Synthesis of γ-lactams
An oxidative copper-catalyzed arylation of various ring-size lactams with arylboronic acids gives N-arylated products in good yield without any additional bases, ligands, or additives.
T. Bathini, V. S. Rawat, B. Sreedhar, Synlett, 2015, 26, 1348-1351.
A quick, efficient, one-pot, BF3·OEt2-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.
A gold-catalyzed tandem cycloisomerization/oxidation of homopropargyl amides provides ready access to synthetically useful chiral γ-lactams with excellent ee by combining the chiral tert-butylsulfinimine chemistry and gold catalysis. The use of readily available starting materials, a simple procedure, and mild reaction conditions are other significant features of this method.
C. Shu, M.-Q. Liu, S.-S. Wang, L. Li, L.-W. Ye, J. Org. Chem., 2013, 78, 3292-3299.
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.
Concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex enables amide activation in the presence of a weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. The thiophenol cocatalyst furnishes the product and regenerate the active forms of the photocatalyst.
D. C. Miller, G. J. Choi, H. S. Orbe, R. R. Knowles, J. Am. Chem. Soc., 2015, 137, 13492-13495.
Addition of amide enolates to acylsilanes generates β-silyloxy homoenolates by undergoing a 1,2-Brook rearrangement. These unique nucleophiles formed in situ can then undergo addition to alkyl halides, aldehydes, ketones, and imines. γ-Amino-β-hydroxy amide products derived from a diastereoselective addition to N-diphenylphosphinyl imines can be efficiently converted to γ-lactams.
R. B. Lettan, II, C. V. Galliford, C. C. Woodward, K. A. Scheidt, J. Am. Chem. Soc., 2009, 131, 8805-8814.
A highly diastereoselective reaction of 2,5-bis(trimethysilyloxy)furan with imines gives β-carboxy-γ-lactams and their ethyl ester derivatives in high yields via a Mukaiyama-aldol type reaction with high diastereomeric ratio employing Sc(OTf)3 as catalyst.
M. Pohmakotr, N. Yotapan, P. Tuchinda, C. Kuhakarn, V. Reutrakul, J. Org. Chem., 2007, 72, 5016-5019.
The hypervalent iodine reagent PIFA promotes the efficient intramolecular electrophilic cyclization of easily accessible alkynylamides and alkynyl carboxylic acids, leading to pyrrolidinone and lactone skeletons, respectively. A synthetic study and a mechanistic proposal for these transformations are presented.
I. Tellitu, S. Serna, M. T. Herrero, I. Moreno, E. Domínguez, R. SanMartin, J. Org. Chem., 2007, 72, 1526-1529.
The utility of a Design of Experiments (DoE) approach for the rapid and efficient optimisation of a microwave assisted Ugi 3cc reaction of levulinic acid with a range of amine and isonitrile substrates has enabled the preparation of lactam derivatives in moderate to excellent yields in a reaction time of only 30 min compared to the conventional methodology which required up to 48 h.
H. Tye, M. Whittaker, Org. Biomol. Chem., 2004, 2, 813-815.
The reaction of amide and thioamide dianions with epibromohydrin resulted in regioselective formation of 5-(hydroxymethyl)pyrrolidin-2-ones (pyroglutaminols) and -thiones.
I. Freifeld, H. Armbrust, P. Langer, Synthesis, 2006, 1807-1808.
Under selected conditions, the Zr-catalyzed reaction of EtMgCl with imines produces C,N-dimagnesiated compounds, which can be further trapped with electrophiles. The overall transformation provides a new route to bifunctional or cyclic nitrogen-containing compounds such as 1-azaspirocyclic γ-lactams, pyrrolidines and azetidines.
V. Gandon, P. Bertus, J. Szymoniak, Synthesis, 2002, 1115-1120.
Several Pd-catalyzed oxidative cyclizations proceed in excellent yield under simple aerobic conditions. Importantly, this system provided entry into enatioselective catalysis with a readily available Pd-sparteine complex.
R. M. Trend, Y. K. Ramtohul, E. M. Ferreira, B. Stoltz, Angew. Chem. Int. Ed., 2003, 42, 2892-2895.
A convenient and highly regioselective method allows the synthesis of 5-methylenepyrrolidinone derivatives from various nitriles and acrylamides via a cobalt-catalyzed reductive coupling reaction. A possible mechanism involves the formation of a cobaltaazacyclopentene intermediate from nitrile and acrylamide, protonation, keto-amide cyclization, and dehydration.
Y.-C. Wong, K. Parthsarathy, C.-H. Cheng, J. Am. Chem. Soc., 2009, 131, 18252-18253.
Catalytic hydrogenation of acetylenic aldehydes using a chirally modified cationic rhodium catalysts enables highly enantioselective reductive cyclization to afford cyclic allylic alcohols. Using an achiral hydrogenation catalyst, some chiral racemic acetylenic aldehydes engage in highly syn-diastereoselective reductive cyclizations.
J. U. Rhee, M. J. Krische, J. Am. Chem. Soc., 2006, 128, 10674-10675.
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.
Preferential Rh(II) carbenoid intramolecular C-H versus O-H insertion derived from α-diazo-acetamides can be achieved in water by creating a large hydrophobic environment around the reactive carbenoid center using an appropriate combination of the catalyst and amide groups.
N. R. Candeias, P. M. P. Gois, C. A. M. Afonso, J. Org. Chem., 2006, 71, 5489-5497.
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 new Pd-catalyzed oxidation reaction for the stereospecific conversion of enynes into cyclopropyl ketones proceeds with net inversion of geometry with respect to the starting olefin. This result is consistent with a mechanism in which the key cyclopropane-forming step involves nucleophilic attack of a tethered olefin onto the PdIV-C bond.
L. L. Welbes, T. W. Lyons, K. A. Cychosz, M. S. Sanford, J. Am. Chem. Soc., 2007, 129, 5836-5837.