Reactivity of 3-(benzothiazol-2-yl)-3-oxopropanenitrile: A facile synthesis of novel polysubstituted thiophenes

The reaction of 3-(benzothiazol-2-yl)-3-oxopropanenitrile 1 with active methylene reagents 2a–d and sulfur afforded polysubstituted thiophenes 3a–c . The synthetic potential of the β-enaminonitrile moiety in 3a was explored. The reaction of 3a with active methylene reagents 2a–e afforded thieno[2,3-b]pyridine derivatives 6–8. Refluxing of 3a with acetic anhydride alone, with acetic anhydride/pyridine mixture, or with carbon disulfide in pyridine afforded the acetamido 9, thieno[2,3-d]pyrimidine 10, and pyrimidinedithiol 11 derivatives, respectively. The pyrimidinedithiol 11 was alkylated smoothly with methyl iodide to give the bis(methylthio) derivative 12. Also, compound 3a reacted with trichloroacetonitrile to give the thieno[2,3-d]pyrimidine derivative 14. Compound 3a reacted with triethyl orthoformate or formamide to give the ethoxymethylideneamino 15 and thieno[2,3-d]pyridine 16, respectively. Compound 15 reacted with hydrazine to afford thieno[2,3-d]pyridine 17, which reacted with various reagents such as chloroacetyl chloride, ethyl cyanoacetate, diethyl oxalate, or chloroethylformate to give 1,2,4-triazolo[1,5:1,6]pyrimidino-[4,5-b]thiophene derivatives 18a–c and 19, respectively. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:94–101, 2000