Synthesis of 2-quinolones
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.
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 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.
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.
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.