Vilsmeier–Haack reactions of carbonyl compounds: synthesis of substituted pyrones and pyridines

Vilsmeier–Haack reaction of substituted phenylacetones leads to the formation of conjugated iminium salts which on aqueous basic work up afford 3-formyl-4-pyrones and on ammonium acetate-induced cyclization afford 5-aryl-4-chloronicotinaldehydes in good yields.