Ni-Catalyzed Asymmetric Cycloisomerization of Dienes by Using TADDOL Phosphoramidites

A library of α,α,α,α-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based phosphoramidites has been synthesized and applied in the Ni-catalyzed cycloisomerization of different dienes. Through the systematic variation of the three structural motifs of the lead structure, that is, the amine moiety, the protecting group, and the aryl substituents, the ligand features could be optimized for the asymmetric cycloisomerization of the model substrate diethyl diallylmalonate. The substrate scope of the new catalytic system was extended to other diallylic substrates, including unsymmetrical dienes. Overall remarkably high activities of up to approximately 13 500 h(-1) , very high selectivities toward five-membered exo-methylenecyclopentanes, and enantioselectivities of up to 92 % ee have been achieved.