Tropos or atropos nature of rhodium complexes bearing a tetrakis(phosphanyl)terphenyl ligand: highly enantioselective catalysis of ene-type cyclization.
[reaction and structure: see text] Not only axial but also helical chirality of tropos TETRAPHOS-Rh complexes can be controlled by chiral diamines. The flexibility of the TETRAPHOS-Rh complex is increased by association of DABN. In contrast, the diamine-free complex is chirally more stable than the BIPHEP counterpart. The higher levels of enantioselectivity in ene-type cyclization of 1,6-enynes can thus be achieved even at room temperature by the diamine-free TETRAPHOS-Rh complex.
Mikami
Koichi
K
Department of Applied Chemistry, Tokyo Institute of Technology, Tokyo 152-8552, Japan. kmikami@o.cc.titech.ac.jp
Kataoka
Shohei
S
Aikawa
Kohsuke
K