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methyl 2-(phenylethynyl)benzoxazole-5-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
73%
With Pd(II)(N-(3-(1-hydroxy-3-phenylpropan-2-yl carbamoyl)benzylidene)-2-methylpropan-2-amineoxide(-2H)); silver(l) oxide; In N,N-dimethyl-formamide; at 80℃;
General procedure: To an oven dried 25 mL round bottom flask, palladium complex (7 mg, 3 mol %), silver(I) oxide (229 mg, 1 mmol) and aryl propiolic acid (1 mmol), under air, were added. Azole substrate (0.5 mmol) in DMF (4 mL) was added to the reaction mixture. The reaction mixture was stirred at 80 C for 6-8 h. The reaction mixture was diluted with EtOAc then filtered through filter paper. The filtrate was quenched with Ice cold water and then, aqueous layer was extracted with EtOAc. The organic phase was washed with NaCl (satd aq), dried with Na2SO4, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography.
methyl 2-(phenylethynyl)benzoxazole-5-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
74%
With Pd(II)(N-(3-(1-hydroxy-3-phenylpropan-2-yl carbamoyl)benzylidene)-2-methylpropan-2-amineoxide(-2H)); caesium carbonate; silver(l) oxide; In N,N-dimethyl-formamide; at 85℃; for 8h;
General procedure: To an oven dried 25 mL round bottom flask, palladium complex (7 mg, 3 mol %), cesium carbonate (325 mg, 1 mmol), silver(I) oxide (229 mg, 1 mmol) and azole substrate (0.5 mmol) in 2 mL DMF, under air, were added. Phenyl acetylene substrate (1 mmol) in DMF (2 mL) was added to the reaction vessel slowly by dropping funnel over 2 h while stirring the reaction mixture on preheated oil bath at 85 C. The reaction was allowed to stir for 6 h at the same temperature. The reaction mixture was diluted with EtOAc then filtered through filter paper. The filtrate was quenched with Ice coldwater and then, aqueous layer was extracted with EtOAc. The organic phase was washed with NaCl (satd aq), dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography.
methyl 2-(2-benzamidophenyl)-1,3-benzoxazole-5-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
89%
With copper(l) iodide; palladium diacetate; caesium carbonate; 4,5-bis(diphenylphos4,5-bis(diphenylphosphino)-9,9-dimethylxanthenephino)-9,9-dimethylxanthene; In toluene; for 20h;Inert atmosphere; Reflux;
General procedure: To a degassed solution (N2 was purged for 10 min) of methyl 1,3-benzoxazole-4-carboxylate (150 mg, 0.847mmol) and N-(2-iodophenyl)benzamide 2a (273 mg, 0.847 mmol) in anhydrous toluene (4ml) , CuI (32 mg, 0.169 mmol), xantphos (98 mg, 0.169 mmol), Pd(OAc)2 (10 mg, 0.042 mmol), Cs2CO3 (685 mg, 2.117 mmol) were added at room temperature under nitrogen atmosphere. Reaction mixture was continued for 20 hours at reflux condition. After the completetion of the reaction (monitored by TLC), Reaction mixture was filtered through celite bed and washed with methanol (10 ml),filtrate was concentrated. Crude mass which was purified by column chromatography over silica gel (230-400 mesh) using DCM-Methanol (1:9) as elutant to affordthe products 3a (284 mg) as white solid. All the other compounds 3b-3r were prepared similarly following the above procedure.
methyl 2-(4-hydroxyphenyl)benzo[d]oxazole-5-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
67%
With palladium diacetate; copper(II) acetate monohydrate; potassium carbonate; tricyclohexylphosphine; In toluene; at 160℃; for 0.5h;Microwave irradiation;
At 20 from Preparative Example 1The obtained methylbenzo [d] oxazole-5-carboxylate 354.1 mg (2.0 mmol) was dissolved in toluene (20 mL, 0.1 M)4-Bromophenol (380.6 mg, 2.2 mmol), Palladium acetate (Pd (OAc) 2, 4.5 mg, 1 mol%),Copper acetate monohydrate (Cu (OAc) 2 .H2O, 72.6 mg, 20 mol%),Tricyclohexylphosphine (PCy3, 280.4 mg, 50 mol%) And potassium carbonate (K2CO3, 552.8 mg, 4 mmol) were slowly added.The reaction mixture was reacted in a microwave at 160 C for 0.5 hour under a condition of 200W, The reaction was terminated by the addition of aqueous ammonium chloride solution, Ethyl acetate (10 mL) was extracted and extracted three times. After the water of the organic layer was removed with sodium sulfate,The solvent was concentrated with a vacuum distillation apparatus.The residue was purified by silica gel chromatography to give the title compoundMethyl 2- (4-hydroxyphenyl) benzo [d] oxazole-5-carboxylate(360.6 mg, 67%) was obtained
3-amino-4-hydroxybenzoic acid 5.0 g (32.7 mmol)Was dissolved in methanol (327 mL, 0.1 M) Of concentrated hydrochloric acid at 0 (16.3 mL, 2.0 M)Was slowly added.After the reaction mixture was reacted at 80 DEG C for 12 hours,300 mL of distilled water was added to dilute the solution, and 1.0 N NaOH aqueous solution was gradually added at 0 C to terminate the reaction.Separation three times with chloroform / methanol (10: 1, 100 mL)And the water of the organic layer was removed with sodium sulfate,The solvent was concentrated with a vacuum distillation apparatus. The residue is then transferred to a microwave tube,Was dissolved in trimethyl orthoformate (32.7 mL, 1.0 M) and reacted with microwave at 150 C for 1 hour under 200W condition.After the reaction, the solvent was concentrated using a vacuum distillation apparatus,The residue was purified by silica gel chromatography to give the title compoundMethylbenzo [d]Oxazole-5-carboxylateThe agent was obtained.
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