Table7. Dealkylation of Alkyl Aryl Ether with sodium N-Methylanilide in presence of HMPT
a) Yield of isoated Product.
Typical Procedure. Cleavage of 1,2,4-Trimethoxybenzene.
N-Methylaniline (2.68 g, 25mmol) is added dropwise at 65°C to a stirred suspension of sodium hydride (0.6 g, 25 mmol) in sodium-dried xylene (5 mL) and HMPT (4.26 g, 25 mmol, distilled over calcium hydride and stored in dark over molecular sieves, 8A°). After 15 min, the ether (12.5 mmol in the minimum amount of xylene) is added and the mixture is heated at 85°C. The reaction is monitored by GLC (3 m SE 30 column) and by TLC. When the starting material disappears (6 hrs) the mixture is poured into water, acidified with dilute hydrochloric acid, and the product is extracted with ether. The ether phase is washed with dilute hydrochloric acid (2×90 mL) to remove HMPT and the amines and then the product is extracted with 10% sodium hydroxide solution (2×90 mL). The aqueous phase is acidified with dilute hydrochloric acid and extracted with ether (3×90 mL). The organic phase is dried over calcium chloride and concentrated on a rotary evaporator to give pure 2,5-dimethoxyphenol; yield: 1.9 g (90%). The product may be further purified by column chromatography on silica gel.
在 EtSNa/DMF 体系中，双键和溴代物不受影响；有时具有选择性去甲基化，如下表。
Table 8. Dealkylation of Ethers by Sodium Ethanethiolate
Typical Procedure. Dealkylation of m-Methoxytoluene. Ethanethiol (1.25 g, 11.8 mmol) dissolved in dry DMF (20 mL) is added to a suspension of sodium hydride (1.0 g of a 50% oil dispersion) in dry DMF (10 mL) under an atmosphere of nitrogen. The mixture is stirred for 5min before solution of m-methoxytoluene (1.09 g) in dry DMF is added. The solution is then refluxed for 3 hrs. The cooled mixture is acidified with 10% aqueous hydrochloric acid and extracted with ether. The ether layer is washed with water and extracted with 5% sodium hydroxide. The alkaline extracts are then acidified and reextracted with ether. The ethereal solution is washed with water, dried and evaporated to give m-cresol as a light brown oil; yield: 0.85 g (78%).