Synthesis of dimethyl heterocyclic‐ o ‐dicarboxylates using dimethyl acetylenedicarboxylate

Dimethyl acetylenedicarboxylate (DMAD) is a very important and useful reagent for the preparation of dimethyl heterocyclic‐ o ‐dicarboxylates, which are key intermediates in the synthesis of fused pyridazine derivatives. The synthesis of thiopyranes by the Diels‐Alder reaction of dithiocarboxylate derivatives, synthesis of various cyclazines by [2 + 8] cycloaddition reactions, and synthesis of dimethyl pyrazolo[3,4‐ b ]pyridine‐5,6‐dicarboxylates and polycyclic heterocycles containing the 1,6‐naphthyridine ring system by the reaction of o ‐aminonitrile compounds with DMAD are described here.