Abstract A series of 5-substituted-2-(4-alkyl or phenyl-1, 2, 3-thia (or selena) diazol-5-yl)-1, 3, 4-oxadiazoles were prepared. 5-Substituted-2-(4-phenyl-1, 2, 3-selenadiazol-5-yl)-1, 3, 4- oxadiazoles upon pyrolysis afforded the corresponding alkynes. Also, a series of 5- substituted-4-amino-3-(1, 2, 3-thiadiazol-5-yl)-s-triazoles and 5-(1, 2, 3-thiadiazolyl)-s- triazolo [3, 4-b]-1, 3, 4-thiadiazoles were prepared.