Abstract:
A novel process for producing α-[(dialkylamino) substituted-methylene]β-oxo-(substituted) propanenitriles of the formula: ##STR1## where R, R 1  and R  2  are defined in the specification by reacting a substituted isoxazole with a diaklylamide dimethylacetal is provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a process for the synthesis of α-[(dialkylamino)substituted methylene]-β-oxo-(substituted)propanenitrile compounds and to novel substituted isoxazole compounds useful as intermediates in the process. 
     2. Description of the Prior Art 
     The α-[(dialkylamino)substituted-methylene]-β-oxo-(substituted)propanitrile compounds are important intermediates for the preparation of therapeutic aryl and heteroaryl [7-(aryl and heteroaryl)pyrazolo(l,5-a)-pyrimidin-3-yl]methanone compounds which are useful as anxiolylic, antiepileptic, sedative-hypnotic and skeletal muscle relaxant agents. The aryl and heteroaryl [7-(aryl and hetroaryl)-pyrazolo [1,5-a] pyrimidin-3-yl]methanone compounds and uses for such compounds are described in U.S. Pat. No. 4,521,422, the contents of which are incorporated by reference. 
     In U.S. Pat. No. 4,900,836, the contents of which are incorporated by reference, a series of reactions in which the α-[(dialkylamino)substituted methylene]-β-oxo-(substituted)propanenitrile compounds are utilized to produce the [7-(alkyl and hetroaryl)pyrazolo (1,5-a)-pyrimidin-3-yl]methanone compounds is described. This reference also describes the synthesis of the α-[(dialkylamino) substituted methylene]-β-oxo-(substituted) propanenitrile compounds via the reaction of a substituted acetonitrile with a dimethylformamide dimethylacetal. 
     It has now been found that α-[(dialkylamino) substituted methylene]β-oxo-(substituted) propane nitrile compounds may be advantageously synthesized via reaction of a substituted isoxazole with a dialkylamide dimethylacetal. The use of substituted isoxazole compounds in the production of α-[(dialkylamino)substituted methylene]-β-oxo(substituted)propanenitrile compounds has not been taught nor suggested by the art. 
     Certain substituted isoxazole compounds and their synthesis are known. For example, 5-(2,3,4,5-tetrafluorophenyl)-isoxazole (Chem. Abst. Registry No. 110985-65-4), 5-(2,4-dichloro-5-fluorophenyl) isoxazole (Registry No. 103318-74-6), 5-(2,3,-dichloro-phenyl) isoxazole (Registry No. 76344-98-4), 5-(5-nitro-2-furyl)-isoxazole (Registry No. 32332-91-5), 5-(4-methylphenyl)-isoxazole (Registry No. 7064-35-9), 5-(m-chloro phenyl) isoxazole (Registry No. 7064-34-8), 5-(m-bromo phenyl) isoxazole (Registry No. 7064-33-7), 5-(p-chloro-phenyl) isoxazole (Registry No. 7064-32-6), 5-(p-bromo phenyl) isoxazole (Registry No. 7064-31-5), N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-2-5-isoxazolyl)-3-thiophenesulfonamide (Registry No. 103118-33-8), 3-hydroxy-4-(5-isoxazolyl)-2(5H)-foranone (Registry No. 84-608-81-1) and 5-phenyl isoxazole (Registry No. 1006 -67-3) are known. Other substituted isoxazole compounds including those claimed herein are not known. 
     SUMMARY OF THE INVENTION 
     The invention provides an improved process for the large scale production of α-[(dialkylamino)substituted-methylene]-β-oxo-(substituted)propanitrile compounds which may be represented by the following structural formula: ##STR2## wherein R is lower alkyl(C 1  -C 3 ); R 1  is selected from the group consisting of phenyl; phenyl substituted by one of the group selected from halogen, nitro, alkyl(C 1  -C 3 ) and alkoxy(C 1  -C 3 ); phenyl di- or trisubstituted by methoxy, halogen and lower alkyl; phenyl substituted by one of the group consisting of dialkylamino(C 1  -C 3 ), methylenedioxy, alkylthio(C 1  -C 3 ), alkylsulfonyl(C 1  -C 3 ), amino, alkanoyl(C 1  -C 3 ), amino, trifluoromethyl and phenyl; thienyl; thienyl substituted by one or two of the group selected from halogen and alkyl(C 1  -C 3 ); furanyl; furanyl substituted by one or two of the group selected from alkyl(C 1  -C 3 ), naphthalenyl, pyrazinyl, and pyrrolyl; and R 2  is selected from the group consisting of hydrogen and lower alkyl (C 1  -C 3 ). The improved process comprises reacting an R 1  substituted isoxazole having the formula ##STR3## wherein R 1  is as defined above with a dialkylamide dimethylacetal having the formula ##STR4## wherein R and R 2  are as defined above at a temperature from about 50° C. to about 100° C. and recovering the α-[(dialkylamino)substituted methylene]-β-oxo-(substituted) propanenitrile so produced. The invention also provides certain novel R 1  substituted isoxazole compounds. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The process and compounds of the present invention are described in the following reaction scheme I: ##STR5## 
     In accordance with the above reaction scheme a 1-(cyclicsubstituted)ethanone (1), where R 1  is as described above, is reacted with dimethylformamide dimethyl acetal (2) for 15 hours at 50°-100° C. Evaporation and recrystallization gives the 3-dimethylamino-1-(substituted)-2-propen-1-one (3). 
     The 3-dimethylamino-1-(substituted)-2-propen-1-one compounds (3) and their synthesis are described in greater detail in U.S. Pat. No. 4,178,449 (col 2 lines 44-54), U.S. Pat. No. 4,281,000 (col 2 lines 28-34), and U.S. Pat. No. 4,236,005 (col 2 lines 45-54). 
     The 3-dimethylamino-1-(substituted)-2-propen-1-one (3) is reacted with hydroxylamine hydrochloride in absolute methanol for 2 hours at a temperature from about 50° to about 100° C. The reaction solution is evaporated, dissolved in methylene chloride and passed thru hydrous magnesium silicate. Concentration of the eluate gives the desired substituted isoxazole (5) which is reacted with a dialkylamide dimethylacetal (6) at a temperature from about 50° to about 100° C. for 4 hours. The reaction solution is evaporated, dissolved in methylene chloride and passed thru hydrous magnesium silicate. On cooling and/or concentrating the methylene chloride solution, the desired α-[(dialkylamino)substituted methylene]-β-oxo-(substituted) propanenitrile (7) crystallizes. 
     As described in U.S. Pat. No. 4,900,836, the α[(dialkylamino)substituted methylene]-β-oxo-(substituted)propanenitriles find utility as intermediates in the preparation of therapeutic aryl and heteroaryl[7-(aryl and heteroaryl)pyrazolo(1,5-a)pyrimidin-3-yl] methanones. As described in U.S. Pat. No. 4,521,422 the aryl and heteroaryl [7-(aryl and heteroaryl)pyrazolo(l,5-a) pyrimidin-3-yl]methanones are useful as anxiolylic, antiepileptic, sedative-hypnotic, and skeletal muscle relaxant agents. 
     The above described process is an improvement over the procedure described in U.S. Pat. No. 4,900,836. The 1-(cyclicsubstituted)ethanones are readily available and inexpensive; the over all yields are higher; and the reaction work-ups are less labor and time intensive. 
     The following non-limiting examples illustrate the process of the present invention as well as the preparation of the novel compounds isoxazole intermediates. 
     EXAMPLE 1 
     3-Dimethylamino-1-(3-thienyl)-2-propen-1-one 
     A mixture of 48.4 g of 3-acetylthiophene and 75 ml of dimethylformamide dimethyl acetal, under nitrogen, is heated for 15 hours on a steam bath. The reaction is concentrated in vacuo and the residue crystallized from methylene chloride/hexane to give 60.55 g (87%) of the desired product, mp 89°-90° C. 
     Using the general procedure of Example 1, the following compounds of Example 2-26 shown in Table 1 are prepared. 
     
                                           TABLE I__________________________________________________________________________ExampleStarting Material              Compound             MP °C.__________________________________________________________________________ 2   Acetophenone  3-dimethylaminoacrylophenone                                   93.0-94° 3   2-Acetyl-5-bromothiophene              1-(5-bromo-2-thienyl)-3-dimethylamino-2-                                   118-120°              propen-1-one 4   4&#39;-Chloroacetophenone              trans-4&#39;-chloro-3-dimethylaminoacrylo-                                   83-84°              phenone 5   4&#39;-Methoxyacetophenone              3-dimethylamino-4&#39;-methoxyacrylophenone                                   92-95° 6   4&#39;-Methylacetophenone              3-dimethylamino-4&#39;-methylacrylophenone                                   92.5-95° 7   2-Acety-5-methylthiopene              1-(5-methyl-2-thienyl)-3-dimethylamino-2-                                   113-115°              propen-1-one 8   2-Acetylfuran 3-(dimethylamino)-1-(2-furyl)-2-propen-                                   84-86°              1-one 9   2-Acetyl-5-methylfuran              3-(dimethylamino)-1-(5-methyl-2-furanyl)-                                   126-128°              2-propen-1-one10   3&#39;-Ethylacetophenone              3-(dimethylamino)-1-(3-ethylphenyl)-2-                                   yellow orange              propen-1-one         viscous liquid11   4&#39;-Nitroacetophenone              3-dimethylamino-4&#39;-nitroacrylophenone                                   150-151°12   2&#39;-Fluoroacetophenone              ( .sub.-- E)-3-dimethylamino-2&#39;-fluoroacrylophenone                                   yellow oil13   4&#39;-Fluoroacetophenone              trans-3-dimethylamino-4&#39;-fluoroacrylo-                                   96-97°              phenone14   1-Adamanyl methyl ketone              3-dimethylamino-1-tricyclo[3.3.1.1.sup.3,7 ]-                                   142-143°              dec-1-yl-2-propen-1-one15   4&#39;-Acetylbiphenyl              3-dimethylamino-4&#39;-phenylacrylophenone                                     135-137.5°16   2&#39;-Acetonaphthone              ( .sub.-- E)-3-dimethylamino-2&#39;-acrylonaphthone                                   96-98°17   3&#39;,4&#39;-Dichloroacetophenone              trans-3&#39;,4&#39;-dichloro-3-dimethylamino-                                   94-95°              acrylophenone18   3&#39;,4&#39;-Dimethylacetophenone              3-dimethylamino-3&#39; ,4&#39;-dimethylacrylo-                                   108-110°              phenone19   2&#39;,4&#39;-Dichloroacetophenone              2&#39;,4&#39;-Dichloro-3-dimethylaminoacrylo-                                   83.5-85°              phenone20   2&#39;,6&#39;-Difluoroacetophenone              1&#39;-(2&#39;,6&#39;-difluorophenyl)-3-(dimethyl-                                   67-69°              amino)-2-propen-1-one21   2-Acetyl-4-methylthiophene              3-(dimethylamino)-1-(4-methyl-2-thienyl)-                                   102-104°              2-propen-1-one22   3-Acetyl-1-methylpyrrole              3-(dimethylamino)-1-(1-methyl-1H-pyrrol-                                   123-125°              3-yl)-2-propen-1-one23   2-Acetylthiophene              3-dimethylamino-1-(2-thienyl)-2-propen-1-                                   114-115°              one24   2-Acetyl-3-methylthiophene              ( .sub.-- E)-3-dimethylamino-1-(3-methyl-2-                                   45-49°              thienyl)-2-propen-1-one25   2&#39;,4&#39;-Difluoroacetophenone              3-dimethylamino-2&#39;,4&#39;-difluoroacrylo-                                   48-49°              phenone26   2&#39;,5&#39;-Difluoroacetophenone              3-dimethylamino-2&#39;,5&#39;-difluoroacrylophenone                                   66-67°__________________________________________________________________________ 
    
     EXAMPLE 27 
     A mixture of 58.1 g of (3-dimethylamino-1-(3-thienyl)-2-propen-1-one, 23.4 g of hydroxylamine hydrochloride and 250 ml of commercial absolute methanol is heated on a steam bath for 2 hours. The reaction is concentrated in vacuo, partitioned between methylene chloride and water and the organic layer dried over sodium sulfate. The methylene chloride is passed thru a short column of hydrous magnesium silicate and concentrated in vacuo to give 41.25 g (85%) of the desired product as a red-orange oil which solidified on standing. CI-MS: M/z 151(M + ). 
     Using the general procedure of Example 27, the following compounds of Example 28-52, shown in Table II are prepared. 
     
                       TABLE II______________________________________  Starting  MaterialExample  of Example            Compound        MP °C.______________________________________28      2        5-Phenylisoxazole                            Colorless liquid29      3        5-(5-Bromo-2-thienyl)-                            66-68°            isoxazole30      4        5-( -p-Chlorophenyl)-                            84-85°            isoxazole31      5        5-( -p-Methoxyphenyl)-                            64-65°            isoxazole32      6        5- -p-Tolylisoxazole                            60-61°33      7        5-(5-Methyl-2-thienyl)-                            30-32°            isoxazole34      8        5-(2-Furanyl)isoxazole                            Pale yellow oil35      9        5-(5-Methyl-2-furanyl)-                            32-33°            isoxazole36     10        5-(3-Ethylphenyl)isoxa-                            Colorless liquid            zole37     11        5-(4-Nitrophenyl)isoxa-                            172-174°            zole38     12        5-(2-Fluorophenyl)isoxa-                            Yellow liquid            zole39     13        5-(4-Fluorophenyl)isoxa-                            52-53°            zole40     14        5-Tricyclo[3.3.1.1..sup.3,7 ]-                            32-33°            dec-1-yl-isoxazole41     15        5-[1,1&#39;-Biphenyl]-4-yl-                            130-132°            isoxazole42     16        5-(2-Naphthalenyl)isoxa-                            110-112°            zole43     17        5-(3,4-Dichlorophenyl)-                            88-89°            isoxazole44     18        5-(3,4-Dimethylphenyl)-                            46-47°            isoxazole45     19        5-(2,4-Dichlorophenyl)-                            127-129°            isoxazole46     20        5-(2,6-Difluorophenyl)-                            63-64°            isoxazole47     21        5-(4-Methyl-2-thienyl)-                            pale yellow            isoxazole       liquid48     22        5-(1-Methyl-1 .sub.-- H-pyrrol-2-                            pale yellow            yl)isoxazole    liquid49     23        5-(2-Thienyl)isoxazole                            dark yellow-                            orange liquid50     24        5-(3-Methyl-2-thienyl)-                            pale yellow            isoxazole       liquid51     25        5-(2,4-Difluorophenyl)-                            64-66°            isoxazole52     26        5-(2,5-Difluorophenyl)-                            74-77°            isoxazole______________________________________ 
    
     EXAMPLE 53 
     α-[(Dimethylamino)methylene]-β-oxo-3-thiophenepropanenitrile 
     A mixture of 41.2 g of 5-(3-thienyl)isoxazole and 36.0 g of dimethylformamide dimethylacetal, under nitrogen, is heated on a stream bath for 4 hours. The reaction is concentrated in vacuo to give a viscous oil which solidified. The residue is dissolved in methylene chloride and passed thru a short column of hydrous magnesium silicate. On cooling, 31.76 g of the desired product is obtained, mp 118°-119°, CI-MS:m/z 206(M 30 ). Concentrating in vacuo the methylene chloride gives an additional 20.2 g of product. (Total recovered 51.96 g, 92%). 
     Using the general procedure of Example 53, the following compounds of Example 54-78, shown in Table III are prepared. 
     
                       TABLE III______________________________________  Starting  MaterialExample  of Example            Compound         MP °C.______________________________________54     28        2-Benzoyl-3-dimethyl-                             111-113°            aminoacrylonitrile55     28        5-Bromo-α-[(dimethyl-                             190-192°            amino)methylene]-β-oxo-2-            thiophenepropanenitrile56     29        2- -p-Chlorobenzoyl-3-                             118-121°            dimethylaminoacrylo-            nitrile57     30        α-[(Dimethylamino)methy-                             107-110°            lene]-4-methoxy-β-oxo-                             (dec)            benzenepropanenitrile58     31        α-[(Dimethylamino)methy-                             132-135°            lene]-4-methyl-β-oxo-            benzenepropanenitrile59     32        α-[(Dimethylamino)-                             151-153°            methyllene]-5-methyl-β-            oxo-2-thiophenepropane-            nitrile60     33        α-[(Dimethylamino)methy-                             112-115°            lene]-β-oxo-2-furanpro-            panenitrile61     34        α-[(Dimethylamino)-                             135-137°            methyllene]-5-methyl-β-            oxo-2-furanpropane-            nitrile62     35        α-[(Dimethylamino)-                             red-orange            methylene]-3-ethyl-β-oxo-                             oil            benzenepropanenitrile63     36        α-[(Dimethylamino)methy-                             154-156°            lene]-4-nitro-β-oxo-            benzenepropanenitrile64     37        α-[(Dimethylamino)methy-                             62-74°            lene]-2-fluoro-β-oxo-            benzenepropanenitrile65     38        α-[(Dimethylamino)methy-                             142-145°            lene]-4-fluoro-β-oxo-            benzenepropanenitrile66     39        α-[(Dimethylamino)methy-                             183-189°            lene]-β-oxo-tricyclo-            [3.3.1.1..sup.3,7 ]decane-1-            propanenitrile67     40        α-[(Dimethylamino)methy-                             174-176°            lene]-β-oxo-4-biphenyl-            propionitrile68     41        α-[(Dimethylamino)methy-                             115-118°            lene]-β-oxo-2-naphthalene-            propanenitrile69     42        3,4-Dichloro-α-[(dimethyl-                             130-142°            amino)methylene]-β-oxo-            benzenepropanenitrile70     43        α-[(Dimethylamino)methy-                              82-112°            lene]-3,4-dimethyl-β-oxo-            benzenepropanenitrile71     44        2,4-Dichloro-α-[(dimethyl-                             yellow glass            amino)methylene]-β-oxo-            benzenepropanenitrile72     45        α-[(Dimethylamino)methy-                             109-111°            lene]-2,6-difluoro-β-oxo-            benzenepropanenitrile73     46        α-[(Dimethylamino)methy-                             127-132°            lene]-4-methyl-β-oxo-2-            thiophenepropanetrile74     47        α-[(Dimethylamino)methy-                              97-100°            lene]-1-methyl-β-oxo-1 .sub.-- H-            pyrrole-2-propanenitrile75     48        α-[(Dimethylamino)methy-                             136-140°            lene]-β-oxo-2-thiophene-            propanenitrile76     49        α-[(Dimethylamino)methy-                             red-brown            lene]-3-methyl-β-oxo-2-                             viscous syrup            thiophenepropanenitrile77     50        α-[(Dimethylamino)methy-                             137-139°            lene]-2,4-difluoro-β-oxo-            benzenepropanenitrile78     51        α-[(Dimethylamino)methy-                             108-110°            lene]-2,5-difluoro-β-oxo-            benzenepropanenitrile______________________________________