Niobium(V) chloride-catalyzed C–H insertion reactions of α-diazoesters: synthesis of β-keto esters

Aldehydes react readily with ethyl diazoacetate in the presence of 5 mol% of NbCl5 in dichloromethane to produce the corresponding β-keto esters in good yields with high selectivity. This method is very useful for the preparation of β-keto esters from both electron-rich as well as electron-deficient aromatic aldehydes under mild reaction conditions.