AlCl3/CH3CN和AlBr3/CH3CN是【Bull. Chem. Soc. Jpn., 1995, 68, 2033】一類常用的去甲基化方法，其操作類似BBr3的使用，只是一般反應(yīng)溫度在0℃到室溫。另外加入硫化物，由于硫的親核性更強(qiáng)，可以增加反應(yīng)活性。AlBr3/EtSH,AlCl3/EtSH, AlCl3/HSCH2CH2SH體系的活性很高，分子中酯、醛、酮、雙鍵不穩(wěn)定，但酯在AlCl3/EtSH/CH2Cl2體系相對(duì)穩(wěn)定。
反應(yīng)機(jī)理
加入硫代物
反應(yīng)實(shí)例
Typical Procedure. To dichloromethane (1 mL) or CH3CN (1 mL) wasadded aluminum chloride (3.0 mmol) at 0 ℃. Theresulting solution was warmed to room temperature, and the ether (1.0 mmol) wasadded with stirring. After being stirred for 3-12 h, the reaction mixture was pouredinto water, acidified with dilute HC1, and extracted with dichloromethane. Theorganic layer was treated as usual to give a crude product. Chromatography over a silica gelcolumn gave the desired product.
【Y. Kawamura, H.Takatsuki, F. Torii, and T. Horie, Bull. Chem. Soc. Jpn., 1994,67, 511.】
General Procedure for Demethylation. To a stirredsolution of aluminum halide in ethanethiol cooled in an ice-water bath wasadded the substrate.The reaction was monitored by TLC (aluminum halide was quenched bymethanol in the capillary). The reaction mixture was poured into water,acidified with dilute HC1, and extracted with dichloromethane. The organiclayer was shaken with brine, dried (Na2SO4), filtered,and then evaporated to leave a crude material, which was purified bychromatography over a silica gel column.
AlCl3/EtSH/CH2Cl2體系：To a mixture of dry ethanethiol (1 mL) and dichloromethane (1 mL) was added aluminum chloride (0.40 g, 3.0 mmol) at 0 oC. The resulting solution was warmed to room temperature,and the ether (0.194 g,1.0 mmol) was added with stirring. After being stirred for 9.5 h, the reactionmixture was poured into water, acidified with dilute HCl, and extracted with dichloromethane.The organic layer was treated as usual to give a crude product.Chromatography over a silica gel column gave the desired product (0.157 g, 95.5%) identical with anauthentic sample.
AlCl3/EtSH 體系：To a solutionof aluminum chloride (47 mg, 0.35 mmol) in dry ethanethiol (1 mL) was added the ether (11 mg, 0.03mmol) at 0 oC. After being stirred for 2.5 h at 0 oC, the reactionmixture was poured into water and extracted with dichloromethane. The usual workup of theorganic layer gave the product: 7.5 mg (81.5%).
【 M. node, K.Nishide, K. Fuji and E. Fujita, J. Org. Chem. 1980, 45,4275. 】
