CuSO₄–Glucose for in Situ Generation of Controlled Cu(I)–Cu(II) Bicatalysts: Multicomponent Reaction of Heterocyclic Azine and Aldehyde with Alkyne, and Cycloisomerization toward Synthesis of N-Fused Imidazoles

The catalytic efficiency of mixed Cu(I)-Cu(II) system in situ generated by partial reduction of CuSO(4) with glucose in ethanol (nonanhydrous) under open air has been explored. With this catalysis, the multicomponent cascade reaction of A(3)-coupling of heterocyclic amidine with aldehyde and alkyne, 5-exo-dig cycloisomerization, and prototropic shift has afforded an efficient and eco-friendly synthesis of therapeutically important versatile N-fused imidazoles. Diverse heterocyclic amidines, several of which are known to be poorly reactive, and aldehydes are compatible in this catalytic process.