# US 5,347,020 A · Process for the preparation and purification of thermolabile compounds

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- Number: US 5,347,020 A
- Document ID: US5347020A
- Status: Granted
- Kind: A
- Application number: 08/013,517
- Filed: 1993-02-03
- Granted: 1994-09-13
- Earliest claimed: 1986-10-24
- Assignees: Boehringer Ingelheim GmbH
- Inventors: Michael Aigner; Wolfgang Dersch; Dieter Reichert; Horst Schwall; Werner Warth
- Web page: https://patentgrep.com/patent/US5347020A

## CPC

- C07D 319/12: not condensed with other rings
- B01J 19/20: in the form of helices, e.g. screw reactors
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS

## Abstract

The invention relates to a new process for the preparation and purification of thermolabile compounds.

## Claims

### Claim 1

A process for the preparation of a glycolide of the general formula ##STR2## wherein R.sub.1 and R.sub.2 independently of one another are hydrogen or a branched or unbranched alkyl radical with up to 16 carbon atoms, from the corresponding low molecular weight poly-.alpha.-hydroxycarboxylic acid or an .alpha.-halogenocarboxylic acid salt in the presence of a catalyst, wherein the starting compound is subjected to thermolysis which is carried out continuously under forced conveyance in a reactor with a rising temperature gradient, and the glycolide formed is distilled off.

### Claim 2 (depends on 1)

The process according to claim 1, wherein the temperature gradient rises from about 15.degree. to 280.degree. C. and thermolysis is carried out under a reduced pressure between about 0.1 to 5 mbar.

### Claim 3 (depends on 2)

The process for the preparation of 1,4-dioxane-2,5-dione according to claim 2, wherein low molecular weight polyglycolides or halogenoacetic acid salts are used as the starting compound.

### Claim 4

Poly-(1,4-dioxane-2,5-dione), having an intrinsic viscosity of 1.4 [dl/g], measured in hexafluoroisopropanol at 30.degree. C.