5-(p-Tolyl)-2-[(p-tolylethylidene)hydrazino] thiazole (3) and 3-[(p-tolylethylidene )amino]-2-thiohydantoin (6) have been prepared via cyclization of p-methyl acetophenone thiosemicarbazone (2) with p-methylphenacyl bromide and ethyl chloroacetate in presence of fused sodium acetate . Acetylation of 2,3 and 6 with acetic anhydride afforded the corresponding diacetyl derivative(5) and mono acetyl derivatives (4 and 7). Reaction of 2-thiohydantoin (6) with thiophene-2-carboxaldhyde and chloroacetic acid gives 5-(thiophen-2-ylidene)-3-[(p-tolylethylidene)amino] -2- thiohydantoin (8) and 3-[(p- tolylethylidene )amino] -2-thiohydantoin-5-yl acetic acid (10) . The mass spectral fragmentation patterns of some prepared thiazole and 2-thiohydantoin derivatives have been investigated in order to elucidate the structure of the synthesized compounds. The prepared compounds also exhibited antimicrobial activity.