A series of bulky phosphines containing substituted biphenyl, 2-methylnaphthyl, or 2,7-di-tert-butyl-9,9-dimethylxanthene moiety were prepared. They were used in the preparation of new monophosphine−palladium(0)−dvds complexes, which were employed as catalysts for the selective telomerization of 1,3-butadiene with methanol to obtain 1-methoxyocta-2,7-diene (1-MOD), the key intermediate in the Dow 1-octene process. Several ligands showed improved selectivity and yield compared to that of the benchmark ligand PPh3. Especially 2,7-di-tert-butyl-9,9-dimethylxanthen-4-yl-diphenylphosphine (4, “mono-xantphos”) stands out as an excellent ligand in terms of yield, selectivity, and stability.
Tschan, M. J-L., Garcia, E., Freixa, Z., Launay, H., Hagen, H., Benet-Buchholz, J., & van Leeuwen, P. W. N. M. (2010). Efficient Bulky Phosphines for the Selective Telomerization of 1,3-Butadiene with Methanol. Journal of the American Chemical Society, 132(18), 6463-6473. https://doi.org/10.1021/ja100521m