这是最为经典和简单的甲基芳基醚水解去甲基的方法。一般使用过量的浓HI酸回流下、或者大大过量的48% HBr或37% HCl在HOAc或Ac2O中回流，反应完后，浓缩去除过量的酸，加入水，用有机溶剂萃取，然后进一步纯化即可。特点是操作和后处理简单、方便。但要求底物对强酸稳定，对于有些底物，易形成卤代苯副产物。
在48%HBr中加入相转移催化剂是对仅使用强质子酸如48%HBr的改进。加入相转移催化剂后，能提高去甲基化的效率，大大缩短反应的时间。此反应是在一个多相体系（水和有机）中进行，可使用的相转移催化剂有四丁基溴化铵，十六碳烷基三丁基溴化磷,四辛基溴化铵，三辛基甲基溴化铵等。对于甲基芳基醚，一般使用5 mol量的HBr，对于甲基烃基醚，一般使用10 mol量的HBr；值得注意的是，反应的收率和时间不是依赖于使用那一种相转移催化剂，而是依赖于相转移催化剂的浓度和其在有机相的溶解度。
反应实例
Typical Pocedure
The ether (300 mg) was dissolved in 48% HBr (50 mL) and heated for 1 hrunder reflux. The reaction mixture was evaporated to dryness and extracted withether. The ethereal extract was washed with sodium carbonate solution andwater, dried and evaporated. The residue was recrystallized from chloroform togive the product (120 mg, 40%).
【 I. Kawasaki, K. Matsuda, and T. Kaneko, Bull. Chem. Soc. Jpn., 1971, 44, 1986.】
Typical Pocedure
Cleavage of Di-n-octyl Ether. Di-n-octyl ether (12.1 g, 0.05 mol), 47% aqueous hydrobromic acid (56mL,0.5 mol), and hexadecyltributylphosphonium bromide (2.5 g, 0.005 mol) are mixed in a flask equipped with amagnetic stirrer and reflux condenser, and heated at 115°C (inner temperature) with stirring for 5 hrs.After this time GLC analysis (SE 30, 3% over chromosorb sulfate, and distilledto give pure 1-bromooctane. The organic layer is separated, dried with sodiumsulfate, and distilled to give pure 1-bromooctane; yield: 17.5 g (91%), bp 88°/torr. By treating thedistillation residue with hexane, 2.3 g(92%) of pure phosphonium bromide are recovered, mp 54-56°C. In the case of aryl alkyl ethers, aqueousalkaline extraction of the organic phase affords the corresponding phenol.
【 D. Landini, F. Montanari and F. Rolla, Synthesis, 1978,771.】
本文非原创内容，版权归原作者所有。
