Chemotherapeutical Agents, V. Syntheses and Activities of Novel Pyrimidines Derived from 5‐Cyano‐6‐aryl‐2‐thiouracil

The 5‐cyano‐6‐aryl‐2‐thiouracils 1a–d were prepared1,2) for the syntheses of several other pyrimidine derivatives. In basic medium 1a reacted with picryl chloride yielding the unexpected benzothiazolo‐pyrimidine 2. Heating a mixture of 1 and 1,2‐dibromoethane in DMF in basic medium gave the thiazolopyrimidines 3a, d, while the reaction of 1 with 1,3‐dibromopropane and 1,3‐dibromo‐2‐propanol under similar conditions yielded the pyrimido‐thiazine 3b, c, e. Alkylation of 1 with alkyl halides in alkaline medium in 1:2 and 1:1 ratios gave the di‐ and monoalkyl derivatives 4 and 5, respectively. With hydrazine hydrate, 4a yielded the 2‐hydrazinopyrimidine 6 which cyclized to give the triazolo‐pyrimidine 7 on refluxing in formic acid. Similar reaction conditions were maintained for attempts to cyclize 6 with acetic and propionic acid, but always the acylhydrazino derivatives 8a, b were isolated. Reaction of 6 with methyl 2‐cyano‐3,3‐bis(methylthio)acrylate or with acetylacetone yielded the pyrazolo‐pyrimidines 9 and 10, respectively. All products were screened for their potential fungicidal, bactericidal, and antiviral activities since several related compounds were shown to possess antimicrobial activities in a primary screening.