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With potassium hydroxide In ethanol Heating; |
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With potassium hydroxide In ethanol for 8h; Heating; |
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With potassium hydroxide In ethanol |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With potassium hydroxide In ethanol Reflux;
Stage #2: With hydrogenchloride In ethanol; water |
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With potassium hydroxide In ethanol Reflux; |
General Procedure for the Synthesis of 5-Substituted Aryl/aralkyl-1,3,4-oxadiazol-2-thiols (4a-k)
General procedure: The aryl/aralkyl acid hydrazides (0.01 mol, 3a-k) were dissolved in ethanol(35-40 mL) followed by the addition of KOH (0.03 mol) and CS2 (0.01 mol) in 250 mLround bottom flask fitted with a reflux condenser. The reaction mixture was refluxedfor 3-6 h along with proper stirring and the progress of reaction was monitored byTLC. After completion of reaction, the reaction mixture was diluted with distilled H2O(70-75 mL) and acidified with dilute HCl (pH 2-3) to convert salt of oxadiazole into acidicform. Precipitates of corresponding 5-substituted-1,3,4-oxadiazole-2-thiols (4a-k) werefiltered, washed with distilled water, and dried. To get the pure product, precipitates wererecrystallized from methanol.17-19 |
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With potassium hydroxide In ethanol; water Reflux; |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With potassium hydroxide In ethanol
Stage #2: With hydrogenchloride In water |
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With potassium hydroxide In ethanol for 20h; Reflux; |
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With potassium hydroxide In ethanol Reflux; |
2.4. Procedure for the synthesis of 5-substituted-1,3,4-oxadiazol-2-thiols (4a-o)
General procedure: The aralkyl/aryl acid hydrazides (0.01 mol; 3a-o) were dissolved in 20 mLabsolute C2H5OH in a 250 mL of round bottom flask. Solid KOH (0.02 mol)and carbon disulphide (0.02 mol) were added to reaction flask. The reactioncontents were refluxed for 4-5 hrs with continuous stirring. H2S was evolvedduring the completion of reaction. Completion of reaction was confirmed bythin layer chromatography by using n-hexane and ethyl acetate (3:2) as mobilephase to develop a chromatogram. After confirmation, cold distilled water wasadded to the flask contents along with the addition of dilute HCl (pH 4-5).Precipitates of title compounds were filtered, washed with distilled waterand dried. To obtain the pure products, precipitates were recrystallized frommethanol. |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With potassium hydroxide In ethanol Reflux;
Stage #2: With hydrogenchloride |
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With hydrazine hydrate; potassium hydroxide In ethanol Reflux; |
General procedure for synthesis of 5-((un)substituted-phenyl)-1,3,4-oxadiazol-2-thiols (VIIa-n).
General procedure: Solid KOH (0.03 mol) was dissolved in 25 mL EtOH on reflux in a 100 mL round-bottom flask. (Un)Substituted-benzohydrazide (VIa-n) (0.03 mol) was refluxed with CS2 (0.06 mol) in this basified EtOH for 5-6 h. The reaction was monitored by TLC. At completion, excess ice-cold distilled water (60 mL) wasadded to form homogeneous solution. pH was adjusted to 5-6 by pouring dilute HCl; precipitatethus formed was filtered, washed with distilled water and dried. The formed products (VIIa-n) were also re-crystallized from EtOH [18, 19]. |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With potassium hydroxide In ethanol at 80℃;
Stage #2: With hydrogenchloride; water at 20℃; |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With potassium hydroxide In ethanol
Stage #2: With hydrogenchloride In water |
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With potassium hydroxide In ethanol; water at 95℃; for 16h; Inert atmosphere; |
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Stage #1: carbon disulfide; 3-chlorobenzhydrazide With sodium hydroxide
Stage #2: With hydrogenchloride |
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With potassium hydroxide In ethanol for 6h; Reflux; |
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In N,N-dimethyl-formamide for 10h; Sonication; |
4.2.1. general procedure for the synthesis of 2-mercapto-1,3,4-oxadiazolederivatives (compounds 85-110)
General procedure: Carbon disulfide (50 mmol 4.7 mL) was added dropwise to the suspension including carboxyhydrazides (compound 59-84, 50 mmol) in DMF (5 mL) processed to an ultrasonic bath for 10 h. Hydrogen sulfide emission was treated with a saturated solution of sodium bicarbonate.The reaction mixture was added to 20 g crushed ice containing excess of salt. The solid phase was filtered with Buchner funnel, washed with water, and dried to obtain compound 85-110, respectively. |
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With potassium hydroxide In ethanol for 7h; Reflux; |
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With potassium hydroxide In ethanol for 12h; Reflux; |
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