Cu(i)-catalyzed annulation for the synthesis of substituted naphthalenes using o-bromobenzaldehydes and β-ketoesters as substrates

Cu(i)-catalyzed reaction of o-bromobenzaldehydes with β-ketoesters using Cs₂CO₃ as a base and 2-picolinic acid as an additive proceeds under mild conditions and gives access to substituted naphthalenes in a single step with yields ranging from 71 to 86%. The new annulation process relies on a domino Knoevenagel condensation/C-arylation/1,2-addition/carboxylic acid cleavage. The annulation can also be achieved with o-iodobenzaldehyde.