Continuous-flow rhodium-catalysed hydroformylation of long chain alkenes has been achieved with selectivities to the desired linear aldehyde of 92% and minimum rhodium loss, using a xantphos-derived ligand attached to an imidazolium salt in a supercritical fluid–ionic liquid system. The effect of oxygen in the system can be ameliorated to some extent by adding a simple sulfonated triphenylphosphine to the catalytic solution. [ABSTRACT FROM AUTHOR]
Phosphorus-containing multiple-bond systems have received great interest in various applications but often require elaborate syntheses and special precursors. In this paper, we describe simple methods for the synthesis of imidazoyl phosphinidenes and bis(imidazolyl)-P(I) halides from elemental phosphorus or the heptaphosphides Na3P7 and (Me3Si)3P7. The reactions of imidazolium salts with KO tBu and P4 afford mixtures of imidazoyl phosphinidenes and P n compounds and, for N-methylated imidazolium salts, also bis(imidazolyl)-P(I) halides. NMR spectroscopy studies revealed the formation of a bis(imidazoyl)-substituted tetraphosphatriene and the bicyclic anion HP4- as transient intermediates and indicated the participation of tBuOH in the formation of imidazoyl phosphinidenes. Na3P7 and (Me3Si)3P7 can be obtained from P4 and Pred in excellent yields by a safe and simple method and are versatile precursors for the synthesis of imidazoyl phosphinidenes with varying steric demand. [ABSTRACT FROM AUTHOR]
In this paper, we present the synthesis of 3-alkenylimidazo[1,2- A]pyridines in high to moderate yields by microwave direct palladium-catalyzed C-H alkenylation between bromoalkenes and imidazo[1,2- A]pyridines. The scope and limitation of the palladium(0)-catalyzed alkenylation method were investigated. Optimized conditions were successfully applied to a wide variety of imidazo[1,2- A]pyridine derivatives and bromoalkenes. The compatibility of the synthesis with the presence of a chloro substituent in the 6-position was investigated. The 6-chloroimidazo[1,2- A]pyridines were functionalized using Suzuki cross-coupling conditions to give polyfunctional compounds. [ABSTRACT FROM AUTHOR]