申请人:Pfizer Inc.
公开号:US04471139A1
公开(公告)日:1984-09-11
Processes for preparing isomerically pure 3-methylthiophene-2-carboxaldehyde, an intermediate for synthesis of anthelmintic agents, by reaction of mercaptoacetaldehyde or the dimer, or a polymer thereof, or a dialkylacetal thereof in the presence of a base with (1) methyl vinyl ketone or an alpha- or beta-oxidized derivative of methyl vinyl ketone to form a 3-oxobutylmercaptoacetaldehyde or dialkyl acetal thereof, or an alpha- or beta-substituted derivative thereof which is then converted to 3-methylthiophene-2-carboxaldehyde via appropriate steps including, if necessary, treatment with acid, followed, if necessary, by enamine catalyzed cyclization and, in the case of using methyl vinyl ketone as reactant, a dehydrogenation step; or (2) 3-butyn-2-one to produce a mixture of isomeric 3-oxobut-1-enylmercaptoacetaldehyde or dialkyl acetals thereof which is cyclized to 3-methylthiophene-2-carboxaldehyde. A further aspect of this invention is an improved process for making dialkyl acetals of 2-mercaptoacetaldehyde which comprises reacting an alkyl vinyl ether with sulfur chloride to produce a bis(2-chloro-2-alkoxy ethyl)disulfide which is then treated with an alcohol to afford a bis(2,2-dialkoxyethyl)disulfide which is reduced under alkaline conditions to 2-mercaptoethyl acetaldehyde alkali metal salt which can be alkylated to a thioether, a valuable intermediate.
制备异构纯3-甲基硫代呋喃-2-甲醛的方法,这是合成驱虫剂的中间体,通过在碱的存在下,将巯基乙醛或其二聚体或聚合物,或其二烷基乙醛与(1) 甲基乙烯酮或甲基乙烯酮的α-或β-氧化衍生物反应,形成3-氧代丁基巯基乙醛或其二烷基缩醛,或其α-或β-取代衍生物,然后通过适当的步骤转化为3-甲基硫代呋喃-2-甲醛,包括必要时用酸处理,接着必要时用烯胺催化环化,如果使用甲基乙烯酮作为反应物,则进行脱氢步骤;或(2) 3-丁炔-2-酮与之反应,产生异构的3-氧代丁-1-烯基巯基乙醛或其二烷基缩醛混合物,再环化成3-甲基硫代呋喃-2-甲醛。此外,本发明的另一个方面是制备2-巯基乙醛的二烷基缩醛的改进方法,包括将烷基乙烯醚与硫氯化物反应,产生双(2-氯-2-烷氧基乙基)二硫化物,然后用醇处理得到双(2,2-二烷氧基乙基)二硫化物,在碱性条件下还原为2-巯基乙基乙醛碱金属盐,可以烷基化为硫醚,这是一种有价值的中间体。