Synthesis of arylamines
CuI/4-hydroxy-l-proline-catalyzed coupling of aryl bromides and N-Boc hydrazine takes place in DMSO to give N-aryl hydrazides. When aryl iodides are employed, no ligand is required. Under the catalysis of CuI/4-hydroxy-l-proline, the coupling reaction of aqueous ammonia with aryl bromides proceeds smoothly to afford primary arylamines.
L. Jiang, X. Lu, H. Zhang, Y. Jiang, D. Ma, J. Org. Chem., 2009, 74, 4542-4546.
CuI-nanoparticles catalyze a selective synthesis of phenols, anilines, and thiophenols from aryl halides in the absence of both ligands and organic solvents. Anilines were formed selectively with ammonia competing with hydroxylation and thiophenols were generated selectively with sulfur powder after subsequent reduction competing with hydroxylation and amination.
H.-J. Xu, Y.-F. Liang, Z.-Y. Cai, H.-X. Qi, C.-Y. Yang, Y.-S. Feng, J. Org. Chem., 2011, 76, 2296-2300.
A complex generated from Pd[P(o-tol)3]2 and the alkylbisphosphine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings with this catalyst conducted with a solution of ammonia in dioxane form primary arylamines from various aryl electrophiles in high yields.
G. D. Vo, J. F. Hartwig, J. Am. Chem. Soc., 2009, 131, 11049-11061.
In a Pd-catalyzed arylation of ammonia with a wide range of aryl and heteroaryl halides, excellent selectivity for monoarylation was achieved under mild conditions or at rt by the use of bulky biarylphosphine ligands as well as their corresponding aminobiphenyl palladacycle precatalysts. As this process requires neither the use of a glovebox nor high pressures of ammonia, it should be widely applicable.
C. W. Cheung, D. S. Surry, S. L. Buchwald, Org. Lett., 2013, 15, 3734-3737.
Magnetically separable CuFe2O4 nanoparticles in a poly(ethylene glycol) medium are an inexpensive, nontoxic, environmentally benign, and recyclable system for the amination of various aryl iodides with aqueous ammonia to afford the corresponding aryl amines in good yields. The catalytic system was recycled five times with consistent activity.
A. S. Kumar, T. Ramani, B. Sreedhar, Synlett, 2013, 24, 843-846.
An efficient, fast and selective electrosynthesis of phenols and anilines from arylboronic acids in aqueous ammonia is achieved in an undivided cell. By simply changing the concentration of aqueous ammonia and the anode potential, good yields of phenols and anilines can be obtained chemoselectively.
H.-L. Qi, D.-S. Chen, J.-S. Ye, J.-M. Huang, J. Org. Chem., 2013, 78, 7482-7487.
A metal-free synthesis of primary aromatic amines from arylboronic acids affords structurally diverse primary arylamines in good chemical yields, including various halogenated primary anilines. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions, and can be scaled up to provide multigram quantities of anilines.
C. Zhu, G. Li, D. H. Ess, J. R. Falck, L. Kürti, J. Am. Chem. Soc., 2012, 134, 18253-18256.
The direct amination of alkyl and aryl pinacol boronates with lithiated methoxyamine provides aliphatic and aromatic amines, stereospecifically, and without preactivation of the boronate substrate.
S. N. Mlynarski, A. S. Karns, J. P. Morken, J. Am. Chem. Soc., 2012, 134, 16449-16451.
A facile and practical copper powder-catalyzed Ullmann amination of aryl halides with aqueous methylamine and other aliphatic primary amines under organic solvent- and ligand-free condition at 100°C and in air gave N-arylamines as sole products in very good yields. The presence of a small amount of air is essential. Secondary amines and aniline are not reactive. Sensitive substituents are tolerated.
J. Jiao, X.-R. Zhang, N.-H. Chang, J. Wang, J.-F. Wei, X.-Y. Shi, Z.-G. Chen, J. Org. Chem., 2011, 76, 1180-1183.
A metal-free synthesis of arylamines via the direct amination of phenols using easily accessible aminating reagents provides a versatile route to a broad range of arylamines with various functionalities in good yield. By using a two-step route of amination and oxidative coupling reaction, three naturally occurring carbazole alkaloids are synthesized from commercially available phenols: murrayafoline A, mukonine, and clausenine.
J. Yu, Y. Wang, P. Zhang, J. Wu, Synlett, 2013, 24, 1448-1454.
In the presence of Pd(OAc)2, PhB(OH)2, and a hindered and electron-rich MOP-type ligand, a variety of primary aryl amines reacted with various aryl tosylates to form the corresponding secondary aryl amines in high yields with high selectivity. Furthermore, the catalyst system was also efficient for the arylation of indoles and hydrazones with aryl tosylates.
X. Xie, G. Ni, F. Ma, L. Ding, S. Xu, Z. Zhang, Synlett, 2011, 955-958.
The arylation of N-H and O-H containing compounds at room temperature with phenylboronic acids is promoted in the presence of cupric acetate and a tertiary amine. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides.
D. M. T. Chan, K. L. Monaco, R.-P. Wang, M. P. Winteres, Tetrahedron Lett., 1998, 39, 2933-2936.
NiCl2· 6 H2O is an efficient catalyst for the cross-coupling of arylboronic acids with various N-nucleophiles. The method is practical and offers an alternative to the corresponding Cu-mediated Chan-Lam coupling.
D. S. Raghuvanshi, A. K. Gupta, K. N. Singh, Org. Lett., 2012, 14, 4326-4329.
A rhodium-catalyzed amination reaction of aryl halides with amines takes place in the presence of a N-heterocyclic carbene ligand. The active metal species responsible for the reaction progress was identified. This convenient and mild procedure for Rh-catalyzed N-arylation displays a wide range of substrate scope and high degree of functional group tolerance.
M. Kim, S. Chang, Org. Lett., 2010, 12, 1640-1643.
An efficient, transition metal catalyst-free amination of aryl halides under microwave irradiation is a particularly powerful method for the coupling of electron-rich aryl halides with various amines. Meta-substituted anilines have been prepared from ortho- or para-substituted phenylhalides. A mechanism via a benzyne intermediate has been proposed.
L. Shi, M. Wang, C.-A. Fan, F.-M. Zhang, Y.-Q. Tu, Org. Lett., 2003, 5, 3515-3517.
Pd-catalyzed intermolecular aerobic dehydrogenative aromatizations enable the arylation of amines with cyclohexanones and 2-cyclohexen-1-ones. Under optimized reaction conditions, primary and secondary amines are selectively arylated in good yields under an atmosphere of molecular oxygen.
S. A. Girard, X. Hu, T. Knauber, F. Zhou, M.-O. Simon, G.-J. Deng, C.-J. Li, Org. Lett., 2012, 14, 5606-5609.
Amides are excellent N-sources in the NHC-Pd(II)-Im complex catalyzed amination of aryl chlorides. In the presence of KOtBu, various aryl chlorides and amides react smoothly to give the corresponding aminated products in good yields at room temperature within 6 h.
W.-X. Chen, L-X. Shao, J. Org. Chem., 2012, 77, 9236-9239.
The use of arylboroxines and O-benzoyl hydroxylamines as coupling partners enables a transition-metal-free strategy to construct C(sp2)-N bonds. This transformation provides a useful method to access various aromatic amines.
Q. Xiao, L. Tian, R. Tan, Y. Xia, D. Qiu, Y. Zhang, J. Wang, Org. Lett., 2012, 14, 4230-4233.
A catalyst system based on a new biarylmonophosphine ligand shows excellent reactivity for C-N cross-coupling reactions. This catalyst system enables the use of aryl mesylates as a coupling partner and permits a highly selective monoarylation of an array of primary aliphatic amines and anilines at low catalyst loadings and with fast reaction times.
B. P. Fors, D. A. Watson, M. R. Biscoe, S. L. Buchwald, J. Am. Chem. Soc., 2008, 130, 13552-13554.
A silane-promoted nickel-catalyzed amination of aryl chlorides with a catalytic amount of Ni(acac)2 and 3,5,6,8-tetrabromo-1,10-phenanthroline as ligand in the presence of polymethylhydrosiloxane gives the desired (het)arylamines in good yields. The reaction is sensitive to the nature and amount of the silane promoter.
G. Manolikakes, A. Gavryushin, P. Knochel, J. Org. Chem., 2008, 73, 1429-1434.
Air- and moisture-stable Ni(II)-(σ-aryl) complexes, associated with N-heterocyclic carbene ligands, produce a catalytically active Ni(0) species in situ for an efficient amination of aryl chlorides with anilines and secondary cyclic amines under mild conditions.
C. Chen, L-M. Yang, J. Org. Chem., 2007, 72, 6324-6327.
Aryl triflates substituted with both electron-poor and electron-rich groups are effectively converted to the corresponding anilines under microwave irradiation in 1-methyl-2-pyridone (NMP) without base and catalyst. It is noteworthy that halogenated aryl triflates chemoselectively afford halogenated anilines.
G. Xu, Y.-G. Wang, Org. Lett., 2004, 6, 985-987.
A nickel complex derived from dppf, along with NaOt-Bu as the base, enabled challenging aminations of aryl sulfamates. Palladium-catalyzed aminations of imidazolylsulfonates with rac-BINAP as the ligand offer an improved functional group tolerance.
L. Ackermann, R. Sandmann, W. Song, Org. Lett., 2011, 13, 1784-1786.
N-Arylation of azoles and amines with arylboronic acids was efficiently carried out with heterogeneous copper(I) oxide in methanol at room temperature under base-free conditions. Various arylboronic acids and amines were converted to the corresponding N-arylazoles and N-arylamines in very good yields, demonstrating the versatility of the reaction.
B. Sreedhar, G. T. Venkanna, K. B. S. Kumar, V. Balasubrahmanyam, Synthesis, 2008, 795-799.
The reaction of di-tert-butyl dicarbonate or a chloroformate and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide. The acyl azide undergoes a Curtius rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea.
H. Lebel, O. Leogane, Org. Lett., 2006, 8, 5717-5720.
An efficient, mild and transition-metal-free N-arylation of amines, sulfonamides, and carbamates and O-arylation of phenols and carboxylic acids has been achieved by using various o-silylaryl triflates in the presence of CsF.
Z. Liu, R. C. Larock, J. Org. Chem., 2006, 71, 3198-3209.
A copper-catalyzed electrophilic amination of simple and functionalized aryl, heteroaryl-, benzyl, n-alkyl, sec-alkyl, and tert-alkyl diorganozinc nucleophiles with R2NOC(O)Ph and RHNOC(O)Ph reagents as electrophilic nitrogen sources provides tertiary and secondary amines, respectively, in generally good yields. In many cases, the product may be isolated analytically pure after a simple extractive workup. A Cu-catalyzed amination of Grignard reagents using cocatalysis by ZnCl2 is described.
A. M. Berman, J. S. Johnson, J. Org. Chem., 2006, 71, 219-224.
Zn[N(SiMe3)2]2 is a mild ammonia equivalent and base for the palladium-catalyzed amination of aryl halides and triflates. The combination of Zn[N(SiMe3)2]2 and LiCl coupled with aryl halides containing base-sensitive functionality in high yields.
D.-Y. Lee, J. F. Hartwig, Org. Lett., 2005, 7, 1169-1172.
The NiCl2(PPh3)2-PPh3-catalyzed cross-coupling of bromomagnesium diarylamides, generated in situ from diarylamines, with aryl bromides or iodides is an inexpensive, convenient, and practical method for the synthesis of triarylamines.
C. Chen, L.-M. Yang, Org. Lett., 2005, 7, 2209-2211.
1,1,1-Trimethylhydrazinium Iodide: A Novel, Highly Reactive Reagent for Aromatic Amination via Vicarious Nucleophilic Substitution of Hydrogen
P. F. Pagoria, A. R. Mitchell, R. D. Schmidt, J. Org. Chem., 1996, 61, 2934-2935.
Pyridine N-oxides were converted to 2-aminopyridines in a one-pot fashion using Ts2O-tBuNH2 followed by in situ deprotection with TFA. The amination proceeded in high yields, excellent 2-/4-selectivity, and with good functional group compatibility.
J. Yin, B. Xiang, M. H. Huffman, C. E. Raab, I. W. Davies, J. Org. Chem., 2007, 72, 4554-4557.
A facile metal-free oxidative amination of benzoxazole by activation of C-H bonds with secondary or primary amines in the presence of catalytic iodine in aqueous tert-butyl hydroperoxide proceeds smoothly at ambient temperature under neat reaction condition to furnish products in high yields. This user-friendly method produces only tertiary butanol and water as byproducts.
M. Lamani, K. R. Prabhu, J. Org. Chem., 2011, 76, 7938-7944.