Asymmetric dearomatization of the furan ring promoted by conjugate organolithium addition to (menthyloxy)(3-furyl)carbene complexes of chromium.
The sequential low-temperature addition reaction of an organolithium compound and methyl triflate to (menthyloxy)(3-furyl)carbene complexes of chromium and tungsten proceeded with excellent regioselectivity (1,4-addition) and diastereoselectivity (2,3-trans disposition of the nucleophile and electrophile groups) to afford new 2,3-disubstituted (2,3-dihydro-3-furyl)carbene complexes. In addition, a high degree of diastereofacial selectivity was achieved by employing alkenyllithium compounds. After detachment of both the metal fragment and the chiral auxiliary group, trisubstituted 2,3-dihydrofuran derivatives containing a quaternary stereogenic center at the C3 position were obtained. The characterization, including X-ray crystallography, of a novel type of stable four-membered chelate (eta(2)-alkene)tetracarbonylcarbene complex of chromium is also reported.
Barluenga
José
J
Instituto Universitario de Química Organometálica Enrique Moles, Unidad Asociada al CSIC, Universidad de Oviedo, Julián Clavería 8, 33006 Oviedo, Spain. barluenga@sauron.quimica.uniovi.es
Nandy
Sandip K
SK
Laxmi
Y R Santosh
YR
Suárez
José Ramón
JR
Merino
Isabel
I
Flórez
Josefa
J
García-Granda
Santiago
S
Montejo-Bernardo
José
J