1294518-13-0Relevant articles and documents
A palladium(II) Center activates nitrile ligands toward 1,3-dipolar cycloaddition of nitrones substantially more than the corresponding platinum(II) center
Kritchenkov, Andreii S.,Bokach, Nadezhda A.,Starova, Galina L.,Kukushkin, Vadim Yu.
, p. 11971 - 11979,9 (2012)
Palladium(II)-coordinated NCR1 (R1 = Et (1), NMe 2 (2), Ph (3)) species react smoothly with acyclic nitrones such as the ketonitrones Ph2C=N(O)R4 (R4 = p-MeC 6H4 (4), p-ClC6H4 (5)) and the aldonitrone p-MeC6H4CH=N(O)Me (6) in the corresponding nitrile media. This reaction proceeds as a consecutive two-step intermolecular cycloaddition to give the mono- and bis-2,3-dihydro-1,2,4-oxadiazole complexes [PdCl2(R1CN){Na=C(R1)ON(R 4)Cb(R2R3)}](a-b) (7a-13a; R2, R3 = Ph; R4 = C6H 4Me-p, R1 = Et (7), NMe2 (8), Ph (9); R 4 = C6H4Cl-p, R1 = Et (10), NMe 2 (11), Ph (12); R2 = H, R3 = C 6H4Me-p, R4 = Me, R1 = NMe 2 (13)) and [PdCl2{Na=C(R1)ON(R 4)Cb(R2R3)}2] (a-b) (7b-13b), respectively. Inspection of the obtained data and their comparison with the previous results indicate that the PdII centers provide substantially greater activation of RCN ligands toward the 1,3-dipolar cycloaddition than the relevant PtII centers. The palladium(II)-mediated 1,3-dipolar cycloaddition of ketonitrones to nitriles is reversible. All complexes were characterized by elemental analyses (C, H, N), high-resolution ESI-MS, and IR and 1H and 13C{ 1H} NMR spectroscopy. The structure of trans-7b was determined by single-crystal X-ray diffraction. Metal-free 5-NR′2-2,3- dihydro-1,2,4-oxadiazoles (7c-13c) were liberated from the corresponding (2,3-dihydro-1,2,4-oxadiazole)2PdII complexes by treatment with 1,2-(diphenylphosphino)ethane, and the heterocycles were characterized by high-resolution ESI+-MS and 1H and 13C{ 1H} spectroscopy.
