The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 30, 1990
Filed:
Jul. 15, 1987
Guenes Giray, Kleinostheim, DE;
Klaus Huthmacher, Gelnhausen, DE;
Axel Kleemann, Muhlheim, DE;
Thomas Lied, Obertshausen, DE;
Degussa Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
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 temperature temperture between -60.degree. C. and -10.degree. C. to form the 6,8-dimercaptooctanic acid of formual 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.