作者:G. Madegard、P. Mestre、P. Raimond、J-P. Noël
DOI:10.1002/jlcr.2580361203
日期:1995.12
2,2′4′-Trichloro-[ring U-14C]acetophenone 3 was the key intermediate of this synthesis patterned after the industrial route. An unexpected poor yield was observed during the preparation of 3 by the Friedel-Crafts reaction of chloroacetyl chloride with 1,3-dichloro-[U-14C]benzene 10, possibly the result of an isotope effect although this poor yield might be explained by other factors. Two routes were checked for the preparation of 1,3-dichloro-[U-14C]benzene 10. The action of CCL4 with 1,3-dinitro-[U-14C]benzene at 280°C was entailed with explosions. A safer route started from [U-14C]aniline via 2,4-dichloro-[ring U-14C]acetanilide. Friedel-Crafts reaction of 10 with acetyl chloride gave rise in 52% yield to 2′,4′-dichloro-[ring U-14C]acetophenone 16 which was brominated to 2-bromo-2′,4′-dichloro-[ring U-14C]acetophenone 17;17 was condensed with 2,2-(ethylenedioxy)ethylmagnesium bromide to compound 18; 18 was condensed with 1,2,4-triazole to 5 then successively treated with HCl:water:dioxane and 2,2,2-trifluoroethanol/HCl. Separation of the two diastereomers by medium pressure liquid chromatography. 7% overall radioactive yield from [U-14C]aniline. Radiochemical purity 99%.
2,2′4′-三氯-[环U-14C]苯乙酮3是这种仿照工业路线合成的关键中间体。在通过Friedel-Crafts反应将氯乙酰氯与1,3-二氯-[U-14C]苯10反应制备3的过程中,发现产率极低,这可能是同位素效应的结果,但产率低也可能是由其他因素造成的。在制备1,3-二氯-[U-14C]苯10的过程中,我们检查了两种路线。在280°C下,CCL4与1,3-二硝基-[U-14C]苯发生反应时发生了爆炸。一种更安全的路线是从[U-14C]苯胺出发,通过2,4-二氯-[环U-14C]乙酰苯胺。10与乙酰氯发生Friedel-Crafts反应,产率为52%,生成2′,4′-二氯-[环U-14C]苯乙酮16,后者被溴化为2-溴-2′,4′-二氯-[环U-14C]苯乙酮17;17与2,2-(乙撑二氧基)乙基溴化镁缩合生成化合物18;18与1,2