Synthesis of[uniformly ring-14C]-labelled 4-hydroxybenzaldehyde, vanillin, and protocatechualdehyde
作者:Rong Ji、Andreas Schäffer
DOI:10.1002/jlcr.815
日期:2004.3.30
[Uniformly ring-14C]-labelled 4-hydroxybenzaldehyde, vanillin, and protocatechualdehyde were synthesized from [14C]-labelled phenol, guaiacol, and catechol with methyl dichloromethyl sulfide (CH3SCHCl2) under Friedel–Crafts alkylation conditions in dichloromethane at −78°C for 5 min (in the case of phenol and guaiacol) or at −20°C for 1 min (in the case of catechol), by rapid addition of SnCl4 to mixtures of the phenolic compound and CH3SCHCl2, followed by hydrolysis with HCl. Regioselective formylation (para to the –OH group) was achieved. The conversion rates were 96, 81, and 88% for 4-hydroxybenzaldehyde, vanillin, and protocatechualdehyde, respectively, and the yields of the recovered products after work-up amounted to 88, 75, and 83%, respectively. In the case of guaiacol, 17% of isovanillin was obtained as by-product. It was found that the presence of water or ethyl acetate in the reaction mixture, at a molar ratio of 60:1 (water:guaiacol) or 120:1 (ethyl acetate:guaiacol), had little influence on the yields under the reaction conditions. Factors influencing the yields are discussed in the study. Copyright © 2004 John Wiley & Sons, Ltd.
[均匀标记-14C]-标记的4-羟基苯甲醛、香草醛和原儿茶醛是由[14C]-标记的苯酚、愈创木酚和儿茶酚与甲基二氯甲基硫醚(CH3SCHCl2)在-78°C下于二氯甲烷中在弗里德尔-克拉夫茨烷基化条件下快速加入SnCl4至酚类化合物和CH3SCHCl2的混合物中,然后与HCl水解,反应时间为5分钟(对于苯酚和愈创木酚)或1分钟(对于儿茶酚)。实现了区域选择性甲酰化(对羟基基团)。4-羟基苯甲醛、香草醛和原儿茶醛的转化率分别为96%、81%和88%,处理后回收产物的产量分别为88%、75%和83%。对于愈创木酚,副产物异香草醛的产量为17%。研究发现,反应混合物中存在的水或乙酸乙酯,以60:1(水:愈创木酚)或120:1(乙酸乙酯:愈创木酚)的摩尔比,对反应条件下的产量影响不大。影响产量的因素在研究中进行了讨论。版权 © 2004 John Wiley & Sons, Ltd.