Process for preparing 2-methoxycarbonylmethyl-6,6-dimethyl-2-tetrahydropyran carboxylic acid (I) comprising:
a) Reaction of 5-bromo-2-methyl-2-pentene (III) with magnesium and then diethyloxalate to obtain ethyl-2-oxo-6-methyl-5-heptenoate (IV);
b) Reaction of ethyl-2-oxo-6-methyl-5-heptenoate (IV) with an alkali amide and methyl acetate to obtain ethyl-2-methoxycarbonylmethyl-2-hydroxy-6-methyl-5-heptenoate (V);
c) Reaction of ethyl-2-methoxycarbonylmethyl-2-hydroxy-6-methyl-5-heptenoate (V) with an alkali metal hydroxide to obtain the corresponding 2-carboxymethyl-2-hydroxy-6-methyl-5-heptenoic acid (VI);
d) Cyclisation of 2-carboxymethyl-2-hydroxy-6-methyl-5-heptenoic acid (VI) with formic acid to give 2-carboxymethyl-6,6-dimethyl-2-tetrahydropyrancarboxylic acid (VII);
e) Monoesterification of 2-carboxymethyl-6,6-dimethyl-2-tetrahydropyrancarboxylic acid (VII) to 2-methoxycarbonylmethyl-6,6-dimethyl-2-tetrahydropyran carboxylic acid (I),
characterised in that in stage (e) the 2-methoxycarbonylmethyl-6,6-dimethyl-2-tetrahydropyran carboxylic acid (I) is purified by means of the formation of the corresponding salt with cyclohexylamine (IA).
制备2-甲氧羰基甲基-6,6-二甲基-2-
四氢吡喃羧酸(I)的过程包括:
a)将
5-溴-2-甲基-2-戊烯(III)与
镁反应,然后与
草酸二乙酯反应,得到
乙酸乙酯-2-氧代-6-甲基-5-
庚烯酸酯(IV);
b)将
乙酸乙酯-2-氧代-6-甲基-5-
庚烯酸酯(IV)与碱
金属酰胺和
乙酸甲酯反应,得到
乙酸乙酯-2-甲氧羰基甲基-2-羟基-6-甲基-5-
庚烯酸酯(V);
c)将
乙酸乙酯-2-甲氧羰基甲基-2-羟基-6-甲基-5-
庚烯酸酯(V)与碱
金属氢氧化物反应,得到相应的2-羧甲基-2-羟基-6-甲基-5-
庚烯酸(VI);
d)将2-羧甲基-2-羟基-6-甲基-5-
庚烯酸(VI)与
甲酸环化,得到2-羧甲基-6,6-二甲基-2-
四氢吡喃羧酸(VII);
e)将2-羧甲基-6,6-二甲基-2-
四氢吡喃羧酸(VII)进行单酯化反应,得到2-甲氧羰基甲基-6,6-二甲基-2-
四氢吡喃羧酸(I),其特征在于在阶段(e)中,通过与
环己胺(IA)形成相应的盐来纯化2-甲氧羰基甲基-6,6-二甲基-2-
四氢吡喃羧酸(I)。