DE2503736A1 - 2-Oxo-quinazoline derivs prepn - by reacting 2-dichloromethyl-phenyl isocyanates with ammonia and cyclizing - Google Patents

Abstract

2-Oxo-quinazoline derivs. of formula (I)-(where X is halogen and n is 0,1,2,3 or 4) e.g. 2-oxo-1,2-dihydroquinazoline or 6-chloro-2-oxo-1,2-dihydroquinazoline, are prepared by reacting isocyanates for formula (II) with NH3 and cyclising the resulting inter. (which need not be isolated) with eliminated of HCl. (I) are useful as inters., e.g. for pharmaceuticals or plant protection agents. Thus (I) can be converted into 2-aminoquinazolines with bactericidal or microbicidal properties, pharmacological properties, or antioxidant properties. The process requires short reaction times and gives (I) in high yields without side-reactions.

Description

Process for the preparation of 2-oxo-1, 2-dihydro-quinazolines Die The invention relates to a new process for the preparation of 2-oxo-1,2-dihydro-quinazolines.

For the production of 2-oxo-1,2-dihydro-quinazoline, also known as 2-hydroxy-quinazoline or quinazolone- (2), two processes have become known so far. According to B. 28, p. 1037 (1895) and B. 29, p. 1313 (196), 2-aminobenzaldehyde is used with Excess urea heated to 150 to 155 ° C. According to R. 80, pp. T49 to 157 (1961) - the potassium salt of isatic acid is heated with urea to 130 to 140 ° C and the resulting quinazolone-4-carboxylic acid by boiling in water for several hours decarboxylated.

Both processes are designed to be carried out on an industrial scale not suitable because the starting compounds required in addition to urea are not easy accessible and the required reaction times are long and sometimes larger amounts By-products are obtained.

It has now been found that 2-oxo-1,2-dihydro-quinazolines of the formula in which X represents halogen and n represents one of the numbers 0, 1, 2, 3 or 4, if 2-dichloromethylphenyl isocyanates of the formula are obtained in which X and n are as defined above, are reacted with ammonia and the resulting reaction product is cyclized, optionally without intermediate isolation, with elimination of hydrogen chloride to give 2-oxo-1,2-dihydroquinazoline.

Halogen is fluorine, chlorine, bromine, iodine, preferably chlorine and bromine, especially called chlorine.

Using the example of 2-dichloromethylphenyl isocyanate, the process according to the invention is illustrated by the following equation: The 2-dichloromethyl-phenyl isocyanates of the formula II, which can be used as starting compounds in the process according to the invention, can be obtained by side-chain chlorination of 2-methylphenyl isocyanates by known processes (DT-PS 947 470; DT-OS 1 002 327), for example by chlorination 100 to 1500C can be obtained under UV exposure. The 2-methylphenyl isocyanates required for this are known or can be prepared by known methods.

Examples of starting compounds of the formula II are: 2-dichloromethyl-phenyl isocyanate 3-chloro-2-dichloromethyl-phenyl isocyanate 4-chloro-2-dichloromethyl-phenyl isocyanate 4-bromo-2-dichloromethyl-phenyl isocyanate 5-chloro-2-dichloromethyl-phenyl isocyanate 6-chloro-2-dichloromethyl-phenyl isocyanate 4,6-dichloro-2-dichloromethyl-phenyl isocyanate 3,4,6-trichloro-2-dichloromethyl-phenyl isocyanate tetrachloro-2-dichloromethyl-phenyl isocyanate In the inventive reaction of the 2-dichloromethylphenyl isocyanate Formula II with ammonia is the corresponding N- (2-dichloromethylphenyl) urea of the formula as the reaction product in which X and n have the meaning given above, obtained which is cyclized to the 2-oxo-1,2-dihydro-quinazoline of the formula I in a further reaction step with elimination of hydrogen chloride.

The process according to the invention can be carried out in various ways will.

According to a variant of the process according to the invention, the reaction preferably in the presence of an inert diluent in a one-pot process carried out so that the 2-dichloromethyl-phenyl isocyanate of the formula II with at least the stoichiometrically required amount of 3 mol of ammonia is converted.

In particular, these have proven to be expedient as diluents proved that the reaction product of the first stage, the N- (2-dichloromethyl-phenyl) -urea keep the formula III in solution. Ketones and cyclic ones are preferred as such ether such as dioxane and tetrahydrofuran called. Also mixtures of these solvents with water can be used when the 2-dichloromethyl-phenyl isocyanates of Formula II be added in mixtures of these solvents with water and ammonia.

When carrying out the method according to the invention in the absence of Water can also reverse the ammonia to 2-dichloromethylphenyl isocyanate of formula II come into effect.

In this variant, the process according to the invention is carried out in the temperature range between 200 and + 1500C, preferably in the temperature range between 0 ° and 100 ° C carried out.

In general, the first stage of the reaction is exothermic; therefore it can be useful, especially in the temperature range between 0 and 400C to run, for which cooling of the reaction mixture may be advantageous can be.

By subsequent heating to a higher temperature within of the specified temperature range may result in a faster expiry of the second reaction step can be achieved.

In general, the process according to the invention is carried out under normal pressure carried out; however, it can also be advantageous under increased pressure, e.g. in the closed Vessel under the increased autogenous pressure of the reaction components and the solvent at the reaction temperature.

In general, the isolation of 2-oxo-1,2-dihydroquinazoline of formula I can be carried out simply in a known manner; because the 2-oxo-1,2-dihydro-quinazolines of the formula I are sparingly soluble in many solvents, they generally fall from the reaction mixture and can be removed e.g. by filtration or centrifugation isolate and wash with water or a solvent in a conventional manner easy to clean.

The reaction scheme above is for the implementation of 2-dichloromethylphenyl isocyanate of the formula II to the N- (2-dichloromethylphenyl) urea of the formula III at least the stoichiometrically required amount of 1 mol of ammonia is necessary, while the remaining two moles of ammonia to bind the released during the cyclization Hydrogen chloride are required. It is therefore preferable to work with at least 3 mol of ammonia or an excess of up to 10, preferably up to 4 mol.

However, you can modify this variant of the invention Process for binding the in the cyclization of the N- (2-dichloromethylphenyl) urea of the formula III to the 2-oxo-1,2-dihydro-quinazoline part of the ammonia necessary as well replace with other hydrogen chloride binding agents.

As -such can e.g. be used: Alkali and Brdalkali-Oxydè, hydroxides and carbonates such as sodium, potassium, barium and calcium hydroxide, barium, Magnesium and calcium oxide, sodium, potassium, calcium and magnesium and parium carbonate, Heavy metal carbonates such as copper carbonate, zinc carbonate, cadmium carbonate, lead carbonate, Manganese carbonate, nickel carbonate.

Tertiary amines such as pyridine, triethylamine, N, -dimethylaniline.

In general, ammonia is then at least stoichiometric required amount of one mol up to 2 mol, preferably up to 1.2 mol Se mol 2-I) used chloromethyl phenyl isocyanate; to bind the in the cyclization Released hydrogen chloride is also at least the means to be used used in a stoichiometric amount of 2 moles per mole of 2-dichloromethylphenyl isocyanate, its amount can be up to 4, preferably up to 2.2 mol, also a larger excess is not harmful.

According to a second variant of the method according to the invention the 2-dichloromethyl-phenyl-isocyanates of the formula II in the first stage with at least 1 mol of ammonia converted to N- (2-dichloromethylphenyl) urea of the formula III and this after isolation in a second reaction step with elimination of Hydrogen chloride is cyclized to the 2-oxo-1,2-dihydroquinazoline of the formula I.

This is used in this variant of the process according to the invention 2-dichloromethyl-phenyl-isocyanate of the formula II, preferably in solvents, in which the N- (2-dichloromethylphenyl) urea of the formula III is sparingly soluble and precipitates from the reaction mixture, so that one undesirable in this case Cyclization reaction by splitting off hydrogen chloride with ammonia as hydrogen chloride binding agent cannot occur.

Examples of such solvents are: aliphatic Ethers such as diethyl ether, diisopropyl ether, aliphatic, cycloaliphatic and aromatic Hydrocarbons and halogenated hydrocarbons such as gasoline, ligroin, methylene chloride, Carbon tetrachloride, benzene, toluene, chlorobenzene, preferably methylene chloride and toluene.

In general, the reaction in this first stage will take place in the temperature range carried out between -20 and + 50 ° C, preferably between 0 and 30 ° C.

The stoichiometrically required amount of 1 mole of ammonia per mole 2-dichloromethyl-phenyl-isocyanate is generally suitable for quantitative conversion sufficient; however, an excess of ammonia up to 2 mol, in particular up to 1.2 moles can be used. A larger excess of ammonia is also mentioned above mentioned temperature range generally harmless.

Because of their poor solubility in those preferably used according to the invention Solvents can be the N- (2-dichloromethylphenyl) ureas of the formula III in generally in the usual way e.g.

isolated from the reaction mixture by filtration.

The second reaction step, the cyclization of the N- (2-dichloromethylphenyl) urea of the formula III with elimination of hydrogen chloride can be carried out in various ways be performed.

Once the ureas of the formula III can be used in a corresponding manner, as described above for the one-pot process, with solutions or suspensions Substances that bind hydrogen chloride such as ammonia, alkali and alkaline earth oxides and hydroxides and carbonates, heavy metal carbonates, tertiary amines in water and / or organic Solvents, as they have been mentioned above, are implemented. In general this reaction in the temperature range between 0 ° and 1000C, preferably between 200 and 800C.

The hydrogen chloride binding agent that is used is at least in a stoichiometric amount of 2 moles per mole of urea of the formula III used; an excess of up to 4 moles, in particular up to 2.2 moles, can be used even a higher excess is not harmful.

The urea of the formula III can also be used in an acidic aqueous medium cyclize.

Aqueous mineral acids such as hydrofluoric acid are preferably used, Hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid or organic Sulphonic acids such as benzene or p-toluene sulphonic acid, the concentration of the aqueous acid advantageously between 2 and 50 percent by weight, in particular between 10 and 25 percent by weight of pure acid in the aqueous solution. In general the cyclization reaction takes place in acidic aqueous solution even at temperatures below 60 ° C, but the temperature range between 60 and 1000C is preferred. Namely, it is advantageous to have the reaction in one - depending on the type and concentration the acid used - to carry out a sufficiently high reaction temperature 1 that the 2-oxo-1, 2-dihydro-quinazoline of the formula obtained as the cyclization product 1 goes into solution as the quinazolinium salt.

It is also possible to use alcohols or other water-miscible organic ones Add solvent to the reaction medium in order to achieve complete or partial solution to achieve the ureas of formula III; in general, however, this means no advantage.

The quinazolinium salts formed remain after the reaction has ended generally in solution; the corresponding quinazoline of formula I can be in usually by neutralizing the solution and e.g. isolate by filtration.

Furthermore, you can the compounds of formula I after a further Variant of the process according to the invention obtained in that the ureas of the formula III is reacted with excess alcohol.

The implementation according to the invention is explained using the example of N- (2-dichlorophenyl) urea by the following equation: An aliphatic alcohol having 1 to 4 carbon atoms is preferably used as the alcohol; as such, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol and tert-butanol may be mentioned.

-Generally in the temperature range between 50 0C and the boiling point of the alcohol used. Generally takes place in the course the reaction solution of the urea of the formula III used in the alcohol used from which the quinazolinium chloride of formula 1 later precipitates, then can one the compound of formula I after dissolving the chloride in water and then Isolate neutralization in the manner described above.

According to a further variant of the process according to the invention, the compounds of the formula I can also be obtained from the ureas of the formula III by heating to temperatures above about 130 ° C., as shown below by the formula scheme using the example of N- (2-dichloromethylphenyl) urea may be: Either the urea of the formula III can be heated gradually to 130 to 250.degree. C., preferably up to 0, to a temperature between 150 and 200.degree. C., in particular between 150 and 170.degree. However, it is also possible to heat a suspension of the urea of the formula III in an appropriately high-boiling solvent to the appropriate temperature, but preferably in the boiling solvent, until the elimination of hydrogen chloride has ended.

Common solvents can be used as solvents accordingly high boiling point use, preferably dichlorobenzene and tetralin or higher boiling naphtha fractions.

The quinazolinium chloride obtained as the reaction product is generally sparingly soluble and precipitates during the reaction; it can after the reaction has ended easily separated and isolated in the usual manner. The appropriate connection of the formula I can be obtained therefrom as described above in the customary manner and to be isolated.

It was surprising that the process of the invention was practical runs quantitatively without side reaction, since in the first step with simultaneous reaction of the dichloromethyl group with ammonia to form aminal -like Compounds and in the second stage with insufficient reactivity of the urea of the formula III had to be expected for the ring closure. The technical The progress of the method according to the invention results from the following advantages compared to the prior art: those used as starting compounds 2-Dichloromethyl-phenyl isocyanates of the formula II are easily accessible compounds.

Instead of the further starting compound required according to the prior art Urea is only required for the more easily accessible ammonia. For the cyclization reaction with elimination of hydrogen chloride is a binding agent for hydrogen chloride either not required or it can be readily available and inexpensive Compounds such as ammonia, alkali and alkaline earth hydroxides, oxides and carbonates be chosen, which in many cases as otherwise unusable by-products for To be available.

The process according to the invention generally gives short reaction times practically quantitative yields; for its implementation are at usual reaction temperatures no complex equipment necessary.

The 2-oxo-1,2-dihydro-quinazolines of the formula I are valuable intermediates e.g. for the production of pharmaceuticals and pesticides. E.g. leave them According to reports 29, 1313 (1896) with phosphorus-V-chloride into corresponding 2-chloroquinazolines convert which in turn are key products to produce a range called organic or represent pharmacologically effective described products. E.g. one obtains with ammonia or amine-like reaction components 2-amino-quinazoline with bactericidal or microbicidal properties (US-Ps 3 541 212; Japanese patent application 3 911/68; GB-PS 1,024,907; GB-PS 1 024 908), with pharmacological properties (B-PS 705 970) or with antioxidant properties (GB-PS 902 804).

Examples Preparation of 2-dichloromethyl-phenyl isocyanates Example 1 In 2885 g of o-tolyl isocyanate (boiling point 10: 70 °; nD20; 1.5360) at 110 to 125 ° C initiated under UV irradiation 3 kg of chlorine.

Then nitrogen is passed through at 120 ° C for 1 1/2 hours, in order to split the resulting carbamic acid chloride into isocyanate and hydrogen chloride. In the subsequent distillation, 1282 g of a forerun are obtained, in the following Approach can be used again and then at 127 ° C / 14 Torr 2302 g of 2-dichloromethylphenyl isocyanate; nD20: 1.5750; 98% purity (according to the chromatogram).

According to Example 1, by chlorination in the temperature range 120 to 150 ° C obtained: 3-chloro-2-dichloromethyl-phenyl isocyanate boiling point: 147 ° C / 12 Torr; Melting point: 45 ° C. 4-chloro-2-dichloromethyl-phenyl isocyanate, boiling point: 150 up to 151 ° C / 14 torr; Melting point: 71 ° C 5-chloro-2-dichloromethyl-phenyl isocyanate Boiling point: 150 ° C / 14 torr; nD20: 1,5892 6-chloro-2-dichloromethyl-phenyl isocyanate boiling point: 145 ° C / 12 torr; nD20: 1,5879 3,6-dichloro-2-dichloromethyl-phenyl isocyanate boiling point: 163 ° C / 11 torr; Melting point: 53 to 54 ° C. Production of N- (2-dichloromethylphenyl) urea of the formula III Example 2 In a solution of 20.2 g of 2-dichloromethyl-phenyl isocyanate Gaseous gas is passed into 100 ml of toluene at 15 ° to 200 ° C. with weak cooling Ammonia in excess. The separated solid product will vacuumed and dried. Yield: 21 g of N- (2-dichloromethylphenyl) urea (95.5 % of theory). Sinters from around 140 ° C without melting.

C8H8Cl2N20 (Mol 219.1) Elemental analysis: Calc .: 43.85% C, 3.68% H, 32.4% Cl, 12.8% N Found: 44.1 3.7 32.6 12.9 Example 3 In the solution of 236.5 g (iMol) 4-chloro-2-dichloromethylphenyl isocyanate in 1.2 l of toluene is passed in with cooling at 15 - 200C gaseous ammonia up to an excess. The deposited best product is sucked off and dried. 220 g (87% of theory) of N- (4-chloro-2-dichloromethylphenyl) urea are obtained, which sinters from around 150 ° C, but does not melt up to 2500C.

Example 4 Into the solution of 236.5 g (1 mol) of 5-chloro-2-dichloromethylphenyl isocyanate in 1.2 l of toluene is passed with cooling at 15 - to gaseous ammonia up to Excess one. The deposited solid product is filtered off with suction and dried. Man receives 215 g (91% of theory) of N- (5-chloro-2-dichloromethylphenyl) urea; sinters from about 150 ° C, does not melt up to 250 ° C.

Example 5 Into the solution of 236.5 g (1 mol) of 6-chloro-2-dichloromethylphenyl isocyanate in 1.2 l, while cooling at 15 ° -200 ° C., gaseous ammonia is passed in to excess a. The deposited solid product is filtered off with suction and dried. You get 215 G (85% of theory) N- (6-chloro-2-dichloromethylphenyl) urea; sinters from around 1500C, does not melt up to 250 ° C.

The following were obtained in a corresponding manner: N- (3-chloro-2-dichloromethyl) phenyl) urea Cl content: Calc .: 42.0 5 '; Found: 42.25 'N- (3,6-dichloro-2-dichloromethyl-phenyl) -urea Cl content: Calc .: 49.3 5 '; Found: 49.6 5 'Preparation of 2-oxo-1,2-dihydro-quinazolines a) One-pot process Example 6 20.2 g (0.1 mol) of 2-dichloromethyl phenyl isocyanate are concentrated in a mixture of 30 g with slight cooling at 15 to 200C aqueous ammonia solution and 100 ml of dioxane were added dropwise. After the heat of reaction has subsided the mixture is gradually heated to 7000 and stirred for a further 1 hour at this temperature. It is then cooled, the reaction product is filtered off with suction, washed with water and dried. 12 g (82.3% of theory) of 2-oxo-1,2-dihydro-quinazoline, which is up to 2500C does not melt.

C8H6N20 (Mol 146.15) Elemental Analysis: Calc .: 65.7% C, 4.14% H, 19.16 % N Gef .: 65.2 4.2 19.0 Cl content: <0.5% b) cyclization of the N- (2-dichloromethylphenyl) ureas Example 7 21.9 g (0.1 mol) of N- (2-dichloromethylphenyl) urea are suspended in 100 ml of ethanol. 20 g of concentrated aqueous ammonia are added and gradually heats up to boiling.

After 1 hour of boiling, the mixture is cooled and the solid product is filtered off with suction and dried. Yield: 13 g of 2-oxo-1,2-dihydroquinazoline (89% of theory); Melting point > 250 ° C.

Example 8 190 g (0.75 mol) of N- (4-chloro-2-dichloromethyl-phenyl) -urea are suspended in 1 l of ethanol. 100 ml are added dropwise to this at room temperature concentrated aqueous ammonia and then heats the mixture to the boil. After boiling for one hour, it is cooled to room temperature and weakly with acetic acid acidified. The solid product is filtered off and kneaded dry.

125 g (93% of theory) of 6-chloro-2-oxo-1,2-dihydroquinazoline are obtained; Melting point> 250 ° C.

Elemental analysis: Calc .: 53.25% C; 2.79%% H; 19.65 ffi Cl; 15.52 % N Found: 53.2 ffi a; 2.8 ffi H, # 19.5% Cl; 15.5% N Example 9 21.9 g (0.1 mol) N- (2-dichloromethylphenyl) urea are boiled in 150 ml of 10 pointer hydrochloric acid heated until a clear solution has formed. Allow to cool, give ammonia to pH 8 to 9 and let stand in ice for some time. Then the precipitate vacuumed and dried. Yield: 14.1 g of 2-oxo-1,2-dihydro-quinazoline (96% of Theory).

Example 10 21.9 g (0.1 mol) of 2-dichloromethyl-phenylurea become suspended in 120 ml of 95% ethanol and gradually heated to boiling. To If a clear solution occurs temporarily, a solid product separates out. Man boils for 1 hour and then sucks the hydrochloride of 2-oxo-1, 2-dihydroquinazoline away.

This is suspended in 100 ml of water and the aqueous suspension ammonia is added at 40 to 50 ° C until a pH of 8 to 9 is reached. After stirring for 1/2 hour at this temperature, it is filtered off with suction and dried. Yield: 14.0 g of 2-oxo-1,2-dihydro-quinazoline (95% of theory).

Example 11 190 g (0.75 mol) of N- (5-chloro-2-dichloromethyl-phenyl) -urea are gradually heated to boiling in 1 l of ethanol and reflux for 1 hour cooked. At around 500C a clear solution is created temporarily, from which immediately then the hydrochloride of 7-chloro-2-oxo-1,2-dihydro-quinazoline separates. This is suctioned off, suspended in 1 l of water at 40 - 50 ° C and then with concentrated aqueous ammonia added until the reaction is weakly alkaline. One stirs with this temperature until the pH value no longer changes (approx. 1 hour) and then weakly acidifies with acetic acid. The solid product is suctioned off, several times washed with water and dried at 10,000. 140 g (90% of theory) are obtained 7-chloro-2-oxo-1,2-dihydro-quinazoline; Melting point> 250 ° C.

Elemental analysis: Calc .: 53.25 46 C; 2.79 ffi H; 19.65% oil; 15.52 % N Found: 53.6% C; 2.6% H; 20.00% oil; 15.5% N Example 12 19.0 g (0.75 mol) of N- (6-chloro-2-dichloromethyl-phenyl) -urea are dissolved in 1 l of ethanol suspended. The mixture is gradually heated to the boil and refluxed for an hour. At around 500C a clear solution is created, which can also be used for prolonged cooking no solid product separates. About 700 ml of ethanol are distilled off and then left the remaining hot solution into a mixture of 100 ml concentrated aqueous Run in ammonia and 1 liter of water. The mixture is one hour at room temperature stirred, then neutralized with acetic acid. The solid product is suctioned off, several times washed with water and dried at 10,000. 112 g (83% of theory) are obtained 8 chlorine 2-oxo-1,2-dihydro-quinazoline; Melting point> 300 ° C.

Elemental Analysis: Calcd .: 53.25% C; 2.79% H; 19.65% Cl; 15.52% N Found: 52.8% C; 2.9 ffi H; 19.4% Cl; 15.2% N Example 13 21.9 g (0.1 mole) of N- (2-dichloromethylphenyl) urea are suspended in 150 ml of tetralin. The mixture is first to 150 ° C after If the evolution of hydrogen chloride subsided, the mixture was gradually heated up to 200 ° C. After no more hydrogen chloride escapes, the mixture is cooled and the hydrochloride suctioned off the 2-oxo-1,2-dihydro-quinazoline, washed with acetone or ether and dried.

The hydrochloride is converted into the free compound as described in Example 10 convicted. Yield: 14.0 g of 2-oxo-1,2-dihydroxyquinazoline (95% of theory).

The following were obtained in an analogous manner: 5-chloro-2-oxo-1,2-dihydro-quinazoline; Melting point:> 250 ° C Calc .: 53.25% C Found: 53.0% C 2.79% H 2.9% H 19.65% Cl 19.4% Cl 15.52% N 15.3% N 5.8- Dichloro-2-oxo-1,2-dihydro-quinazoline; Melting point:> 2500C Calc .: 44.6% CC Found: 43.8% C 1.87 H 2.0% H 32.95% Cl 32.7% Cl 13.03% N 12.85% N All these compounds show im Infrared spectrum a characteristic carbonyl band at 1680 cm 1.

Claims (8)

Patent claims: 1. Process for the preparation of 2-oxo-1,2-dihydro-quinazolines of the formula in which X is halogen and n is one of the numbers 0, 1, 2, 3 and 4, characterized in that 2-dichloromethylphenyl isocyanates of the formula in which X and n have the meaning given above, are reacted with ammonia and the reaction product formed is cyclized, optionally without intermediate isolation, with elimination of hydrogen chloride. 2) Method according to claim 1, characterized in that the Reaction with at least 3 moles of ammonia per mole of 2-dichloromethylphenyl isocyanate without Performs intermediate insulation. 3) Process according to claims 1 and 2, characterized in that instead of 2 moles of ammonia, the corresponding amount of another hydrogen chloride is used binding agent used. 4) Process according to claim 1, characterized in that the resulting as reaction product N- (2-dichloromethylphenyl) urea of the formula in which X is halogen and n is one of the numbers 0, 1, 2, 3 and 4, cyclized with elimination of hydrogen chloride. 5) Process according to claims 1 and 4, characterized in that cyclized with the aid of an agent which binds hydrogen chloride. 6) Process according to Claims 1 and 4, characterized in that cyclized in the presence of aqueous mineral acid. 7) Process according to claims 1 and 4, characterized in that cyclized by reaction with an alcohol. 8) Process according to claims 1 and 4, characterized in that cyclized by heating to a temperature above 1300C.