Erbium(III) triflate is a powerfulcatalyst for the acylation of alcohols and phenols. The reaction works well for a large variety of simple and functionalized substrates by using different kinds of acidicanhydrides Ac2O, (EtCO)2O, [(CH3)3CO]2O, Bz2O, and (CF3CO)2O} without isomerisation of chiral centres. Moreover, the catalyst can be easily recycled and reused without significant loss of activity
Porphyrins with exocyclic rings. Part 12. Synthesis of meso,β-butano- and meso,β-pentanoporphyrins from cycloalka[b]pyrroles
作者:Jolie A. Bastian、Timothy D. Lash
DOI:10.1016/s0040-4020(98)00327-5
日期:1998.6
Knorr-type condensations with cycloheptanone or cyclooctanone, respectively. Treatment with lead tetraacetate in dichloromethane afforded the labile ω-acetates 8 and subsequent acid catalyzed condensation with α-unsubstituted pyrrole-2-carboxylates yielded the related pyrrolylcycloalka[b]pyrroles 29 and 30. The α-unsubstituted pyrroles 14 and 23 were prepared by condensing α,β-unsubstituted ketones, or their
[GRAPHICS]Nonactivated hydrocarbon sites of enantiopure compounds are oxyfunctionalized enantiospecifically by perfluoro-cis-2-n-butyl-3-n-propyloxaziridine under remarkably mild reaction conditions. The reaction occurs with retention of configuration at the oxidized stereogenic center, and the enantiospecificity is highly independent from both the carbon framework of the substrate and the presence of functional groups.