5-羟基-4-甲氧基-2-取代基苯甲醛合成研究

Synthesis of 5-Hodroxy-4-Methoxy-2-Substitutedbenzaldehyde

以藜芦醛为起始原料,制取2-溴-5-羟基-4-甲氧基苯甲醛(Ⅰ)和5-羟基-4-甲氧基-2-硝基苯甲醛(Ⅱ)。藜芦醛经过溴化和硝化分别得到中间体2-溴-4,5-二甲氧基苯甲醛和4,5-二甲氧基-2-硝基苯甲醛。蛋氨酸存在下,中间体经浓硫酸水解,分别合成了Ⅰ和Ⅱ。产品结构经过核磁共振谱、红外光谱、质谱验证。产物Ⅰ和Ⅱ的收率分别为85.0%和收率为65.0%。实验结果得出藜芦醛硝化和溴化反应的定位规律,并推测水解过程中蛋氨酸分别与Ⅰ和Ⅱ形成多氢键缔合物的作用机制,并对蛋氨酸与Ⅱ的形成的多氢键缔合物分子在HF/6-31G*水平上单点能进行计算,其总能量为-1532.5hartree。

2-Bromo-5-hydroxy-4-methoxybenzaldehyde （Ⅰ） and 5-hydroxy-4-methoxy-2-nitrobenzaldehyde （Ⅱ） were synthesized. The intermediates 2-bromo-4,5-dimethoxybenzaldehyde and 4,5-dimethoxy-2-nitrobenzaldehyde were synthesized firstly from veratraldehyde through bromination and nitration respectively. In the presence of molar quantity methionine, the 5th-position methoxys of the intermediates were in turn hydrolysed to hydoxy by concentrated sulfuric acid to give Ⅰ and Ⅱ. The chemical structures of the titled compounds were confirmed by 1↑H-NMR, IR and MS spectrum： The yields of compounds Ⅰ and Ⅱ are 85.0% and 65.0% respectively. The orientations of the bromination and nitration steps were suggested and discussed. The mechanism of methionine in the hydrolysis step may involve in the formation of the multiple hydrogen bonded association complex, and the calculated single point energy （E=- 1532.5 hartree） of the multiple hydrogen bonded association complex seems to show it is possibly existed at the RHF/6-31G level.