Synthesis of Forms of a Chiral Ruthenium Complex Containing a Ru-C(sp) Bond and Their Application to Catalytic Asymmetric Cyclopropanation Reactions.

Organometallic complexes [Ru-C(sp)-Ru(II)-Pheox ] containing a Ru-C(sp) bond have been prepared from unsaturated chiral oxazoline derivatives and evaluated for asymmetric cyclopropanation reactions. The corresponding optically active cyclopropanes were obtained with high yields and high stereoselectivities (≥99/<1 /, 99% ee). The enantioselectivities were found to be affected by the geminal substituent on the Ru-C(sp) bond. In particular, Ru(II)-Prox catalyst , in which there was no geminal substituent on the metal, was shown to have the highest enantioselectivities.