芳基亚胺酯还原甲基化
实际上，早在1974年，就已有文章报道了此类方法。该方法分为2步：
2010年，另一篇文章报道了对该方法的进一步改进，对多个反应因素更详细的研究结果，主要包括第一步缩合反应的催化剂和第二步亚胺酯还原所用的还原剂。
第一步反应的催化剂改为MCM-41-SO3H（关于该试剂的详细综述见：DOI：10.1080/00397911.2016.1212380）。
第二步反应的还原剂改为三乙酰基硼氢化钠，可以显著改善反应结果，包括收率和选择性：
底物拓展
实验操作
General procedure for the synthesis of mono-N-methyl anilines
A mixture of anilines (20 mmol), 0.10 g of MCM-41-SO3H, and 10 mL of triethyl orthoformate was heated at 120 C and the co-product ethanol was distilled off through a 10 cm Vigreux distillation column as it was produced. The progress of the reaction was monitored by GC or TLC. After the reaction was finished, the mixture was cooled to room temperature. Then the catalyst MCM-41-SO3H was filtered off, and washed with THF (5 mLx 3). The combined filtrate was concentrated in vacuo to recover the excess triethyl orthoformate.The resulting residual was dissolved in 15 mL of THF and directly performed the reduction at room temperature by dropwise addition in a period of ca. 1 h to a suspension of 40 mmol of NaBH3(OAc) (2 equiv), which was pre-prepared by addition of 2.40 g of CH3COOH (40 mmol) to a suspension of 1.51 g of NaBH4 (40 mmol) in 40 mL of THF. Then the mixture was stirred for another 2 h to complete the reduction. After the reduction completed, the reaction was carefully quenched by slowly adding 0.1 N NaOH (20 mL) until no gas emission. The resulting mixture was extracted with CH2Cl2 (50 mLx 3), the combined organic layers were dried over anhydrous Na2SO4, filtered off, and the solvent was removed under reduced pressure. The residual was purifified by flflash column chromatography on basic Al2O3 (petroleum ether/ethyl acetate) to afford the desired mono-N-methyl anilines.参考文献：
Synthesis 1974, 55-56. DOI: 10.1055/s-1974-23242Tetrahedron 66 (2010) 7142-7148, DOI: 10.1016/j.tet.2010.06.091
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