| 93% |
With morpholine; In acetic acid; at 80℃; for 4h; |
Typical procedure for the condensation synthesis of compound 3a: Benzoin 1a (1.0 equiv.), 1,2-diamine 2a (2.0 equiv.), oxidant (0.35 mol%), and Yb/NaY catalyst (Yb3+ 0.05 equiv.) were reacted in solvent (5 mL) in a 25 mL round bottom flask. The mixture was stirred for 4 h at 80 C. After completion of the reaction, the mixture was centrifuged and washed with ethyl acetate (3 times 10 mL). The solid catalyst was recovered and dried at 80 C for 2 h. The combined organic solution was evaporated under reduced pressure and purified by column chromatography on silica gel, eluting with petroleum ether/ethyl acetate (20:1, v/v), to get 2,3-diphenyl-quinoxaline 3a. Other products were synthesized through typical procedures. All 1H NMR results are summarized in Supporting information. The configuration of compounds 3a-3n was assigned by comparing 1H NMR data with known compounds [19-23]. |
| 91% |
With 2,2,6,6-Tetramethyl-1-piperidinyloxy free radical; copper(II) acetate monohydrate; In N,N-dimethyl-formamide; at 110℃; for 0.5h;Microwave irradiation; |
General procedure: 2-hydroxyacetophenone (0.068g, 0.50mmol), o-phenylenediamine (0.054g, 0.50 mmol), copper acetate monohydrate (10mg, 0.050mmol) and TEMPO (7.8mg, 0.050 mmol) were dissolved in DMF (2 ml) in a microwave tube equipped with a stirrer bar. The mixture was irradiated for 30 minutes at 110 C under open vessel conditions. Water was added to the mixture and the resulting solution was then extracted with dichloromethane and concentrated to produce the crude product, which was subsequently purified using radial chromatography to produce the title compound as an orange solid (0.097g, 94%) mp = 80 - 81C. |
| 88% |
With potassium fluoride on basic alumina; at 80℃; for 5h; |
General procedure: A mixture of 1,2-diamine (1.2 mmol) and α-hydroxy ketone compound (1 mmol) was intimately mixed with pre-activated KF-alumina (0.5 g) (Basic; Grade: Brockmann 1, and activated by heating under vacuum at 150 C until bubbling ceases and then cooled to room temperature under vacuum) and the solid mixture was stirred with a magnetic spin bar at 80 C for hours as indicated in refPreviewPlaceHolderTable 2. After the reaction was complete, the solid mixture washed with diethyl ether (3 × 10 mL) and the solid was filtered off. The filtrate was concentrated and passed through a short column of silica gel to afford the quinoxalines. The desired product was pure on TLC and characterized by spectral (IR, 1H and 13C NMR) data and compared to those reported. |
| 77% |
With silica gel; at 150℃; for 0.25h;Microwave irradiation; |
General procedure: 2-Hydroxyacetophenone (0.068 g, 0.50 mmol), o-phenylenediamine (0.054 g, 0.50 mmol) and silica gel (5 mg) were added to a microwave vessel and irradiated under open or closed vessel conditions for 10 minutes at 70oC after which the reaction vessel was rapidly cooled to 50oC by the microwave instrument. The reaction mixture was diluted with EtOAc and passed through a short silica plug. The solvent was removed in vacuo to produce a crude product that was purified using radial chromatography to produce the title compound as an orange solid (0.039 g, 38 %, open vessel); |
| 72% |
With cesium hydroxide; In dimethyl sulfoxide; at 30℃; for 24h; |
Reaction tubes are sequentially added CsOH (0.0126g, 15mol %), O-phenylenediamine (0.75mmol, 1 . 5equiv.) and bisphenylmethyl second grade alcohol ketone (0.106g, 0 . 5mmol,), then adding DMSO (1.0 ml) as the solvent, plus atmospheric air ball, under room temperature (30oC) reaction 24h.TLC monitoring after the reaction is complete, post chromatographic separation and purification of product, separation yield 72% |
| 70% |
With gallium(III) perchlorate; In ethanol;Reflux; |
General procedure: Representative experimental procedure for the synthesis of 2-phenylquinoxaline (3a) (Table 2, entry 1): A mixture of o-phenylenediamine (1a, 0.0541 g, 0.5 mmol), 2-hydroxyaceto-phenone (2a, 0.0681 g, 0.5 mmol) and Ga(ClO4)3 (0.018g, 0.05 mmol) in EtOH (3 mL) was stirred at room temperature. The progress of the reaction was monitored by TLC. After completion of the reaction, the mixture was directly purified by silica gel column chromatography (petroleum ether/ethyl acetate, 10:1) to afford the product 3a. The structures of all products were confirmed by IR, 1H NMR spectroscopy and melting points, which were consistent with literature data. |
|
With graphene oxide; In neat (no solvent); at 80℃; for 1.5h;Sealed tube; Green chemistry; |
General procedure: A mixture of 2-nitro aniline (1 mmol), hydrazine monohydrate (2.2 mmol) and GO (20 mg) was taken in a screw-capped glass tube and stirred the reaction mixture for 3-4 h at 100 C temperature. After the complete reduction (as monitored by tlc and by the colour change of the reaction mixture from yellow to total black), 1,2-dicarbonyl compound (or α-hydroxy ketone) (1 mmol) was added to the reaction mixture and stirred for few hours at 60 C (80 C for α-hydroxy ketone), as mentioned in the Table 2. After completion of the reaction (checked by tlc), the reaction mixture was cooled to room temperature. Water and ethyl acetate were added to the reaction mixture and centrifuge (5000 rpm) the whole reaction mixture to separate the GO (which is now converted to rGO). This process was repeated for three times. The combined organic-aqueous part was then taken in a separating funnel and the organic layer was separated from aqueous layer, and finally dried over anhydrous Na2SO4. Evaporation of the solvent afforded the desired quinoxaline (satisfactorily pure), which was further purified by passing through a short column of silica gel and using the light petroleum ether:ethyl acetate (97:3) as the eluent. All products were characterized by 1H, 13C NMR data and compared with the reported melting points for known solid compounds. |
|
With acetic acid; MORPHIN; at 80℃; for 4h; |
A solution of 1 mmol of benzoin, 2 mmol of o-phenylenediamine, 0.35 mmol of morphine and a Yb / NaY molecular sieve catalyst containing 0. 05 mmol of Yb3 + was placed in a 25 mL round bottom flask. 5 mL of acetic acid and magnet were added and stirred at 80 C for 4 h. The resulting mixture was filtered and the residue was a Yb / NaY molecular sieve catalyst, recovered, and the filtrate was separated by column chromatography to give pure product, |
|
With biomass-derived carbon; In toluene; at 100℃; for 4h; |
General procedure: Briefly, a mixture of o-phenylendiamine 2 (1 mmol) and benzoin 3(1 mmol), in toluene (5 mL), in a three-necked vessel, equipped withthermometer, was placed on a multiexperiment work station StarFish(Radleys Discovery Technologies IUK). When the temperature reaches100 C, the catalyst was added (25 mg) and the reaction mixture wasstirred during 240 min. The samples were periodically taken at 15, 30,60, 120, 180 and 240 min and the catalyst filtered off and the solventevaporated in vacuo. The catalysts were milled and sieved to dp<0.25 mm, in order to avoid mass transfer limitations. Before use, carboncatalysts were activated at 60 C overnight. |
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