Synthesis of 3-pyrrolin-2-ones
A 3 + 2 cycloaddition of α-imino rhodium carbenoids generated from 1-sulfonyl 1,2,3-triazoles with ketene silyl acetals offers a novel and straightforward synthesis of biologically interesting 3-pyrrolin-2-ones with broad substrate scope.
R.-Q. Ran, J. He, S.-D. Xiu, K.-B. Wang, C.-Y. Li, Org. Lett., 2014, 16, 3704-3705.
Regioselective ring closing ene-yne metathesis provided an efficient access to different substituted 1-benzazepine scaffolds. Five- and six-membered lactams were efficiently prepared by ring-closing metathesis affording highly functionalizable compounds.
E. Benedetti, M. Lomazzi, F. Tibiletti, J.-P. Goddard, L. Fensterbank, M. Malacria, G. Palmisano, A. Penoni, Synthesis, 2012, 44, 3523-3533.
The common organo-photocatalyst Eosin Y shows excellent catalytic activities for thermal redox reactions under a catalytic amount of Cu(OAc)2 too. Using this catalytic system, a formal [3 + 2] cycloaddition of vinyl azides and ketene silyl acetals provides five-membered ene-γ-lactams and bridge ring lactams via an α-ester radical addition without light irradiation.
W.-L. Lei, K.-W. Feng, T. Wang, L.-Z. Wu, Q. Liu, Org. Lett., 2018, 20, 7220-7224.
Dimethyl sulfoxide (DMSO) and N-iodosuccinimide mediate a metal-free regioselective 5-exo-dig oxidative cyclization of propargyl-substituted ynamides via in situ generated enol equivalents. The reaction allows easy access to functionalized pyrrolidone skeletons. The role of DMSO as oxidant in the transformation is clarified, and a tentative reaction pathway is proposed.
B. Prabagar, S. Nayak, R. Prasad, A. K. Sahoo, Org. Lett., 2016, 18, 3066-3069.
Conventional approaches for the synthesis of tetramic acid derivatives often require highly functionalized starting materials and harsh heating conditions in basic media. A silver-catalyzed strategy enables a mild synthesis of tetramic acid derivatives from easily available propargylic amines and carbon dioxide in the presence of DBU.
T. Ishida, R. Kobayashi, T. Yamada, Org. Lett., 2014, 16, 2430-2433.