RESUMO
A rhodium complex bearing a chiral bicyclic NHC ligand, [RhCl(3az)(cod)] 4az, was synthesized and fully characterized by X-ray diffraction analysis, high-resolution mass spectrometry, and multinuclear NMR spectroscopy. The electronic and steric properties of NHC ligand 3az were evaluated by IR measurement and X-ray diffraction analysis of dicarbonyl complex [RhCl(3az)(CO)2] 5az, which was prepared by replacing the COD ligand of 4az with CO. The potential of novel complex 4az as a chiral catalyst was investigated in the Rh-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadienes with amines, and the corresponding products were afforded in good yields with good enantioselectivities (up to 81% ee).
RESUMO
The treatment of easily accessible o-(1-hydroxy-2-alkynyl)-N-tosylanilides 1 with excess manganese(IV) oxide in the presence of substoichiometric tetrabutylammonium iodide (TBAI) in chloroform (or in the absence of TBAI in dimethylformamide, DMF) promoted a sequential oxidation/intramolecular hydroamination to give 4-quinolones 3 and/or (Z)-2-alkylidene-3-oxindoles (Z)-4 in good yields. Possibly, MnO2 played dual roles as an oxidant and as a Lewis acidic activator of intermediary ynones 2. The product distributions between 3 and (Z)-4 could be controlled by the choice of solvents.
