Asymmetric catalysis of Nozaki-Hiyama allylation and methallylation with a new tridentate bis(oxazolinyl)carbazole ligand

This work describes the development of a new tridentate ligand effective for the asymmetric catalysis of Nozaki-Hiyama allylation and methallylation. Various aldehydes were allylated or methallylated with good enantioselectivity (86-96%), and a key intermediate of calcitriol lactone synthesis was also obtained with excellent diastereoselectivity (97% de, 91%). The enantioselective reaction catalyzed by this Cr-ligand complex is applicable to a broad range of aldehydes and has great potential for natural product synthesis. Another remarkable feature of this ligand is the stability of the Cr-ligand complex which was recovered after the enantioselective reaction and recycled twice without diminishing the enantioselectivity and yield.