RESUMO
The alkylation of amines by alcohols has been achieved using 0.5 mol % [Ru(p-cymene)Cl(2)](2) with the bidentate phosphines dppf or DPEphos as the catalyst. Primary amines have been converted into secondary amines, and secondary amines into tertiary amines, including the syntheses of Piribedil, Tripelennamine, and Chlorpheniramine. N-Heterocyclization reactions of primary amines are reported, as well as alkylation reactions of primary sulfonamides. Secondary alcohols require more forcing conditions than primary alcohols but are still effective alkylating agents in the presence of this catalyst.
Assuntos
Aminas/síntese química , Sulfonamidas/síntese química , Álcoois/química , Alquilação , Aminas/química , Catálise , Cimenos , Compostos Organometálicos/química , Sulfonamidas/químicaRESUMO
Phosphine modified rhodium complexes are currently the topic of considerable research as methanol carbonylation catalysts, but often suffer from poor stability. This paper reports on an investigation into how coordination mode affects the elimination of phosphonium salts from rhodium complexes, namely [trans-RhCl(CO)(PPh3)2] 1, [RhCl(CO)(dppe)] 2, [RhCl(CO)(dppb)]2 3, [Rh(TRIPHOS)(CO)2]Cl 4. These complexes are all potential pre-catalysts for methanol carbonylation. The reaction of these complexes with methyl iodide at 140 degrees C under both N2 and CO atmospheres has been studied and has revealed clear differences in the stability of the corresponding Rh(III) complexes. In contrast to both monomeric 2 and dimeric 3 that react cleanly with CH3I to give stable Rh(III) acetyl complexes, 4 forms a novel bidentate complex after the elimination of the one arm of the ligand as a quaternised phosphonium salt. The structure of this complex has been determined spectroscopically and using X-ray crystallography. The mechanism of formation of this novel complex has been investigated using 13CH3I and strong evidence that supports a dissociative mechanism as the means of phosphine loss from the rhodium centre is provided.