GB2245563A

GB2245563A - Preparation of 3-dialkylaminophenols

Info

Publication number: GB2245563A
Application number: GB9113275A
Authority: GB
Inventors: Manfred Hauptreif; Helmut Reichelt
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1990-06-23
Filing date: 1991-06-19
Publication date: 1992-01-08
Anticipated expiration: 2011-06-19
Also published as: GB2245563B; FR2663632A1; FR2663632B1; GB9113275D0; CH681888A5; JPH04230249A

Abstract

The formation of dealkylation products in the preparation of 3-dialkylaminophenols by reacting resorcinol with dialkylamines is reduced by carrying out the reaction in the presence of an ester of phosphorous acid and optionally also in the presence of phosphorous acid.

Description

k Preparation of 3-Dialkylaminophenols The present invention relates to a

method of reducing the formation of dealkylation products during the manufacture of 3-dialkylaminophenols involving the reaction of resorcinol with dialkylamines carried out in the presence of an ester of phosphorous acid and possibly also in the 5 presence of phosphorous acid.

A frequently observed side reaction occurring during the reaction of resorcinol with a dialkylamine is dealkylation. As a result, the effluent contains not only the desired product 3-dialkylaminophenol, but usually also 10 a relatively large amount of the dealkylation product 3monoalkylaminophenol.

It is an object of the present invention to provide a method of effectively reducing the formation of dealkylation products during the reaction of is resorcinol with dialkylarnines.

We have found that the formation of dealkylation products during the preparation of a 3-dialkylaminophehol of formula (1) OH LN / R1 \ R2 (1), in which R' and R2 are the same or different and denote, independently of each other. a Cl-C8-alkyl radical, by reacting resorcinol with an amine of formula (11) R' HN / (11), \ R 2 in which R' and R2 have the meanings stated above, at a temperature of from 1800 to 2500C and a pressure of from 10 to 40 bar, is effected in advantageous manner by carrying out the reaction in the presence of an ester of phosphorous acid and optionally also in the presence of phosphorous acid.

z 2 o.z.ooso/41681 The use of phosphorous acid or an ester thereof in the reaction of resorcinol with a cyclic secondary amine is described in DE-A 2,900,193, the purpose of the phosphorous acid or its ester being to suppress the formation of N,N'-disubstituted phenylene diamines and tarry residues. The reaction of resorcinol with cyclic secondary amines involves virtually no dealkylating side reactions.

It has thus been surprising to observe that the presence of an ester of phosphorous acid and optionally also of phosphorous acid can effectively suppress the formation of dealkylation products in the reaction of resorcinol with dialkylamines.

The alkyl radicals R' and R2 in formula (1) may be linear or branched, and examples thereof are: methyl, ethyl, propyl, isopropyl, butyl, isobuty], s- is butyl, pentyl, isopentyl, neopentyl, hexyi, 2-methylpentyl, heptyl, 2methylhexyl, octyl, 2-methyihepty], and 2-ethyihexyi.

It is preferred to carry out the reaction with an amine of formula (11) in which R' and 112 are independently Cl-C4-alkyl, particularly ethyl or butyl.

Suitable phosphorous acid esters -for use in the process of the invention are, for example, triphenyl phosphite or Cl-C8-trialkyl phosphites such as trimethyl phosphite, triethyl phosphite, tripropyl phosphite, thisopropyl phosphite, tributyl phosphite, triisobutyl phosphite, tri-s- butyl phosphite, tripentyl phosphite, trilsopentyl phosphite, trineopentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, and tris(2 -ethyl hexyl) phosphite.

It is preferred to use a phosphorous acid ester together with phosphorous acid.

It is further preferred to carry out the reaction in the presence of triphenyl phosphite or a Cl-C8-trialkyl phosphite.

The use of triphenyl phosphite or a Cl-C4-trialkyl phosphite is particularly preferred.

The process of the invention may be carried out batchwise or continuously and is advantageously carried into effect by heating a mixture of resorcinol, amine (11), possibly a diluent, the phosphorous acid ester, and possibly 3 c).z.coso/41681 phosphorous acid in a pressure vessel under autogenous pressure or in the presence of added inert gas (eg nitrogen) to a temperature of from 1800 to 2500C and preferably from 1901) to 2100C. The pressure in the vessel is usually from 10 to 40 bar, preferably from 20 to 40 bar, and more 5 preferably from 30 to 35 bar.

On completion of the reaction, which generally takes from 10 to 20 hours, the reaction mixture is cooled and depressurized.

The target product can then be isolated from the mixture in conventional manner, for example by dissolution in an acid, filtration and precipitation of the filtrate with, say, soda solution. Alternatively, the molten reaction mixture may be worked up by treatment with an organic non-polar solvent followed by removal of precipitated resorcinol by filtration and distillation of 15 the filtrate after the solvent has been removed.

The amount of phosphorous acid ester used is usually from 5% to 20% wlw, and preferably from 10% to 15% wlw, and more preferably about 10% wlw, based on the weight of resorcinoi used.

If the reaction is carried out in the presence of a phosphorous acid ester and phosphorous acid, the amount of the latter will usually be from 5% to 10% wlw, based on the weight of resorcinol used.

The molar ratio of amine (11) to resorcinol required for optimum conversion is generally from 1:2 to 2:1 and preferably from 1.1 to 1.2.1.

Alternatively, the reaction may be carried out using a larger excess of amine (11), in which case the excess amine (11) serves as a diluent.

Other diluents which may be used include organic solvents such as toluene and xylene.

It is preferred to carry out the process of the invention in the absence of 35 solvent.

The use of our novel process makes it possible to produce 3dialkylaminophenols of formula I in good yields. The amount of 3monoalkylaminophenol present in the effluent is distinctly reduced by the presence of 40 phosphite and, possibly, phosphorous acid.

9 4 o.z.ooso/41681 The 3-dialkylaminophenols of formula (1) are important intermediates for the synthesis of fluoranes, which are useful as color formers (cf. US-A 3, 873,573 for example). The invention is illustrated below by the following Examples.

Example 1 g of resorcinol, 56 mi of diethylamine, and 5.5 mi of triphenyl phosphite were heated in an autoclave at a temperature of 2000C for 15 hours under a blanket of nitrogen, during which time the pressure rose from its initial value of 10 bar to a final value of 25 bar. The reaction mixture was then cooled and depressurized.

There were obtained 96 g of a reaction mixture in which the ratio of is resorcinol to 3-diethylaminophenol to 3-monoethylaminophenot was 29:63:8, as determined by gas-chromatographic analysis.

Example 2 (Comparative Example) Example 1 was repeated except for the inclusion of triphenyl phosphite. The final pressure was 35 bar. There were obtained 91 g of a reaction mixture in which the ratio of resorcinol to 3-diethylaminophenol to 3monoethylaminophenol was 26.5:60:13.5, as determined by gas- chromatographic analysis.

Example 3

A mixture of 110 g of resorcinol, 76.6 g of diethylamine, 22 g of triphenyl phosphite and 11 9 of phosphorous acid were heated in an autoclave at a temperature of 19511C for 20 hours under a blanket of nitrogen, during which time the pressure rose from its initial value of 10 bar to a final value of 25 bar. The reaction mixture was then cooled and depressurized.

There were obtained 210 g of a reaction mixture in which the ratio of 3s resorcinol to 3-diethylaminophenol to 3-monoethylaminophenol was 28:53:0, as determined by gas-chromatographic analysis.

Example 4

Example 3 was repeated except that only 11 g of triphenyl phosphite and, Y 1 , ' 'I wg t o.z.ooso/41681 as catalyst, 5.5 g of phosphorous acid were used. There were obtained 195 g of a reaction mixture in which the ratio of resorcinol to 3diethylaminophenol to 3-monoethylaminophenol was 17.5:54.9:5.6, as determined by gas-chromatographic analysis.

Example 5

A mixture of 110 g of resorcinol, 76.6 g of diethylamine, 11 g of triethyl 10 phosphite and 5 g of phosphorous acid were heated in an autoclave at a temperature of 2100C for 15 hours under a blanket of nitrogen, during which time the pressure rose from its initial value of 10 bar to a final value of 25 bar. The reaction mixture was then cooled and depressurized.

There were obtained 193 g of a reaction mixture in which the ratio of resorcinol to 3-diethylaminophenol to 3-monoethylaminophenol was 41.9:55. 5:0 as determined by gas-chromatographic analysis.

Claims

1. A method of reducing the formation of dealkylation products in the preparation of a 3 -dialkylaminophenol of f ormula (I) OH R1 N 1.1 %" R2 (I) in which R1 and R2 are the same or different and independently denote Cl- C8-alkyl, by a process comprising the reaction of resorcinol with an amine of formula (II) R1 HN is \ R2 (II) in which R1 and R2 have the meanings stated above, at a temperature of from 180 to 250C and under a pressure of from 10 to 40 bar, wherein the said reaction is carried out in the presence of an ester of phosphorous acid.

2. A process as claimed in claim 1, wherein the reaction is carried out in the presence of an ester of phosphorous acid and also in the presence of phosphorous acid.

3. A process as claimed in claim 1 or 2, wherein the reaction is carried out in the presence of triphenyl phosphite or a Cl-C8- trialkyl phosphite as ester of phosphorous acid.

4. A process as claimed in any of claims 1 to 3, wherein in the formulae (1) and (II) R1 and R2 are independently ethyl or butyl.

5. A process as claimed in any of claims 1 to 4, in which the reaction is carried out in the presence of 10 to h 1; - 7 15% w/w of an ester of phosphorous acid and, where present, 5 to 10% w/w of phosphorous acid.

6. An improved process for the production of a 3dialkylaminophenol carried out substantially as hereinbef ore 5 described or illustrated in any of Examples 1, 3, 4 or 5.

7. 3-Dialkylaminophenols when produced by the use of a process as claimed in any of claims 1 to 6.

Published 199 1 at 7be Patent Office. Concept House. Cm-liff Road. Newport. Gwent NP9 1RH. Further copies mky be obtained from Sales Branch. Unit 6, Nine Mile Point. Cwrnfelinfach. Cross Keys. Newport. NP I 7H7-. Printed by Multiplex techniques ltd. St Mary Cray, Kent.