Process for the preparation of urethanes
View Patent ↗Urethanes are prepared by oxidative carbonylation of at least one amino compound in the presence of carbon monoxide, oxygen and organic, at least one hydroxyl-group-carrying compound. The carbonylation is carried out in the absence of halogen-containing promoters. The carbonylation is also carried out in the presence of a metal complex catalyst which contains neutral bidentate N-chelate ligands of the (N˜N) type, two monoanionic N,O-chelate ligands of the general type (N˜O) − or tetradentate dianionic chelate ligands (O˜N˜N˜O) 2− .
1. An industrial process for the preparation of a urethane by oxidative carbonylation of an amino compound in the presence of carbon monoxide, oxygen and an organic, hydroxyl-group-carrying compound, comprising carrying out the carbonylation in the absence of a halogen-containing promoter and in the presence of a metal complex catalyst comprising a metal complex catalyst of formula scheme V or, wherein:
formula scheme V is:
in which:
[Co] represents cobalt in its divalent oxidation state;
R 1 represents hydrogen, an alkyl radical having from 1 to 20 carbon atoms, an aryl or heteroaryl group, a OR group in which R represents hydrogen or an alkyl group having from 1 to 20 carbon atoms, or NRR′ in which R and R′ represent hydrogen or each represent an aryl or alkyl group having from 1 to 20 carbon atoms, or R and R′ together can form a ring system containing a nitrogen atom as heteroatom;
R 2 represents hydrogen, an alkyl group having from 1 to 20 carbon atoms, an aryl group or heteroaryl group which is linked via one or two C˜C bonds fused to the salicylate structural unit, a keto group —COR or —COOR, —COOH, fluorine, chlorine, bromine, iodine, OH, OR or NRR′, and R 2 can substitute the aromatic ring from 1 to 4 times.; in OR, —COR, and —COOR, R represents hydrogen or an alkyl group having from 1 to 20 carbon atoms, and in NRR′, R and R′ represent hydrogen or each represent an aryl or alkyl group having from 1 to 20 carbon atoms, or R and R′ together can form a ring system containing a nitrogen atom as heteroatom;
X represents any of the aryiene or alkylene structural units, which links the two imino nitrogen atoms with one another; and
wherein the carbonylation is carried out in an aliphatic or aromatic alcohol at a temperature of from 80 to 260° C. under an absolute carbon monoxide pressure of from 10 to 100 bar and an absolute oxygen pressure of from 1 to 10 bar, and
wherein the carbonylation is carried out in the absence of a halogenated solvent.
2. The industrial process of claim 1 , wherein the metal complex catalyst is used in a concentration of from 0.1 to 10 mol %, based on one mole of amino groups.
3. The industrial process of claim 1 , wherein the carbonylation is carried out in methanol, ethanol, or n-butanol.
4. The industrial process of claim 1 , wherein ureas groups are formed during the carbonylation, wherein these urea groups subsequently react further, partially or completely, with the organic hydroxyl-group-containing compound by alcoholysis to give the corresponding urethanes.
5. The process of claim 1 in which an aliphatic, cycloaliphatic and/or aromatic mono- OF di-amino compound is used.
6. An industrial process for the preparation of isocyanates, comprising:
a) preparing a urethane by carbonylation by the process of claim 1 , and
b) thermally cleaving the urethane to obtain the isocyanate.
7. The industrial process of claim 6 , wherein the carbonylation and the thermal cleavage take place in one process step.