Carbohydrate–metallocene conjugates: selective formation of a zirconadioxacyclopentane-type dimer from the reaction of a bis(enolate)ZrCp2 reagent with a glucofuranoside derivative

Abstract

The zirconocene enolate complex bis(2-propenolato)ZrCp₂ (1) reacts with two molar equivalents of the 1,2,3,4-O-tetramethyl-α-D-glucopyranoside (2) with liberation of two equivalents of acetone to yield cleanly the bis(carbohydrate)zirconcene complex (3). Alternatively 1 and the “bifunctional” glucose derivative 3-O-benzyl-1,2-O-isopropylidene-glucofuranoside (4) react to the corresponding zirconadioxacyclopentane-type metallacyclic product that was isolated as the respective dimer (5) featuring a sequence of linearly anellated five-, four-, five-membered metallacycles. Both carbohydrate zirconocene complexes 3 and 5 were characterized by NMR experiments as well as by X-ray diffraction.