Mikami Koichi, Kataoka Shohei, Yusa Yukinori, Aikawa Kohsuke
Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-8552, Japan.
Org Lett. 2004 Oct 14;6(21):3699-701. doi: 10.1021/ol048604l.
[reaction: see text] The tropos (chirally flexible) or atropos (chirally rigid) nature of BIPHEP-Rh complexes at room temperature critically depends on the amines complexed. The aliphatic DPEN complex is atropos, whereas the aromatic DABN complex is tropos. BIPHEP-Rh chirality can thus be controlled by DABN at room temperature. The amine-free BIPHEP-Rh complex is tropos. At 5 degrees C, even amine-free BIPHEP-Rh complexes are atropos and hence can be used as enantiopure catalysts to give high enantioselectivity in ene-type cyclization of 1,6-enynes.
