Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to Coumarins:  Asymmetric Synthesis of (R)-Tolterodine

[reaction: see text]. Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins proceeded with high enantioselectivity in the presence of a rhodium catalyst (3 mol %) generated from Rh(acac)(C2H4)2 and (R)-Segphos to give the corresponding (R)-4-arylchroman-2-ones in over 99% ee. This asymmetric reaction was applied to the synthesis of (R)-tolterodine.