Microwave-Assisted Dehydrosulfurization: An Efficient, Solvent-Free Synthesis of 5-(1-Adamantyl)-2-arylamino-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles

Abstract

A fast and efficient microwave-assisted synthesis of 2-arylamino-5-(1-adamantyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles is described. The reaction of 3-(l-adamantyl)-5-mercapto-l,2,4-triazole (2) with arylisothiocyanates in DMF at room temperature yielded the corresponding N,N'-disubstituted thioureas (3a-e) in high yields. Compounds (3a-e) were desulfurized via microwave irradiation for 5 min to yield the corresponding 5-(l-adamantyl)-2-arylamino-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles (4a-e). Compounds (4a-e) were also prepared in good yields via microwave irradiation of a mixture of (2) and the corresponding arylisothiocyanates for 8 minutes. Attempted preparation of the aliphatic analogues (6a-e) via microwave irradiation was unsuccessful, they were obtained in poor yields via prolonged heating of compound (2) with the corresponding aliphatic isothiocyanate in DMF. Compounds (6a-e) were independently obtained in good yields via the reaction of (2) with cyanogen bromide to yield the 2-amino analogue (7) that was subsequently reacted with the corresponding aliphatic halide.