Anthony George Abatjoglou

Rhodium-catalyzed low pressure hydroformylation of vinyl esters: Solvent and phosphine effects on catalyst activity, selectivity and stability

Summary Rhodium/triarylphosphine complexes catalyze the low pressure ydroformylation of vinyl esters to α- and β-carbocypropionaldehydes. In contrast with hydrocarbon α-olefins, the branched aldehydes predominate, and the regioselectivity of the reaction is virtually unaffected by carbon monoxide partial pressure. Substrate steric effects and solvent effects are significant on both the reaction rates and linear/branched aldehyde selectivities. Rhodium-promoted hydrogenolysis of vinyl esters to ethylene and carboxylic acid is a major side reaction of this process. The results are rationalized in terms of the ability of the vinyl esters to form chelates.

Carbonylation of methanol at unusually low temperature and pressure with cis-RhCl(CO)2Ph2P(CH2)2P(O)Ph2

cis-RhCl(CO)2Ph2P(CH2)2P(O) Ph2, the only species observed during catalysis, formed from cis-[graphic omitted])Ph2 and CO, is the sole active species observed during catalytic studies and results in the carbonylation of methanol with catalyst turnover frequencies approaching 400 h–1 at 80 °C and 50 psig CO; the crystal structure of the analogue cis-[graphic omitted])Ph2 is reported.

Direct NMR observation of atropisomerism of a bisphosphite dibenzo[d,f][1,3,2]dioxaphosphepin moiety

Rapid interconversion of two diastereoisomeric bisphosphite ligands by dibenzo[d,f][1,3,2]dioxaphosphepin epimerization has been observed by variable temperature 1H NMR.