α-arylation using a wide variety of
starting materials.
J. You, J. G. Verkade, Angew. Chem., 2003,
115, 5205-5207.
A palladium-catalyzed α-arylation of nitriles was developed by exploring the structure and reactivity of arylpalladium cyanoalkyl complexes. The high yields and short reaction times observed for BINAP-ligated complexes suggested that BINAP-ligated palladium catalysts might be appropriate for the arylation of nitriles. Initial results on a palladium-catalyzed process for the direct coupling of aryl bromides and primary, benzylic, and secondary nitrile anions to form α-aryl nitriles in good yields are reported.
D. A. Culkin, J. F. Hartwig, J. Am. Chem. Soc., 2002,
124, 9330-9331.
Palladium-N-heterocyclic carbene (NHC) complexes were found to be
active catalysts for the arylation of various ketones with aryl chlorides,
bromides, and triflates in short reaction times.
M. S. Viciu, R. F. Germaneau, S. P. Nolan., Org.
Lett., 2002, 4, 4053-4056.
A convenient method has been developed for the palladium-catalyzed arylation of
malononitrile in high yields with aryl bromides and chlorides, respectively. The
influence of several reaction parameters such as base, ligand, solvent or
temperature were investigated.
A. Schnyder, A. F. Indolese, T. Maetzke, J. Wenger, H.-U. Blaser, Synlett, 2006,
3167-3168.
An efficient, mild, and general method for the C-arylation of β-enamino
esters and ketones with arynes provides a facile and direct access to various
substituted aromatic β-enamino compounds in good yield.
Y. K. Ramtohul, A. Chartrand, Org. Lett., 2007,
9, 1029-1032.
Cu-catalyzed asymmetric conjugate reduction of
β-substituted ketones leads to enantiomerically enriched
diphenylsilyl enol ethers, which are utilized in a diastereoselective Pd-catalyzed
α-arylation of various aryl bromides to yield disubstituted cycloalkanones with
excellent levels of enantiomeric and diastereomeric purity. The procedure can be
carried out in one-pot.
J. Chae, J. Yun, S. L. Buchwald, Org. Lett., 2004, 6, 4809-4812.
A very simple method for the α-arylation of N-protected
2-piperidinones in high yield is described. Key factors are the use of ZnCl2 and
Pd(dba)2 and the nature of the base.
A. de Filippis, D. G. Pardo, J. Cossy, Tetrahedron, 2004,
60,
9757-9767.
A small library of α,β-unsaturated oxindoles was
prepared by an efficient microwave-assisted one-pot sequence comprising an
aromatic substitution followed by an ionic Horner-Wadsworth-Emmons olefination.
A. Teichert, K. Jantos, K. Harms, A. Studer, Org. Lett., 2004,
6, 3477-3480.
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Palladium-catalyzed
alpha-Arylation of Esters, Ketones, Amides and Imides |
