Three-Component Coupling of Aromatic Aldehydes, 1-Morpholino-2-nitroalkenes, and 3-Aminoazoles via Boron Trifluoride Etherate Catalysis: Reaction Pathway and Features of the Formation of Intermediates.

4,7-Dihydro-6-nitro-7-Ar-5--azolo[1,5-]pyrimidines were obtained by the multicomponent reaction of aminoazoles, morpholino-nitroalkenes, and aromatic aldehydes in the catalysis of boron trifluoride etherate. The optimal reaction conditions were determined, and the formation of the target regioisomer was demonstrated. The pathway for multicomponent transformation, including the formation of azolyl-nitroalkene, was determined. Morpholino-nitroalkenes were assumed to convert into the corresponding nitroalkynes during catalysis of boron trifluoride etherate. For a multicomponent reaction with 4-nitrobenzaldehyde, conditions have been proposed that exclude the formation of a side regioisomer.