Palladium-catalyzed telomerization of butadiene with ethylene glycol in liquid single phase and biphasic systems: control of selectivity and catalyst recycling

The palladium-catalyzed telomerization of 1,3-butadiene (Bu) with ethylene gylcol (EG) has been studied in liquid single phase and aqueous biphasic systems. All important parameters have been examined, including temperature, catalyst system, catalyst concentration, Bu/EG ratio, P/Pd ratio, solvent and reaction time. In homogeneous phase mixtures of 2-(2,7-octadienyloxy)ethanol (1a) and 2-(1-ethenyl-5-hexenyloxy)ethanol (1b) were formed in yields up to 60%, but also ditelomers (2) and butadiene dimers (3) were produced in significant amounts. In aqueous biphasic systems, however, using a palladium catalyst with the triphenylphosphinetrisulfonate (TPPTS) ligand, the monotelomers 1a and 1b were obtained in 80% yield with more than 95% selectivity. A mechanism is proposed explaining the observed differences in selectivity. The aqueous catalyst phase could be recycled six times resulting only in a slight decrease of activity. The products 1a and 1b were hydrogenated in quantitative yield to the corresponding saturated compounds 2-octyloxyethanol (6a) and 2-(1-ethyl-hexyloxy)ethanol (6b) using a Pd/Al2O3 catalyst under mild conditions. The products can be used for a variety of applications like plasticizers, cosmetics and solvents. (C) 2002 Elsevier Science B.V. All rights reserved.