GB1574544A - Process for the preparation of halogeno-methylated diphenyl ethers - Google Patents

Description

(54) PROCESS FOR THE PREPARATION OF HALOGENOMETHYLATED DIPHENYL ETHERS (71) We, BAYER AKTIENGESELL SCHAFT, a body corporated organised and existing under the laws of Germany, of Leverkusen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a process for the preparation of certain mhalogenomethylated diphenyl ethers. In addition, the present invention relates to the conversion of the m - halogenomethylated diphenyl ethers thus obtained into the corresponding benzyl alcohols.

It has already been disclosed to prepare m - halogenomethylated diphenyl ethers by the side-chain halogenation of a methyl group of a corresponding diphenyl ether to give a halogenomethyl group. However, this process is technically involved (see DOS (German Published Specification) 2,402,457).

It has also been disclosed to prepare m bromomethylphenyl aryl ethers by brominating the corresponding phenyl aryl ether at temperatures above 180 C in the presence of UV light. This process is technically involved and gives products which are brominated in the ring and which necessitate increased expenditure on purification (see DOS (German Published Specification) 2,612,115).

It has also been disclosed to react m halogenomethylated diphenyl ethers, formed in the known halogenation processes, with alkali metal acetates and to saponify and, respectively, to reduce the acetic acid esters and the aldehydes thereby obtained to the corresponding benzyl alcohols. This process is carried out with relatively expensive acetates, which makes it uneconomical.

The present invention now provides a process for the preparation of an mhalogenomethylated diphenyl ether of the general formula

in which, X represents chlorine or bromine and R1-R4, which need not be identical, each represent hydrogen, halogen, alkyl (preferably with up to 4 carbon atoms), aryl, halogenoalkyl with 1--4 carbon atoms and up to 5 halogen atoms, cyano, nitro or alkoxycarbonyl, ifl which a compound of the general formula

in which R1-R4 have the meanings stated above, is halogenated in the presence of UV light, the reaction being carried out at a temperature up to 1000C, especially at from 0 to 1000C, and in the presence of a diluent.

The process according to the invention represents a substantial improvement compared with the processes known from the state of the art. It makes it possible to carry out the halogenation reaction to give the m- halogenomethylated diphenyl ethers at relatively low temperatures, which presents considerable industrial advantages, which are self-evident (for example saving in energy, less difficulty in choosing suitable reaction vessels and less corrosion by hydrogen halide).

It was decidedly surprising that the products, halogenated in the side chain, may be obtained from the compounds of the general formula (II) in good yield by the process according to the invention. This is contrary to the statements of the state of the art, according to which, even when accelerators for the side-chain halogenation, which proceeds via free radicals, are used (for example UV light), relatively large amounts of by-products, that is to say nuclear-halogenated compounds, are formed. According to the statements of the state of the art, the side-chain halogenation proceeds with good yields only when the reaction is carried out at temperatures above 220cm and in the presence of phosphorus halides (see DOS (German Published Specification) 2,402,457).

According to other statements, substantial amounts of ring-brominated products are obtained in the bromination of m - aryloxytoluenes in the presence of UV radiation below 1800C (see DOS (German Published Specification) 2,612,115). It was therefore even more surprising that the products, halogenated in the side chain, are obtained in high yields even at the low temperatures chosen according to the invention.

The compounds of the formula (II) employed as starting materials are known.

The following are particularly suitable: m methyldiphenyl ether, m - ethyldiphenyl ether, m - chloro - m - methyl - diphenyl ether, m - methyl - p' - chlorodiphenyl ether, m - methyl - p' - fluoro - diphenyl ether, m' - fluoro - m - methyldiphenyl ether, m - cyanomethyldiphenyl ether and m - dicyanomethyldiphenyl ether.

The process according to the invention is carried out in the presence of a diluent.

Suitable diluents include inert organic solvents, for example halogenohydrocarbons, such as carbon tetrachloride, tetrachloroethane, methylene chloride and tetrabromoethane. An excess of the diphenyl ether to be halogenated, of the general formula (II), can also be used as the diluent, especially in the case of the bromination.

Customary mercury lamps, for example the Philips HPK 125 W and Philips (trade mark) HTQ 700 mercury high pressure lamps, can be used as sources of ultraviolet radiation.

In a preferred manner of carrying out the process according to the invention, the diphenyl ether, of the general formula (II), that is to be reacted is brought, in a diluent, to the desired temperature by means of an immersed UV lamp, protected by a glass tube, and the required amount of halogen is introduced continuously into the reaction solution, for example via a frit in the floor of the reaction vessel. It is clear that different amounts of halogen are required, depending on the nature of the desired reaction product. Thus, the conversion into the predominantly monohalogenated ether of the general formula (I) is carried out by using approximately stiochiometric amounts of the reactants. In general, the halogen is reacted with 0.900.95 molar equivalent of the diphenyl ether of the general formula (II), in order to suppress the formation of undesired by-products.

However, an alternative procedure is to use an amount of halogen substantially less than the equivalent amount; in this variant the excess diphenyl ether is advantageously employed as the diluent. In some cases it is sufficient to prepare mixtures of monohalogenated and dihalogenated diphenyl ethers, for example mixtures of m - monochloromethyldiphenyl ether and m- dichloromethyldiphenyl ether, which can be employed for the further conversion to the m - hydroxymethyldiphenyl ether.

The hydrogen halide formed in the reaction of a diphenyl ether of the general formula (II) with halogen can be passed, using an inert gas, for example nitrogen, from the reaction vessel into an absorption device. The inert gas can also simultaneously be used here as a carrier for the halogen, for example in the halogenation with bromine.

The reaction can be carried out batchwise or continuously. Thus, in the continuous variant long reaction vessels are often used in order to extend the residence time of the reactants in the reaction chamber. It can be appropriate here to bring the diphenyl ether of the general formula (II), in a diluent, to the required reaction temperature before it is fed into the reaction vessel.

The rate of the halogenation of a diphenyl ether of the general formula (II) can be monitored, for example by analysis by gas chromatography. After the reaction has ended, the mixture can be worked up in various ways: thus it can be advantageous to free the reaction solution from hydrogen halide by washing with water and to isolate the reaction product by distillation under reduced pressure. However, sometimes the halogenation products are already obtained in such a pure form that they can be employed directly for further reactions.

By suitable control of the reaction, both m- monohalogenomethyldiphenyl ethers and mixtures of m - monohalogenomethyldiphenyl ethers and m - dihalogenomethyldiphenyl ethers and of m - dihalogeno methyldiphenyl ethers and m- trihalogenomethyldiphenyl ethers can be obtained using the process according to the invention.

As already mentioned, m - monohalogenomethyldiphenyl ethers, m dihalogenomethyldiphenyl ethers, mtrihalogenomethyldiphenyl ethers and mixtures of these compounds are obtained by the process according to the invention.

Both the individual compounds and the mixtures can be further converted into the corresponding m - hydroxymethyldiphenyl ethers, which are important intermediates for the preparation of insecticidally active compounds.

The invention thus also relates to a technically improved process for converting the m- halogenomethyldiphenyl ethers, and mixtures of these compounds, obtainable by the above-mentioned process into the corresponding m hydroxymethyl - diphenyl ethers.

Thus, it is already known to react m halogenomethyldiphenyl ethers, or mixtures thereof, with alkali metal acetates and to saponify and, respectively, to reduce the m - phenoxybenzyl acetates and mphenoxybenzaldehydes which are thereby formed individually or as mixtures. In this process, saponification and reduction can be carried out in different stages or simultaneously (see DOS (German Published Specification) 2,402,457).

The present invention also provides a process for the preparation of an mphenoxybenzyl alcohol of the general formula

in which R1-R4 have the meanings stated above, from an m - halogenomethyldiphenyl ether or from a mixture of the corresponding monohalogenomethyldiphenyl ethers, dihalogenomethyldiphenyl ethers and/or trihalogenomethyldiphenyl ethers, in which an m-halogenomethyldiphenyl ether prepared according to the present invention or a mixture of such ethers, is reacted with an alkali metal or alkaline earth metal salt of a carboxylic acid, optionally in the presence of a diluent (preferably a polar solvent), and the m- phenoxybenzyl ester or mphenoxybenzaldehyde, or a mixture thereof, formed is saponified (hydrolysed) and/or reduced.

Preferably, the compound (I), or a mixture of such compounds, reacted with an alkali metal formate in the presence of formic acid.

The advantage of this process compared with the process known from the state of the art (see DOS (German Published Specification) 2,402,457) is that it is possible, without being disadvantageous for the course of the reaction, to replace the costly alkali metal acetates by inexpensive alkali metal formates, which in some cases are obtained as waste products.

Preferred diluents are the diluents already mentioned in connection with the halogenation, and also inert organic solvents, such as formic acid, alcohols, such methanol or ethanol, ketones, such as acetone, ethers, such as tetrahydrofuran, dimethylsulphoxide or dimethylformamide.

The reaction is generally carried out at temperatures between room temperature and 100"C, preferably at the boiling point of the diluent used. The saponification and/or reduction of the m- phenoxybenzyl formate or m- phenoxybenzaldehyde, formed in the reaction with the alkali metal formate to give the corresponding mphenoxybenzyl alcohol can be effected by carrying out the reaction at room temperature for several hours in alcoholic solution and in the presence of a base and of a compound which reduces an aldehyde group to the corresponding alcohol group, such as sodium borohydride, or by carrying out the reaction under the conditions of the Cannizzaro reaction, using a base and formaldehyde, or by carrying out a catalytic hydrogenation, using a metal catalyst, such as Raney nickel or palladium, and a subsequent hydrolysis, or by first carrying out the reduction as described above then formylating the intermediate product with formic acid and sodium formate and subsequently saponifying the product.

If mixtures of m - dichloromethyldiphenyl ether and m - trichloromethyldiphenyl ether are reacted with sodium formate in dimethylformamide, the mixture of m - formylphenyl ether and m- carboxydiphenyl ether is obtained, from which the m - formyldiphenyl ether can be separated off as a stable bisulphite addition compound capable of storage. m Formyldiphenyl ether is obtained from this in a manner which is in itself known. This ether can be reduced as described above.

The preparative Examples which follow illustrate the process of the present invention.

Example 1 Preparation of m-monochloromethyldiphenyl ether 43.0 g (0.6 mol) of dry chlorine gas were passed into a solution of 184 g (1.0 mol) of m - phenoxytoluene in 1.1 litres of carbon tetrachloride, which was in a four-necked flask provided with a reflux condenser, internal thermometer, stirrer, gas inlet tube and immersion shaft, in the course of 1 hour at 80"C, whilst irradiating internally with UV light (HPK 125 W mercury high pressure lamp). A vigorous stream of nitrogen was then passed through the solution in order to expel undissolved hydrogen chloride. Evaporation of the solution under reduced pressure gave 204 g of a light brown oil.

Analysis by gas chromatography gave the following composition: 32.5 of mphenoxybenzyl chloride, 65% of mphenoxytoluene and 2.5% of other impurities.

This corresponded to a yield of m phenoxybenzyl chloride amounting to 87, relative to reacted m - phenoxytoluene.

Example 2 Preparation of a mixture of m-monohalogenomethyl- and m-dihalogenomethyldiphenyl ether 128 g (1.8 mol) of dry chlorine gas were passed into a solution of 184.0 g (1.0 mol) of m - phenoxytoluene in 1.1 litres of carbon tetrachloride in the course of 2 hours under the reaction conditions described in Example 1. A vigorous stream of nitrogen was then passed through the solution in order to expel dissolved hydrogen chloride.

Evaporation of the solution under reduced pressure gave 245.0 g of a light brown oil.

Analysis by gas chromatography gave the following composition: 38.8% of mphenoxybenzyl chloride, 53.4 /a of mphenoxybenzal chloride, 4.6% of mphenoxybenzotrichloride and 3.2% of unidentified by-products.

Example 3 Preparation of a mixture of m-dihalogenomethyl- and m-trihalogenomethyldiphenyl ether 184.0 g (1.0 mol) bf m-phenoxytoluene were reacted with 192.0 g (2.7 mol) of dry chlorine gas in the course of 3 hours under the reaction conditions indicated in Example 1. The crude reaction product obtained after working up had the following composition: 70.1% of m - phenoxybenzal chloride, 24.2 /a of m- phenoxybenzotrichloride and 5.7 /a of nuclear-chlorinated compounds.

Example 4 128.0 (0.8 mol) of bromine were added dropwise to a solution of 184.0 g (1.0 mol) of m - phenoxytoluene in 1.1 litres of carbon tetrachloride at 800C via a dropping funnel dripping into the reaction mixture, whilst stirring and whilst irradiating with a Philips HPK 125 W mercury high pressure lamp, so that the hydrogen bromide formed did not carry any bromine with it on leaving the reaction chamber. Analysis of the crude reaction product by gas chromatography gave the following composition: 34.5% of m - phenoxytoluene, 56.1% of v m phenoxybenzyl bromide, 7.5 /a of mphenoxybenzal bromide and 1.9% of nuclear - brominated compounds.

Fractional distillation on an active column gave 120.2 g of m - phenoxybenzyl bromide as a colourless oil of boiling point 104- 1050C/0.04 mm Hg.

The comparative Examples which follow show that variations in the process according to the invention lead to increased formation of nuclear-substituted products: Example A Halogenation of m-phenoxytoluene under conditions which were identical to those of the process according to the invention, but at the temperatures prescribed in DOS (German Published Specification) 2,612,115.

387.0 g (2.1 mol) of m - phenoxytoluene were warmed to 2250C in a 500 ml reaction vessel which was provided with a bromine feed tube, a Philips HPK 125 W mercury high pressure lamp, a reflux condenser and a gas outlet tube. The equivalent amount of bromine (100 ml) was added dropwise in the course of 1.5 hours, whilst irradiating with UV light. The mixture was then allowed to cool, whilst passing nitrogen through. The composition of the reaction mixture was determined by gas chromatography to be: 71.0% of m - phenoxybenzyl bromide, 13.1% of m - phenoxybenzal bromide, 5.0 j of m- phenoxytoluene and 10.9% of nuclear - brominated compounds.

Comparison with the process, according to the invention, of Figure 4 shows that a mixture had been formed which contained a considerably higher proportion of nuclearsubstituted compounds than the mixture of Example 4.

Example B Chlorination of m-phenoxytoluene, carrying out the reaction without a diluent.

184.0 g (1.0 mol) of m - phenoxytoluene were reacted with 128.0 g (1.8 mol) of dry chlorine gas for 2 hours, whilst irradiating with UV light, under the conditions described in Example 1, but without a diluent, Working up as described gave a crude product, and analysis of this by gas chromatography gave the following composition: 61.2% of 3 - phenoxy - 6 chloro - toluene, 9.8% of m - phenoxy toluene and 25.9% of more highly chlorinated compounds.

Virtually no m - phenoxybenzyl chloride and m - phenoxybenzal chloride had been formed.

The Examples which follow illustrate the preparation of phenoxy benzyl alcohols from the m - halogenomethyldiphenyl ethers obtained above.

Example 5.1 165.0 g of sodium formate and 250.0 g of formic acid were added to 260.0 g of the crude chlorination mixture obtained according to Example 2, and the mixture was then boiled under reflux for 8 hours.

Thereafter, 900 ml of water were added to the reaction mixture and the mixture was extracted with benzene. The benzene extract was washed with aqueous sodium bicarbonate solution, water and saturated aqueous sodium chloride solution and concentrated under reduced pressure. 190.0 g of a light yellow oil were thus obtained, analysis of which gave the following composition: 39.0% of m - phenoxybenzyl formate, 52.5% of m phenoxybenzaldehyde and 8.5% of unidentified products.

Example 5.2 190.0 g of the reaction mixture obtained according to Example 5.1 were dissolved in 700 ml of ethanol, and 300 ml of ethanol, which had been saturated beforehand with NaOH, were added. A total of 20.0 g of sodium borohydride were added in portions to this solution in the course of 6-7 hours at a temperature of 15--20"C, whilst stirring. 10% strength aqueous acetic acid was then added carefully to the reaction mixture in order to destroy unreacted sodium borohydride. The mixture was extracted with benzene, the benzene extract was washed successively with saturated sodium bicarbonate solution, water and saturated sodium chloride solution and thereafter was concentrated under reduced pressure. 155.0 g of a yellow oil were obtained, fractional distillation of which on a multi-tray column gave 130.0 g of mphenoxybenzyl alcohol of boiling point 122--124"C/0.09 mm Hg.

Example 6.1 200.0 g of anhydrous sodium acetate and 330.0 g of acetic acid were added to 265.0 g of the crude mixture obtained from 184.0 g of m- phenoxytoluene according to Example 3 and the mixture was then heated under reflux for 8 hours. 1 litre of water was added to the cooled solution and the mixture was extracted with benzene.

Washing the benzene phase with aqeuous sodium bicarbonate solution, water and saturated sodium chloride solution gave, after concentrating under reduced pressure, 201.2 g of a light yellow oil; after adding 50 ml of ether, 500 ml of 40% strength aqueous sodium bisulphite solution were added and the mixture was stirred for 3 hours at 90"C.

It was allowed to cool and the precipitate was filtered off, rinsed several times with ether and dried under reduced pressure.

140.0 g of the adduct of mphenoxybenzaldehyde and sodium bisulphite were thus obtained. 36.1 g of m phenoxybenzoic acid were obtained as colourless crystals from the combined filtrates after concentrating, and crystallising the residue from methanol/ether.

Example 7.1 7.0 g of anhydrous sodium formate were added to 27.0 g (0.1 mol) of the m phenoxybenzyl bromide, obtained according to Example 4, in 100 ml of dimethylformamide and the mixture was heated at the boil for 10 hours, whilst stirring. The sodium bromide which had precipitated was filtered off and the filtrate was concentrated under reduced pressure.

23.0 g of a yellow oil were obtained, which predominantly ( > 95%) consisted of mphenoxybenzyl formate.

Example 7.2 23.0 of the crude m - phenoxybenzyl formate obtained according to Example 7.1 were dissolved in 30 ml of ethanol, saturated with sodium hydroxide, a further 50 ml of ethanol were added and the mixture was stirred for 6 hours at 200 C. The reaction product was added to 300 ml of water and the mixture was extracted with benzene.

The benzene extracts were worked up as described in Example 3 and gave, on concentrating, 18.5 g of a yellowish oil, fractional distillation of which gave 14.1 g of m - phenoxybenzyl alcohol as a colourless oil of boiling point 108--1 10"C/0.05 mm Hg.

WHAT WE CLAIM IS: 1. A process for the preparation of a compound of the general formula

in which X represents chlorine or bromine and R1-R4, which need not be identical, each represent hydrogen, halogen, alkyl, aryl, halogenoalkyl with 14 carbon atoms and up to 5 halogen atoms, alkoxycarbonyl, cyano or nitro, in which a compound of the general formula

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. The Examples which follow illustrate the preparation of phenoxy benzyl alcohols from the m - halogenomethyldiphenyl ethers obtained above. Example 5.1 165.0 g of sodium formate and 250.0 g of formic acid were added to 260.0 g of the crude chlorination mixture obtained according to Example 2, and the mixture was then boiled under reflux for 8 hours. Thereafter, 900 ml of water were added to the reaction mixture and the mixture was extracted with benzene. The benzene extract was washed with aqueous sodium bicarbonate solution, water and saturated aqueous sodium chloride solution and concentrated under reduced pressure. 190.0 g of a light yellow oil were thus obtained, analysis of which gave the following composition: 39.0% of m - phenoxybenzyl formate, 52.5% of m phenoxybenzaldehyde and 8.5% of unidentified products. Example 5.2 190.0 g of the reaction mixture obtained according to Example 5.1 were dissolved in 700 ml of ethanol, and 300 ml of ethanol, which had been saturated beforehand with NaOH, were added. A total of 20.0 g of sodium borohydride were added in portions to this solution in the course of 6-7 hours at a temperature of 15--20"C, whilst stirring. 10% strength aqueous acetic acid was then added carefully to the reaction mixture in order to destroy unreacted sodium borohydride. The mixture was extracted with benzene, the benzene extract was washed successively with saturated sodium bicarbonate solution, water and saturated sodium chloride solution and thereafter was concentrated under reduced pressure. 155.0 g of a yellow oil were obtained, fractional distillation of which on a multi-tray column gave 130.0 g of mphenoxybenzyl alcohol of boiling point 122--124"C/0.09 mm Hg. Example 6.1 200.0 g of anhydrous sodium acetate and 330.0 g of acetic acid were added to 265.0 g of the crude mixture obtained from 184.0 g of m- phenoxytoluene according to Example 3 and the mixture was then heated under reflux for 8 hours. 1 litre of water was added to the cooled solution and the mixture was extracted with benzene. Washing the benzene phase with aqeuous sodium bicarbonate solution, water and saturated sodium chloride solution gave, after concentrating under reduced pressure, 201.2 g of a light yellow oil; after adding 50 ml of ether, 500 ml of 40% strength aqueous sodium bisulphite solution were added and the mixture was stirred for 3 hours at 90"C. It was allowed to cool and the precipitate was filtered off, rinsed several times with ether and dried under reduced pressure. 140.0 g of the adduct of mphenoxybenzaldehyde and sodium bisulphite were thus obtained. 36.1 g of m phenoxybenzoic acid were obtained as colourless crystals from the combined filtrates after concentrating, and crystallising the residue from methanol/ether. Example 7.1 7.0 g of anhydrous sodium formate were added to 27.0 g (0.1 mol) of the m phenoxybenzyl bromide, obtained according to Example 4, in 100 ml of dimethylformamide and the mixture was heated at the boil for 10 hours, whilst stirring. The sodium bromide which had precipitated was filtered off and the filtrate was concentrated under reduced pressure. 23.0 g of a yellow oil were obtained, which predominantly ( > 95%) consisted of mphenoxybenzyl formate. Example 7.2 23.0 of the crude m - phenoxybenzyl formate obtained according to Example 7.1 were dissolved in 30 ml of ethanol, saturated with sodium hydroxide, a further 50 ml of ethanol were added and the mixture was stirred for 6 hours at 200 C. The reaction product was added to 300 ml of water and the mixture was extracted with benzene. The benzene extracts were worked up as described in Example 3 and gave, on concentrating, 18.5 g of a yellowish oil, fractional distillation of which gave 14.1 g of m - phenoxybenzyl alcohol as a colourless oil of boiling point 108--1 10"C/0.05 mm Hg. WHAT WE CLAIM IS:

1. A process for the preparation of a compound of the general formula

in which X represents chlorine or bromine and R1-R4, which need not be identical, each represent hydrogen, halogen, alkyl, aryl, halogenoalkyl with 14 carbon atoms and up to 5 halogen atoms, alkoxycarbonyl, cyano or nitro, in which a compound of the general formula

in which R1-R4 have the meanings stated above, is halogenated in the presence of UV light, the halogenation being carried out at a temperature up to 1000C and in the presence of a diluent.

2. A process according to claim 1, in which the halogenation is effected at from 0 to 1000C.

3. A process according to claim 1 or 2, in which the halogenation is effected using elementary chlorine or elementary bromine.

4. A process according to claim 1, 2 or 3, in which the compound (II) is selected from m - methyldiphenyl ether, m ethyldiphenyl ether, m - chloro - m - methyl - diphenyl ether, m - methyl - p' chlorodiphenyl ether, m - methyl - p' fluorodiphenyl ether, m' - fluoro - m - methyldiphenyl ether, m cyanomethyldiphenyl ether and mdicyanomethyldiphenyl ether.

5. A process according to claim 4, in which m - methyldiphenyl ether is used as the starting compound (II).

6. A process according to any of claims 1 to 5, in which the diluent is an inert organic solvent.

7. A process according to claim 6, in which the diluent is a halogenohydrocarbon.

8. A process according to claim 7, in which the halogenation is carried out in carbon tetrachloride at 80at.

9. A process according to any of claims 1 to 5, in which a bromination is effected and an excess of the starting compound of the general formula (II) is used as the diluent.

10. A process according to any of claims 1 to 9 in which a mixture of compounds of the formula (I) is prepared.

I 1. A process according to claim 1, substantially as described in any one of Examples 1 to 4.

12. Compounds of the formula (I) given in claim 1, whenever prepared by a process according to any of claims 1 to 10.

13. A process for the preparation of an m- hydroxymethyldiphenyl ether of the general formula

in which R1-R4 have the meanings stated in claim 1, in which a compound according to claim 12, or a mixture of such compounds, is reacted with an alkali metal salt or alkaline earth metal salt of a carboxylic acid, optionally in a polar solvent, and the product is then hydrolysed and/or reduced.

14. A process according to claim 13, in which the compound according to claim 12, or the mixture of such compounds, is reacted with an alkali metal formate in formic acid and, the product is then hydrolysed and/or reduced.

15. A process according to claim 13 substantially as described in Examples 5.1 and 5.2 or in Examples 7.1 and 7.2.

16. Compounds of the formula (III) given in claim 13, whenever prepared by a process according to claim 13, 14 or 15.