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-typecyclization of 1,6-enynes.
Chiral aminoalcohol NOBIN for instantaneous chirality control of racemic but tropos BIPHEP–Rh(I)-complexes: highly enantioselective ene-type cyclization of 1,6-enynes catalyzed by the Rh(I)-complexes without use of acid
instantaneously even at room temperature. The BIPHEP–Rh/NOBIN complex thus controlled can be used as an asymmetric catalyst to give higher enantioselectivity (up to 98% ee) and yield in ene-typecyclization of 1,6-enynes without use of acid.