Claims
- 1. An improved process for the manufacture of an enantiomeric form of a compound of formula I
- wherein R.sub.a is (2-12C)alkyl, or naphthylmethyl or cinnamyl optionally bearing one or two halogeno substituents, or benzyl optionally bearing one or two substituents independently selected from halogen, (1-4C)alkyl, (1-4C)alkoxy, cyano, nitro and trifluoromethyl located in the 2-, 3-, 4- or 5-position of the phenyl moiety; benzene ring A optionally bears one or two substituents independently selected from halogeno, (1-4C)alkyl, trifluoromethyl and nitro; and Q is methylene or imino; but R.sub.a is other than ethyl, n-propyl or unsubstituted benzyl when benzene ring A is unsubstituted and Q is imino; which comprises carrying out the known steps of:
- (a) forming a diastereoisomeric mixture of salts between a racemic form of said compound and an optically active form of a suitable quaternary ammonium base;
- (b) separating the mixture of salts obtained in (a) by fractional crystallisation from a suitable solvent to give a crystalline salt and a mother liquor; and
- (c) liberating said required enantiomeric form of the compound of formula I from the crystalline salt obtained in (b) by acidification; and is characterised by carrying out the additional steps of:
- (d) liberating the mixture of enantiomeric forms of the compound of formula I by acidification of the salts in the mother liquor obtained in (b);
- (e) heating the mixture of enantiomeric forms of the compound of formula I obtained in (d) at a temperature in the range 80.degree. to 280.degree. C., to give the racemic form of said compound; and
- (f) recycling the racemic form obtained in (e) in the salt formation step (a).
Parent Case Info
This is a division of application Ser. No. 593,312 filed Mar. 26, 1984, now U.S. Pat. No. 4,567,278.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
2743284 |
Klein et al. |
Apr 1956 |
|
3024231 |
Scherrer |
Mar 1962 |
|
Non-Patent Literature Citations (1)
Entry |
Gilman, H. et al., (Editors) Organic Chemistry, John Wiley, New York, 1938, pp. 176-177. |
Divisions (1)
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Number |
Date |
Country |
Parent |
593312 |
Mar 1984 |
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