Synthesis of oxadiazoles, thiadiazoles and triazoles derived from benzo[b]thiophene.
In this work 3-chloro-2-chlorocarbonylbenzo[b]thiophene (1) was prepared from cinnamic acid and then converted into the acid hydrazide 2. The azomethines 3a-e were prepared from the corresponding aryl aldehydes and the acid hydrazide 2. Treatment of compound 2 with formic acid gave the N-formyl acid hydrazide 4, which upon refluxing with phosphorous pentoxide or phosphorous pentasulphide in xylene yielded the corresponding 2- (3-chloro-1-benzothien-2-yl)-1,3,4-oxadiazole (5) and 2-(3-chloro-1-benzo-thien-2-yl)-1,3,4- thiadiazole (6). Reaction of 1-thiosemicarbazide 7 with NaOH leads to ring closure giving 5- (3-chloro-1-benzothien-2- yl)-4H-triazole-3-thiol (8) which is converted into a number of derivatives 9-12 Reaction of 2 with phenyl isothiocyanate and NaOH afforded 5-(3-chloro- 1-benzothien-2-yl)-4-(phenyl)-4H-1,2,4-triazole-3-thiol (14).
Sharba
A Hussain K
AH
Department of Chemistry, College of Science, Al-Mustansirya University, Baghdad, Iraq. hussainirk@yahoo.com
Al-Bayati
R H
RH
Aouad
M
M
Rezki
N
N
D010069:Oxadiazoles / Q000138:chemical synthesis* / Q000737:chemistry; D013830:Thiadiazoles / Q000138:chemical synthesis* / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry*; D014230:Triazoles / Q000138:chemical synthesis* / Q000737:chemistry
D010069:Oxadiazoles; D013830:Thiadiazoles; D013876:Thiophenes; D014230:Triazoles; C088015:benzothiophene