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Synthesis of 2-quinolones

Recent Literature

A Pd-catalyzed C-H bond activation/C-C bond formation/cyclization cascade process enables the synthesis of quinolinone derivatives from simple anilines as the substrates. This method provides access to quinolinone-containing alkaloids and drug molecules.
J. Wu, S. Xiang, J. Zeng, M. Leow, X.-W. Liu, Org. Lett., 2015, 17, 222-225.

The combination of palladium catalysis and iridium photocatalysis enables a general catalytic anti-hydroarylation of electron-deficient internal alkynes with a broad range of arylboronic acids. The reaction of ortho-substituted boronic acids provides pharmaceutically relevant heterocyclic cores via a cascade process.
J. Corpas, P. Mauleón, R. G. Arrayás, J. C. Carretero, Org. Lett., 2020, 22, 6473-6478.

Various aryl alkynoates and alkynanilides undergo fast intramolecular reaction at room temperature in the presence of a catalytic amount of Pd(OAc)2 and trifluoroacetic acid (TFA) as solvent to afford coumarins and quinolinones in good yields. The reaction tolerates a number of functional groups such as Br and CHO.
C. Jia, D. Piao, T. Kitamura, Y. Fujiwara, J. Org. Chem., 2000, 65, 7516-7522.

A metal-free CH [5 + 1] carbonylative annulation of 2-alkenyl/pyrrolylanilines with dioxazolones as carbonylating reagents provides privileged quinolinones and pyrrolyl-fused quinoxalinones. This process features exceedingly simple operation and tolerates both vinyl and aryl substrates. Formation of an isocyanate intermediate plays a crucial role in the carbonylation annulation.
J. Nan, P. Chen, X. Gong, Y. Hu, Q. Ma, B. Wang, Y. Ma, Org. Lett., 2021, 23, 3761-3766.

A hypervalent iodine(III)-mediated intramolecular decarboxylative Heck-type reaction of 2-vinyl-phenyl oxamic acids provides various 2-quinolinones with excellent chemoselectivity at room temperature via a unique ring-strain-enabled radical decarboxylation mechanism. This protocol features metal-free reaction conditions and operational simplicity.
H. Fan, P. Pan, Y. Zhang, W. Wang, Org. Lett., 2018, 20, 7929-7932.

A palladium-catalyzed synthesis of 3-arylquinolin-2(1H)-ones proceeds through a reductive aminocarbonylation of benzylic ammonium triflates with o-nitrobenzaldehydes. The reaction provides a wide range of 3-arylquinolin-2(1H)-ones in good yields with very good functional group compatibility.
Y. Liu, X. Qi, X.-F. Wu, J. Org. Chem., 2021, 86, 13824-13832.

The combination of iron(III)chloride, tert-butyl nitrite (TBN), and N-hydroxyphthalimide (NHPI) catalyzes a direct aerobic α,β-dehydrogenation of carbonyls. A large variety of lactams and flavanones as well as coumarin and thiochromen-4-one could be produced via this transition-metal-free method in high yields.
G.-Q. Jiang, B.-H. Han, X.-P. Cai, J.-P. Qu, Y.-B. Kang, Org. Lett., 2023, 25, 4429-4433.

A general and efficient reaction of readily available N-methyl-N-phenylcinnamamides with phenyliodine bis(trifluoroacetate) (PIFA) in the presence of Lewis acids provides various 3-arylquinolin-2-one compounds in good yields. This novel approach features not only metal-free oxidative C(sp2)-C(sp2) bond formation but also an exclusive 1,2-aryl migration.
L. Liu, H. Lu, H. Wang, C. Yang, X. Zhang, D. Zhang-Negrerie, Y. Du, K. Zhao, Org. Lett., 2013, 15, 2903-2909.

A Ru-catalyzed cyclization of anilides with propiolates or acrylates affords 2-quinolones having diverse functional groups in good to excellent yields. 2-quinolinones can be converted into 3-halo-2-quinolinones and 2-chloroquinolines.
R. Manikandan, M. Jeganmohan, Org. Lett., 2014, 16, 3568-3571.

The employment of hydrophobic ionic liquids dramatically enhanced the activity of metal triflates in Friedel-Crafts alkenylations of aromatic compounds with various alkyl- and aryl-substituted alkynes.
C. E. Song, D.-U. Jung, S. Y. Choung, E. J. Roh, S.-G. Lee, Angew. Chem., 2004, 116, 6309-6311.

Visible-light-driven hydrocarboxylations as well as carbocarboxylations of alkynes using CO2 via an iridium/cobalt dual catalysis provide access to various pharmaceutically important heterocycles in a one-pot procedure from readily available alkynes. Coumarins, 2-quinolones, and 2-benzoxepinones were directly accessed through a one-pot alkyne hydrocarboxylation/alkene isomerization/cyclization sequence.
J. Hou, A. Ee, W. Feng, J.-H. Xu, Y. Zhao, J. Wu, J. Am. Chem. Soc., 2018, 140, 5257-5263.

An attractive palladium-catalyzed reductive aminocarbonylation reaction of o-iodophenol-derived allyl ethers with o-nitrobenzaldehydes provides 3-alkenylquinolin-2(1H)-one derivatives in very good yields in the presence of Mo(CO)6 as both CO surrogate and reductant.
J.-L. Liu, W. Wang, X. Qi, X.-F. Wu, Org. Lett., 2022, 24, 2248-2252.

A Pd(OAc)2-catalyzed cyclization of N-(2-formyl­aryl)alkynamides provides an efficient and atom-economical synthesis of 2-quinolinone derivatives via oxypalladation of alkynes.
J. Zhang, X. Han, X. Lu, Synlett, 2015, 26, 1744-1748.

A silver-catalyzed method provides a practical, highly efficient, and straightforward route to substituted quinolin-2-ones or 3,4-dihydroquinolin-2-ones in one step through an intermolecular radical addition/cyclization in aqueous solution. A mechanism for the formation of quinolin-2-ones is proposed.
W.-P. Mai, G.-C. Sun, J.-T. Wang, G. Song, P. Mao, L.-R. Yang, J.-W. Yuan, Y.-M. Xiao, L.-B. Qu, J. Org. Chem., 2014, 79, 8094-8102.

A facile and efficient intramolecular cyclization of readily available N-aryl cinnamides is promoted by triflic anhydride in N,N-dimethyl trifluoroacetamide (DTA) under mild conditions to provide polysubstituted quinolin-2(1H)-ones.
Q. Zhang, J. Yuan, M. Yu, R. Zhang, Y. Liang, P. Huang, D. Dong, Synthesis, 2017, 49, 4996-5002.

A rapid synthesis of quinolines from 2-alkenylanilines involves an unexpected DMAP-catalyzed cyclization of 2-alkenylanilines with di-tert-butyl dicarbonate providing a series of tert-butyl quinolin-2-yl carbonates with various functional groups in good yields under mild conditions. Furthermore, the tert-butyl quinolin-2-yl carbonate can be easily converted into corresponding quinolinones and 2-(pseudo)haloquinolines.
Y.-N. Huang, Y.-L. Li, J. Li, J. Deng, J. Org. Chem., 2016, 81, 4645-4653.

A Sc(OTf)3-catalyzed ring-closing alkyne-carbonyl metathesis enables an atom-economical construction of densely substituted 4-acyl-2-quinolones from N-(2-alkynylphenyl)-α-ketoamides. Mechanistic studies support a formation of an oxetene intermediate and an electrocyclic ring-opening of the oxetene.
Z. Su, S. Wang, J. Org. Chem., 2022, 87, 16873-16881.

An annulation of 2-cyanoaryl acrylamides via C=C double bond cleavage enables a facile and efficient synthesis of functionalized 4-amino-2-quinolones, which are important N-heterocycles. In this transformation, a THF radical plays a crucial role.
W.-J. Xia, T.-G. Fan, Z.-W. Zhao, X. Chen, X.-X. Wang, Y.-M. Li, Org. Lett., 2021, 23, 6158-6163.

4-hydroxyquinolin-2(1H)-one derivatives have attracted much attention due to their biological benefits, but up to now harsh reactions conditions must be employed to provide these key compounds. Various o-alkynylanilines can be converted under mild reaction conditions to 4-hydroxyquinolin-2(1H)-one derivatives in high yield in the presence of a catalytic amount of a silver salt, carbon dioxide and a base.
T. Ishida, S. Kikuchi, T. Yamada, Org. Lett., 2013, 15, 3710-3713.

An efficient one-pot regioselective ring-expansion reaction of isatins with in situ generated α-aryl/heteroaryldiazomethanes enables the construction of viridicatin alkaloids under metal-free conditions, including the naturally occurring viridicatin, viridicatol, and substituted 3-O-methyl viridicatin.
Y. Tangella, K. L. Manasa, N. H. Krishna, B. Sridhar, A. Kamal, B. N. Babu, Org. Lett., 2018, 20, 3639-3642.


A regioselective deoxygenative C-H functionalization of readily available quinoline-N-oxides with thiourea upon activation with triflic anhydride enable the synthesis of quinoline-2-thiones in very good yields.
D. I. Bugaenko, O. A. Tikhanova, A. V. Karchava, J. Org. Chem., 2023, 88, 1018-1023.