α-Diazo-β-dicarbonyl compounds were chlorinated using (dichloro)iodobenzene and an
activating catalyst. A broad range of reaction rates was observed, which paralleled
the relative stability/nucleophilicity of the diazo compounds. Acyclic diazocarbonyls
reacted faster than cyclics, and β-diketones were much faster to react than β-keto
esters or β-diesters. Lewis acid activation was used for the first time, allowing
us to overcome instances of poor chemoselectivity. Though the yields ranged from low
to good, this chlorination reaction has again proven a mild and effective halogenation
strategy.
Key words
diazo compounds - hypervalent iodine - halogenation - catalysis - ylides