Kinetic Resolution of Planar-Chiral (η5‑Bromocyclopentadienyl)manganese(I) Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis

Kinetic resolution of racemic planar-chiral (η5-1-alkenyl-2-bromocyclopentadienyl)­manganese­(I) complexes 1 was realized by the molybdenum-catalyzed asymmetric ring-closing metathesis. While vinyl-Cp derivative 1a was resolved in excellent enantioselectivity with the krel values of up to 127, the selectivity in the ARCM reaction of allyl-Cp derivative 1b was modest (krel = 3.0). ARCM product 2a, which was obtained in an enantiomerically pure form by the two successive ARCM reactions or recrystallization of the enantiomerically enriched products, was found to be a versatile synthetic precursor to various planar-chiral cymantrene derivatives.