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.
Institut für Chemie und Bioingenieurwissenschaften, Eidgenössische Technische Hochschule, Hönggerberg, CH-8093 Zürich, Switzerland.
Thomas M
TM
Schmid
Sebastian
S
Gischig
Giambattista
G
Consiglio