Improved Arndt−Eistert Synthesis of α-Diazoketones Requiring Minimal Diazomethane in the Presence of Calcium Oxide as Acid Scavenger

A practical methodology to obtain α-diazoketones through an improved Arndt−Eistert synthesis is described. The method allows the efficient transformation of acid halides using a stoichiometric amount of diazomethane in the presence of calcium oxide, without concomitant ketene or haloketone formation. The obtained α′-brominated-α-diazoketones were employed as suitable substrates for the synthesis of interesting α-arylamino-α′-halomethylketones.