Rhodium-Catalyzed Asymmetric Arylation-Induced Glycolate Aldol Additions of Silyl Glyoxylates

(Diene)Rh(I) complexes catalyze the stereoselective three-component coupling of silyl glyoxylates, arylboronic acids, and aldehydes to give glycolate aldol products. The participation of Rh-alkoxides in the requisite Brook rearrangement was established through two component Rh-catalyzed couplings of silyl glyoxylates with ArB(OH)2 to give silyl-protected mandelate derivatives. The intermediacy of a chiral Rh-enolate was inferred through enantioselective protonation using a chiral Rh-catalyst. Diastereoselective three-component couplings with aldehydes as terminating electrophiles to give racemic products were best achieved with a bulky aryl ester on the silyl glyoxylate reagent. Optimal enantioselective couplings were carried out with the tert-butyl ester variant using an anisole-derived enantiopure tricyclo[3.2.2.02,4]nonadiene ligand. A chiral (diene)Rh(I) complex catalyzes the enantioselective three-component coupling reaction of silyl glyoxylates, boronic acids, and aldehydes to yield complex fully substituted mandelates. Notable features include the mild generation of chiral Rh-enolates by 1,2-Brook rearrangement and, from that point, modular preparation of glycolate aldol adducts.image

Automated summary

Rhodium complexes catalyze the three-component coupling reaction, producing products with stereochemical diversity. The involvement of Rh-alkoxides in the Brook rearrangement has been confirmed. Furthermore, enantioselective products were obtained using chiral Rh-catalysts, with the best selectivity achieved using a specific ligand. The results of this study are of great significance for the synthesis of complex organic compounds.