摘要
2，2，6，6-四甲基-N-氧自由基哌啶醇（2，2，6，6-tetramethyl-piperidin-4-ol-N-oxyl，TEMPO）与氯乙酰氯反应生成2-氯乙酸-2，2，6，6-四甲基-1-氧-4-哌啶醇酯，该酯与N-甲基咪唑发生季铵化反应后再与六氟磷酸钾进行离子交换制得2，2，6，6-四甲基-N-氧自由基哌啶醇负载离子液体TEMPO-IL。温和条件下以离子液体1-甲基-3-丁基咪唑六氟磷酸盐（1-butyl-3-methylimidazolium hexafluorophosphate，[bmim]PF6）为溶剂，TEMPO-IL和CuCl为催化剂，分子氧氧化各种醇为相应的醛或酮。研究发现，该氧化体系对苄醇和烯丙醇有较好的氧化效果，65℃下反应10h左右，转化率可达99％，收率可达80％～90％。氧化体系对醛酮有高度的选择性，在实验所采用的条件范围内未检测到有羧酸生成。溶剂和催化剂可循环使用，在苯甲醇的氧化中，溶剂和催化剂循环使用6次，反应转化率和苯甲醛的收率保持不变。
Reaction of 2,2,6,6-tetramethylpiperidin-4-ol-N-oxyl （TEMPO） with 2-chloroacetyl chloride gave 4-chloroacetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl. An ionic-liquid immobilized TEMPO （TEMPO-IL） was then obtained via the quaternization of 1-methyl-1H-imidazole with 4-chloroacetoxy-2,2,6,6-tetramethyl-piper- idine-N-oxyl followed by ion exchange with KPF6. A selective and mild ionic-liquid immobilized TEMPO/CuCl catalyzed oxidation procedure of alcohols to the corresponding aldehydes and ketones with molecular oxygen in ionic liquid [ bmim] PF6 was developed. Oxidation reactions of benzylic and allylic alcohols were completed in about 10 hours at 65 ℃ with a conversion of 99% and 80% - 90% product yields. Oxidation reactions of aliphatic and heterocyclic alcohols were more difficult with low conversion and yield. The reaction was highly product-selective and in any case only aldehyde or ketone was formed. No carboxylic acid was detected. The solvent and catalyst were easily recovered and reused in the reaction. In the case of the oxidation of benzyl alcohol, the solvent and catalyst were recovered and reused for 6 times with no decreases of benzyl alcohol conversion and product yield.
出处
《应用化学》
CAS
CSCD
北大核心
2007年第11期1327-1331,共5页
Chinese Journal of Applied Chemistry
关键词
功能离子液体
分子氧
氧化
醇
task-specific ionic liquids, molecular oxygen, oxidation, alcohol
