Rhodium(I)-catalyzed enantioselective activation of cyclobutanols: formation of cyclohexane derivatives with quaternary stereogenic centers.
The activation of carbon-carbon sigma bonds is a complementary method to access uncommon and difficult-to-prepare organometallic species. Herein, we describe the activation of tert-cyclobutanols through an enantioselective insertion of a chiral rhodium(I) complex into the C-C sigma bond of the cyclobutane, forming a quaternary stereogenic center and an alkyl-rhodium functionality that initiates ring-closure reactions. This technology provides access to a variety of substituted cyclohexane derivatives with quaternary stereogenic centers. The formation of different product families can be controlled by the employed set of reaction conditions and additives. In general, high yields and excellent enantioselectivities of up to 99% ee are obtained.
ETH Zurich, Laboratory of Organic Chemistry, HCI H 304, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland.
Tobias
T
Seiser
Nicolai
N
Cramer