2-(arylimino-methyl)-3-dialkylaminoacrylonitriles, a process for their preparation and their use
The invention relates to 2-(arylimino-methyl)-3dialkylamino-acrylonitriles, a process for their preparation by reaction of β-anilinoacrylonitriles with orthoformic acid amides and their use for the preparation of 4-amino-5-iminiummethylene-2-pyrimidines or 4-amino-5-formly-2-pyrimidines. 
     As cyanomalonodialdehyde derivatives, 2-(arylimino-methyl)-3-dialkylamino-acrylonitriles are important components for the preparation of various heterocyclic compounds. It is thus possible to obtain from these intermediate products, for example, formyl- and cyanopyrimidines (JP 84-201 804 and JP 84-152 096), cyanopyrazoles (Mh. Chem. 124(1993), 199) and cyanopyridines (Synthesis 1987, 1124). 4-Amino-5-formyl-2-methylpyrimidine, which is an industrially important precursor of 4-amino-5-aminomethyl-2-methylpyrimidine (&#34;Grewe-diamine&#34;, intermediate prodcut for the preparation of vitamin B1), is particularly important. 
     The invention thus relates to a process for the preparation of compounds of the formula ##STR1## wherein R 1  and R 2  independently of one another denote linear or branched C 1  -C 8  -alkyl, C 2  -C 8  -alkenyl, C 2  -C 8  -alkoxyalkyl, C 3  -C 8  -alkoxyalkenyl, C 3  -C 8  -cycloalkyl, C 7  -C 10  -aralkyl, C 6  -C 12  -aryl or heterocyclic ring having 1 or 2 heteroatoms from the series consisting of N, O and S, or 
     R 1  and R 2 , together with the nitrogen atom on which they are located, denote a 5- to 8-membered ring which can contain a further heteroatom from the series consisting of N, O and S and 
     R 3  to R 7  independently of one another denote linear or branched C 1  -C 8  -alkyl, C 1  -C 6  -alkoxy, C 1  -C 6  -alkylthio, C 2  -C 8  -alkenyl, C 2  -C 8  -alkoxyalkyl, C 3  -C 8  -cycloalkyl, halogen, di-C 1  -C 6  -alkylamino or, preferably, hydrogen, 
     by reaction of compounds of the formula ##STR2## wherein R 3  to R 7  have the above meaning, 
     with compounds of the formula ##STR3## wherein R 1  and R 2  have the above meaning and 
     A and B independently of one another denote OR 8 , OR 9 , NR 10  R 11  or NR 12  R 13 , wherein the substituents R 8  to R 13  independently of one another have the meaning defined above for R 1  and R 2 , 
     in a molar ratio of II/III of 0.5 to 20, preferably 0.8 to 5, in particular 1 to 3, at a temperature of 0° to 200° C., preferably 20° to 150° C. 
     The presure depends on the reaction temperature and on the nature of the compound III, in particular on the boiling point of the products HA and HB, and can be 0.1 to 20, preferably 1 to 5 bar. 
     The accessibility of the compound I by the process according to the invention is extremely surprising. In fact, reaction products of aniline and acetaldehyde exist not in the form 1 but in the form 2 ##STR4## 
     (M. Jachak et al., Monatshefte fur Chemie 124, 199 (1993) in association with H.-J. Sturm et al., Liebigs Ann. Chem. 729, 139 (1969)). Accordingly, it would have to have been expected that alkylation o the nitrogen should take place during the reaction with compound III;, R. F. Abdulla et al., Tetrahedron 35, 1675 et seq. (1979). 
     Linear and branched C 1  -C 8  -alkyl includes, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl and one of the isomeric pentyls, hexyls or octyls, preferably the C 1  -C 4  -alkyl radicals mentioned. 
     Linear or branched C 2  -C 8  -alkenyl includes, for example, vinyl, propenyl, allyl or one of the isomeric butenyls, pentenyls, hexenyls or octenyls, preferably the C 3  -C 4  -alkenyl radicals mentioned. 
     Linear or branched C 2  -C 8  -alkoxyallkyl includes, for example, methoxymethyl, ethoxymethyl and other radicals from the group consisting of C 3  -C 9  -alkyl in whch a CH 2  group is replaced by an O atom. 
     Linear or branched C 3  -C 8  -alkoxyalkenyl includes, for example, methoxyvinyl, ethoxyvinyl, methoxyallyl, 2-methoxy-propenyl and other radicals from the group consisting of C 4  -C 9  -alkenyl wherein a CH 2  group is replaced by an O atom. 
     C 3  -C 8  -acycloalkyl includes, for example, cyclopropyl, methylcyclopropyl, dimethylcyclopropyl, cyclobutyl, methylcyclobutyl, cyclopentyl, methylcyclopentyl, cyclohexyl, methyl-cyclohexyl, dimethyl-cyclohexyl, cycloheptyl and cyclooctyl, preferably cyclopropyl and cyclohexyl, and methyl and dimethyl derivatives thereof. 
     C 7  -C 10  -Aralkyl includes, for example, 1-phenylethyl, 2-phenylethyl and preferably benzyl. 
     5- to 8-Membered saturated or unsaturated heterocyclic rings having 1 to 2 heteroatoms from the group consisting of N, O and S which may be mentioned are: pyrrole, furan, thiophene, pyrrolidine, pyrroline, pyrazole, imidazole, thiazole, oxazole, pyridine, pyrimidine, piperazine, morpholine, pyran, azepine, azocine, isoxazole, isoxazole, isothiazole, pyridazine and pyrazine, which can be substituted on the N atom by C 1  -C 4  -alkyl or by hydroxy-C 1  -C 4  -alkyl. The heterocyclic rings morpholine, pyrrolidine and piperidine, which can be substituted by C 1  -C 4  -alkyl or by hydroxy-C 1  -C 4  -alkyl, are particularly preferred. 
     R 1  and R 2  independently of one another preferably denote linear or branched C 1  -C 8  -alkyl, cyclopropyl, cyclopently, cyclohexyl, phenyl or benzyl or, together with the nitrogen atom on which they are located, a 5- or 6-membered ring which can contain a further heteroatom from the series consisting of N, O and S. 
     R 1  and R 2  independently of one another particularly denote linear or branched C 1  -C 4  -alkyl or, together with the nitrogen atom on which they are located, morpholine, pyrrolidine or piperidine, which can be substituted by C 1  -C 4  -alkyl or hydroxy-C 1  -C 4  -alkyl. 
     The starting materials II, such as, for example, 3-phenylaminoacrylonitrile, can be prepared, for example, from aniline, 3-ethoxyacrylonitrile and ammonia in accordance with EP-A 18 473 or in an analogous manner. 
     Dialkylaminoacrylonitriles, which are easily accessible industrially in a virtually quantitative yield, for example analogously to EP-A-560 158, can arylamines with the addition of acid to give the starting materials II. 
     The starting materials III include dimethylformamide acetals, aminal esters and triaminomethanes of the formulae ##STR5## 
     The reactions according to the invention can be illustrated by way of example as follows: ##STR6## 
     The process according to the invention can be carried out in the presence or absence of an organic solvent. Preferred organic solvents are aprotic and polar solvents, for example N-persubstituted acid amides, such as dimethylformamide (DMF), dimethylacetamide (DMAC), diethylacetamide and homologues thereof, N-methyl-pyrrolidone (NMP), N-methyl-caprolactam (NMC), phosphoric acid hexamethyl-triamide, tetramethyl-urea and the like, the group consisting of sulpholane and its derivatives substituted by methyl, ethyl and other inert substituents, the group consisting of sulphoxides, such as dimethyl sulphoxide, diethyl sulphoxide and others, and the group consisting of sulphones, such as diethyl sulphone, dimethyl sulphone and others. Since o-amides also have a polar aprotic character, it is possible to employ an excess of the compounds III as solvents and diluents endogenous to the system. It is even possible to dispense entirely with aprotic polar solvents which are foreign to the system. In the case where a foreign solvent is employed, N-persubstituted acid amides, specifically NMP, NMC, DMF or tetramethyl-urea, are especially preferred. 
     The progress of the reaction can be monitored, for example, by thin layer chromatography. When the reaction has ended, the solvent (if present) and the (usually) readily volatile alcohols and amines HA and HB can be stripped off. Since the reaction proceeds very selectively, the crude product often already has a purity of more than 95% and can thus, for example, be used directly for synthesis of heterocyclic compounds. 
     The invention also relates to the compounds I and their use for the preparation of 4-amino-5iminiummethylene-2-pyrimidines or 4-amino-5-formly-2-pyrimidines. For this purpose, the compounds I can be reacted with C 1  -C 6  -amidines at elevated temperature, for example at 60° to 150° C., to give the 4-amino-5-iminiummethylene-2-pyrimidines, from which the corresponding 5-formyl compounds are formed by hydrolysis in the case of aqueous working up. 
     The percentage data of the following examples in each case relate to the weight. 
    
    
     EXAMPLES 
     Example 1 
     29 g of trans-3-ethoxyacrylonitrile, 20.5 g of ammonia, 21 g of aniline and 10 ml of ethanol were stirred in a 0.31 V4A autoclave at 1000° C. for 4 hurs. After the ethanol had been distilled off, 200 ml of water were added and the mixture was extracted 3 times with 100 ml of diethyl ether. The 33 g of residue obtained after concentration were recrystallized from chloroform, which gave 15.2 g of trans-3-phenylaminoacrylonitrile. The product was identified by GC/MS analysis and comparison of the NMR data with that from EP-A 18 473. 
       1  H NMR (d-DMSO): 4.60 ppm (d,1H); 6.9-7.3 (m,5H); 7.85 (dd, 1H); 9.70 (d,1H) 
     Example 2 
     405 g of acetonitrile and 913 g of 89.6% pure ethoxy-bis(dimethylamino)methane (remainder DMF) were heated in a 31 V4A steel autoclave at 140° C. for 12 hours. After distillation, 3-dimethylaminoacrylonitrile was obtained as 98.8% pure product yield of 96.7% of theroy. 
     29 g of 3-dimethylaminoacrylonitrile, 28 g of aniline and 20 g of glacial acetic acid were stirred in 100 ml of dichloroethane at room temperature for 17 hours. 
     Water was then added in a volume ratio of 1:1, the phases were separated and the aqueous phase was extracted with dichloroethane. After the combined organic media had been concentrated, 40 g of crude product were obtained, which slowly crystallized completely. 
     According to  1  H NMR, 90% of trans-3-phenylaminoacrylonitrile, 5% of the cis compound and 3% of dimethylaminomethyleneglutaconic acid dinitrile were present 
       1  H NMR of the cis compound (d-DMSO): 4.27 ppm (d, 1H); 7.50 (dd, 1H); 6.9-7.3 (m, 5H), 9.52 ppm (d, 1H) 
     Example 3 
     14.4 g of trans-3-phenylaminoacrylonitrile, 20 ml of 82% pure DMF dimethyl acetal (contained DMF and methanol) and 150 ml of DMF where boiled under reflux for 2 hours. After the mixture had been concentrated on a rotary evaporator, 20.0 g of 97.8% pure 3-phenylimino-2-dimethylaminopropene-2-nitrile were obtained, corresponding to 98.3% of theory. 
       1  H NMR (d-DMSO: 3.18 and 3.31 ppm (broad s, each 3H, NMe 2 ); 6.95-7.10 and 7.25-7.35 (m, 5H, phenyl), 7.60 (s, 1H).