Cationic cobalt(I) catalysts for the asymmetric cyclocarbonylation of 1,6-enynes.
Cobalt(I) complexes, modified with (R)-(6,6'-dimethoxybiphenyl-2,2'-diyl)bis(diphenylphosphine) [Co((R)-MeO-Biphep)(CO)3]X (X = BF4 [1] or OTf [2]), were synthesized and characterized. The compounds have a trigonal bipyramidal structure and are fluxional. They were tested as catalyst precursors for the enantioselective cyclocarbonylation of 4,4-bis(carboethoxy)hept-5-en-1-yne 3. Enantioselectivities up to 78.5% were attained. However, activity and stereoselectivity are lower compared to catalytic systems based on Co2(CO)8 modified with the same atropisomeric ligand.
Schmid
Thomas M
TM
Institut für Chemie und Bioingenieurwissenschaften, Eidgenössische Technische Hochschule, Hönggerberg, CH-8093 Zürich, Switzerland.
Gischig
Sebastian
S
Consiglio
Giambattista
G