Single-Step Construction of Planar and Central Chirality in Metallocenes by Rhodium-Catalyzed Desymmetric Cyclization

One-step asymmetric synthesis of metallocenes with planar and central chirality was developed by rhodium-catalyzed desymmetric cyclization. The reactions of prochiral 1,2-dialkenyl metallocenes with organoboronic acids were carried out in dioxane at 25 ? in the presence of an Rh/(S,S)-Fc-tfb complex. Metallocenes, having one chiral plane and three chiral centers, were obtained in high yields with excellent diastereo- and enantioselectivity (>50:1 dr, up to >99.5% ee). Mechanistic studies have shown the reactions proceed through a desymmetric conjugate addition-Michael cyclization sequence. Both planar chirality and the first central chirality are constructed simultaneously in a single desymmetric addition step. The synthetic utility is demonstrated by the asymmetric synthesis of a novel chiral chain diene ligand, self-replication of which was successfully achieved.

Automated summary

One-step asymmetric synthesis of metallocenes with planar and central chirality was achieved using rhodium catalysis. The reactions proceeded through a desymmetric conjugate addition-Michael cyclization sequence, allowing for the simultaneous construction of both planar and central chirality. The synthetic utility of this method was demonstrated by the asymmetric synthesis of a novel chiral chain diene ligand.