1,2-Dithiolane-3-pentanoic acid (D,L-thioctic acid) of the formula ##STR1## is prepared by a process comprising (a) reacting a 2-(3-alkylthiopropionyl)-cyclopentanone-1 of the formula ##STR2## where R is a C.sub.1 -C.sub.4 alkyl, phenyl or benzyl in aqueous alkaline solution at a temperature of about 20.degree. C. to about 90.degree. C. to form the corresponding carboxylic acid of formula VI ##STR3## (b) reacting the compound of formula VI with an alkyl mercaptan at a temperature between -20.degree. C. and 0.degree. C. to form the corresponding thioketal of formula VII ##STR4## (c) reacting the compound of formula VII with sodium in liquid ammonia at a temperature between -60.degree. C. and -10.degree. C. to form the 6,8-dimercaptooctanoic acid of formula VIII ##STR5## (d) reacting the 6,8-dimercaptooctanoic acid of formula VIII in alkaline solution with an iron (III) salt and oxygen to form the 1,2-dithiolane-3-pentanoic acid of formula IX, or in place of steps (a) through (c) reacting an acid of formula XII ##STR6## where R.sub.1 and R.sub.2 are hydrogen, C.sub.1 -C.sub.4 -alkyl, phenyl or benzyl, with the proviso that both R.sub.1 and R.sub.2 cannot be benzyl, with sodium in liquid ammonia at a temperature between -60.degree. C. and -10.degree. C. to form the corresponding 6,8-dimercaptooctanoic acid of formula VIII. The compounds of formulae VI, VII, XII are new.
1,2-二
硫杂
环戊酸(D,L-
硫辛酸)的结构式为##STR1##通过以下过程制备:(a)在
水性碱性溶液中,将结构式为##STR2##其中R为C.sub.1-C.sub.4烷基,苯基或苄基的2-(3-烷基
硫代丙酰)-
环戊酮-1与反应,反应温度约为20°C至90°C,形成相应的
羧酸,结构式为VI##STR3##(b)将结构式为VI的化合物与烷基
硫醇在-20°C至0°C的温度下反应,形成相应的
硫醚
缩醛,结构式为VII##STR4##(c)将结构式为VII的化合物与液
氨中的
钠在-60°C至-10°C的温度下反应,形成结构式为VIII的6,8-二
硫代辛酸##STR5##(d)将结构式为VIII的6,8-二
硫代辛酸在碱性溶液中与
铁(III)盐和
氧气反应,形成结构式为IX的1,2-二
硫杂
环戊酸;或者在步骤(a)至(c)之间,将结构式为XII的酸##STR6##其中R.sub.1和R.sub.2为氢,C.sub.1-C.sub.4-烷基,苯基或苄基,但R.sub.1和R.sub.2均不能为苄基,与液
氨中的
钠在-60°C至-10°C的温度下反应,形成结构式为VIII的相应的6,8-二
硫代辛酸。化合物VI、VII、XII的结构式是新的。