Triphenyl verdazyl radicals’ reactivity with alkyne carboxylates as a synthetic route to 1-(phenyldiazenyl)isoquinoline-3,4-dicarboxylates

A series of 1-(phenyldiazenyl)isoquinoline-3,4-dicarboxylates are synthesized by a unique reaction of triphenyl verdazyl radical with di-substituted electron deficient alkyne carboxylates. This transformation allows for the quick synthesis of this class of compounds in just three steps starting from a hydrazone. A radical mechanism that is consistent for the substitution patterns observed in the series of compounds made is proposed. The final product is obtained by a subsequent retro-Diels–Alder reaction.