| Nitrile is a kind of important chemical raw material and organic intermediates,which is constituted major building blocks of the pharmaceutical,fine chemical,dye,functional materials and agrochemical.In the traditional synthesis process,the hazardous reagent and expensive catalyst are generally required.Consequently,the development of novel and efficient methods for the synthesis of aryl nitriles have attracted much interest of organic chemists.In this paper,we successfully developed a one-pot,sequent of electrochemical procedure for the synthesis of aryl nitriles via selective electro-oxidation of C-H bond for constituting the intermediate of aldehyde,with hydroxylamine as N source.Three electrochemical cyanidation systems of aromatic aldehydes,aromatic primary alcohols and methyl arenes were investigated and optimized respectively.The scope of the substrate was investigated under the optimized conditions.The plausible reaction mechanism for the synthesis of aryl nitriles via selective electro-oxidation of C-H bond was discussed.The main contents and results are as followings:?.The investigation of the electrochemical cyanidation system of p-MeOBA by CCE showed that chemically reacted for two hours at 60?using 0.05 mol·L-1p-MeOBA as substrate,0.15 mol·L-11 hydroxylamine hydrochloride as N source,0.05mol·L-1Bu4NClO4 as electrolyte in DMF solution with 30%of H2O,and then electrolyzed for 5 hours at galvanostatic of 10 mA·cm-22 equipped with platinum as the anode,lead as the cathode,the yield of p-methoxybenzonitrile?p-MeOBN?was up to89%,and the current efficiency was up to 72%.Lead was excellent cathode material in the procedure.The conversion of the substrate was increased under the addition of H2O.The substrate was easy to be oxidized to produce by-product acid in CH3CN solution.The degree of further oxidation of aldehydes was reduced by step electrolysis.In the investigation of the scope of substrates,the aromatic aldehydes with electron-donating group?-OMe,-Me,-t-Bu?was lower than that with the electron-withdrawing group?-F,-Cl,-Br?on the yield of nitriles,while it was easy to be deeply oxidized to produce the corresponding acid.?.The investigation of the electrooxidation activity of p-MeOBnOH by CV showed that the best was in the system of CH3CN with 30%of H2O and 0.35 mol·L-1H2SO4.The investigation of electrooxidation cyanidation system of p-MeOBnOH by CCE showed that using 0.05 mol·L-11 p-MeOBnOH as substrate,0.15 mol·L-1hydroxylamine as N source,0.05 mol·L-1Bu4NClO4 as electrolyte,platinum as the anode and lead as the cathode,in DMSO solution with 0.15 mol·L-11 H2SO4 and 30%of H2O,electrolyzed for 8 h at galvanostatic of 12.5 mA·cm-2,60?,the yield of p-MeOBN was up to 90%,and current efficiency was up to 68%.In the investigation of the scope of substrates,which was mainly influenced by the solvent and oxidation current,and it was more suitable for the electrooxidation cyanidation in CH3CN system by adjusting the current density.The yield of the corresponding nitriles was obtained?1595%?from various alcohols with electron-absorbing groups?-F,-Cl,-Br?or electron-donor groups?-OMe,-Me,-t-Bu?.?.The investigation of the electrooxidation activity of p-MeOBT by CV showed that the best was in the system of CH3CN with 30%of H2O and 0.15 mol·L-1H2SO4.The investigation of electrooxidation cyanidation system of p-MeOBT by CCE showed that using 0.1 mol·L-1p-MeOBT as substrate,0.3 mol·L-1hydroxylamine as N source,0.05 mol·L-11 Bu4NClO4 as the electrolyte,in the system of CH3CN with 30%of H2O and 0.15 mol·L-1H2SO4 at galvanostatic of 12.5 mA·cm-2equipped with platinum as the anode and lead as the cathode,60?,electrolyzed for13 h,the yield of p-MeOBN was up to 81%,and the current efficiency was up to 80%.In the investigation of the scope of substrate,the procedure was provided a moderate to good yields?2981%?of aryl nitriles.The substrate with electron-donor group was easy to produce acid,while the substrate with electron-absorbing group was easy to pause in the steps of the intermediate of alcohols and aldehydes during the cyanidation process.A plausible mechanism for the electro-oxidation cyanidation procedure was discussed. |
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