Asymmetric Conjugate Reductions of Coumarins. A New Route to Tolterodine and Related Coumarin Derivatives

The combination of catalytic amounts of [(R)-DTBM-SEGPHOS]CuH in the presence of stoichlometric DEMS (diethoxymethylsilane) In toluene at room temperature leads to asymmetric reductions of 4-substituted coumarins. Several targets or their known precursors can be prepared in high yields and ee's, including the muscarine receptor antagonist (R)-tolterodine.