6533b861fe1ef96bd12c41f0

RESEARCH PRODUCT

Selective homogeneous hydrogenation of cycloocta-1,5, and cycloocta-1,3-diene to cyclooctene in the presence of (η4-cycloocta-1,5-diene)(η6-cycloocta-1,3,5-triene)ruthenium(0)

subject

description

Cyclooctadiene isomers (1,3- and 1,5-COD) are selectively, homogenously hydrogenated to cyclooctene (C8H14) in tetrahydrofuran (THF) solution, under mild conditions of temperature (20 °C) and hydrogen pressure (1 atm), in the presence of catalytic amounts of (cycloocta-1,5-diene)(cycloocta-1,3,5,-triene)ruthenium(0), [Ru(η4-COD)(η6-C8H10)] (1). The rate of hydrogenation is higher when 1,3-COD is the substrate. Evidence for the isomerization 1,5-COD → 1,3-COD is reported. Similar studies carried out in several alcoholic solutions, although showing a decreased selectivity in the hydrogenation, confirm the isomerization 1,5-COD → 1,3-COD, and allow a discrimination between the isomerization and the hydrogenation. The nature of the alcohol strongly influences the isomerization process, to a lesser extent the hydrogenation process. Isomerization appears to be a necessary step for the catalytic hydrogenation of 1,5-COD, in the presence of 1. Indeed, a non-isomerizable diene (bicyclo[2,2,1] hepta-2,5-diene, norbornadiene (NBD)) is not hydrogenated in the above experimental conditions. These results elucidate the mechanism of previously reported catalytic hydrogenation of conjugated trienes in the presence of 1.