Rhodium-catalysed alkoxylation/acetalization of diazo compounds: one-step synthesis of highly functionalised quaternary carbon centres.

An intermolecular tandem reaction for the rapid build-up of densely functionalised α-alkoxy-β-oxo-esters has been developed. This novel process applies the easy to handle trimethyl orthoformate as a C1-building block in the rhodium(II)-catalysed alkoxylation/acetalization of donor-acceptor substituted diazo compounds. The concomitant C-O/C-C bond formation reaction gives products with unique quaternary carbon centers, substituted by groups of different oxidation level (ester, protected aldehyde and alkoxide).