Coupling Reactions of Anhydro-Aldose Tosylhydrazones with Boronic Acids

A catalyst-free coupling reaction between -peracetylated, -perbenzoylated, -permethylated, and -permethoxymethylated 2,6-anhydro-aldose tosylhydrazones ( -(β-d-glycopyranosyl)formaldehyde tosylhydrazones) and aromatic boronic acids is reported. The base-promoted reaction is operationally simple and exhibits a broad substrate scope. The main products in most of the transformations were open-chain 1- -aryl-hept-1-enitol type compounds while the expected β-d-glycopyranosylmethyl arenes (benzyl -glycosides) were formed in subordinate yields only. A mechanistic rationale is provided to explain how a complex substrate may change the well-established course of the reaction.