Synthesis of δ-lactams
A quick, efficient, one-pot, BF3ˇOEt2-mediated reaction of various substituted arenes with azido alkanoic acid chlorides affords substituted N-aryl lactams in good to excellent yields at room temperature.
D. Caturvedi, A. K. Chaturvedi, N. Mishra, V. Mishra, Synlett, 2012, 23, 2627-2630.
An Al(OTf)3-catalyzed cascade cyclization and ionic hydrogenation reaction of nitrogen substituted ketoamides enables an efficient and versatile synthesis of N-substituted lactams, pyrrolindinones, piperidones, and structurally related heterocycles in good yields.
J. Qi, C. Sun, Y. Tian, X. Wang, G. Li, Q. Xiao, D. Yin, Org. Lett., 2014, 16, 190-192.
Ir catalysis achieves a lactam synthesis directly from lactones and amines via aminolysis of lactone, N-alkylation of amine with hydroxyamide, and intramolecular transamidation of aminoamide.
K. Kim, S. H. Hong, J. Org. Chem., 2015, 80, 4152-4156.
In a metal-free, selective oxidation of cyclic secondary and tertiary amines for the formation of lactams, molecular iodine facilitates both chemoselective and regioselective oxidation of C-H bonds directly adjacent to a cyclic amine. The reaction offers mild conditions, functional group tolerance, and a broad substrate scope.
R. J. Griffiths, G. A. Burley, E. P. A. Talbot, Org. Lett., 2017, 19, 870-873.
A palladium-catalyzed intramolecular hydroamidation of amidoalkynes in 1,4-dioxane at 100°C gives lactams in good yields.
N. T. Patil, Z. Huo, G. B. Bajracharya, Y. Yamamoto, J. Org. Chem., 2006, 71, 3612-3614.
Alkylation of the aza-enolate of valerolactim methyl ether with electrophiles affords α-alkyl lactims. Subsequent mild, acidic hydrolysation gives the corresponding α-alkyl-δ-amino esters hydrochloride salts. Neutralisation of these salts with base results in smooth intramolecular cyclisation to afford α-alkyl lactams in excellent yield.
P. J. M. Taylor, S. D. Bull, P. C. Andrews, Synlett, 2006, 1347-1350.
A very efficient NHC-catalyzed ring expansion reaction cleanly furnishes five- and six-membered N-Ts and N-Bn lactams, without the need for further purification. The stoichiometric base is responsible for deprotonation of the triazolium precatalyst and activation of the nitrogen leaving group through hydrogen bonding.
K. Thai, L. Wang, T. Dudding, F. Bilodeau, M. Gravel, Org. Lett., 2010, 12, 5708-5711.
N-Alkenyl β-ketoamides undergo a mild cyclization in the presence of Au[P(t-Bu)2(o-biphenyl)]Cl and AgOTf with excellent regioselectivities and yields. The reaction provides an efficient method to prepare highly substituted lactams.
C.-Y. Zhou, C.-M. Che, J. Am. Chem. Soc., 2007, 129, 5828-5829.
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.
An intramolecular vinylation of various iodoenamides using CuI as the catalyst and N,N'-dimethylethylenediamine as the ligand led to five- to seven-membered lactams in moderate to excellent yields.
T. Hu, C. Li, Org. Lett., 2005, 7, 2035-2038.
A direct Pd-catalyzed arylation reaction for the intramolecular formation of biaryl compounds using a novel phosphine ligand offers enhanced catalytic activity for transformations of previously unreactive substrates.
L.-C. Campeau, M. Parisien, M. Leblanc, K. Fagnou, J. Am. Chem. Soc., 2004, 126, 9186-9187.