32668-78-3Relevant articles and documents
Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst
Ryabchuk, Pavel,Leischner, Thomas,Kreyenschulte, Carsten,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
supporting information, p. 18679 - 18685 (2020/09/02)
A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO2-L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal–Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H2O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane.
Enantiomers and Barriers to Racemization of Sterically Hindered N-Aryl- and N-Heteroarylpyrroles
Vorkapic-Furac, Jasna,Mintas, Mladen,Kastner, Fritz,Mannschreck, Albrecht
, p. 327 - 333 (2007/10/02)
The N-aryl- and N-heteroaryl-2,5-dimethylpyrrole-3-carbaldehydes 2-8 have been synthesized by condensation of hexane-2,5-dione with the appropriate amine and subsequent Vilsmeier-Haack formylation of the pyrrole ring.Diastereomeric association complexes of the racemic pyrrole 8 were studied by pmr chemical shifts and the aplittings induced by (+)-1-(9-anthryl)-2,2,2-trifluoroethanol.Enrichment of the enantiomers M and P of 2 and 6 was achieved by liquid chromatography on triacetylcellulose.The barrier to partial rotation about the C-N bond in 6 was determined by thermal racemization and its lower limits in 2 and 8 were estimated.
