<i>Tropos</i> or <i>Atropos</i> Nature of Rhodium Complexes Bearing a Tetrakis(phosphanyl)terphenyl Ligand:  Highly Enantioselective Catalysis of Ene-Type Cyclization

Abstract

[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.