4、BX3 和Me2S的络合物

       BX3 和Me2S的络合物为 BBr3 的改良方法。BBr3 或BCl3 和Me2S 的络合物是固体物，容易制备并在惰性气体中能长期保存。一般使用2 到4 倍量即可。

范例：

Table3. Cleavage of Ethers with BBr3.S(CH2)2 Complex

a) Reaction run at 83°C. b) GLC yield. C) Isoated yield.

     General Procedure for the Cleavage of Ethers with Boron Trihalide-Methyl sulfide Complex. To a flame-dried 100 mL flask under an atmosphere of nitrogen is added 1,2-dichloroethane (30 mL) and an amount of boron trihalide-methyl sulfide complex as indicated in Table 3. To this solution is added the desired number of equivalents of the aryl ether. The reaction mixture is stirred at reflux and monitored by either TLC or GLC where convenient. When the starting material disappears, the reaction mixture is hydrolyzed by adding water (30 mL), stirring for 20 min and diluting with ether. The organic phase is separated and washed with 1 M NaHCO and the phenol is subsequently taken up with 1 N NaOH (3×20 mL). The combined NaOH washings are acidified and the product is subsequently extracted into ether, dried (MgSO ) and the solvent is removed in vacuum.

5、BBr3/NaI/15-crown-5

这种体系为比BBr3 更强的去甲基化方法。也可用于脱除烷基甲基醚。

范例：

Table4. Dealkylation of Alkyl Methyl Ethers with BBr3-NaI-15-crown-5

a) Yield of isoated alcohol.

Typical Procedure. Cleavage of 3-Phenylpropanol Methyl Ether.

To a stirred solution of 3-phenylpropanol methyl ether (103 mg, 0.687 mmol) in dry methylene chloride (0.5 mL) is added 0.3 M solution of 15-crown-5 (13.7 mL, 6 equiv.) with NaI in methylene chloride followed by addition of 1 M solution of BBr3 (2.1 mL, 3 equiv.) in methylene chloride at -30°C under argon. The reaction mixture is stirred at the same temperature for 3 hrs, quenched by the addition of saturated aqueous NaHCO3 solution (2 mL) and worked up in the usual manner. Chromatographic purification of the crude product gives the pure alcohol (93 mg,100%), identical in all respects with an authentic sample.

6、Me2BBr

      文献报道，这个试剂去甲基化经由SN2 机理，因此，非常有效的只是断裂C-O 键，从而形成酚或醇，不易产生溴代副产物。

范例：

Table5. Cleavage of Ethers with (CH3)2BBr

a) Yield of isoated Product.

Typical Procedure. Cleavage of 1-Methoxydecane. To a cold (0°C), stirred solution of 1-methoxydodecane (1.03 mmol) and triethylamine (0.21 mmol, to neutralize traces of free acid) in dry methylene chloride (4.1 mL) under argon, is added a solution of dimethylboron bromide (1.34 M, 0.99 mL) in methylene chloride. The cooling bath is then removed and the resultant solution is then stirred at room temperature for 3 hrs. The reaction mixture is then cooled to 0°C, quenched with saturated aqueous sodium bicarbonate (2 mL) and diluted with ether (30 mL). The organic layer is separated, washed with saturated sodium bicarbonate (2 mL), water (2 mL) and brine (2 mL). The aqueous washings are extracted with ether and the organic layers are combined. After drying the resultant solution is concentrated and subjected to flash chromatography to provide pure 1-dodecanol (89%).