Abstract:
The novel compound, 3-(o-aminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one and novel 3-(substituted aminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-ones, such as 3-(o-methylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one and 3-(o-benzylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one; useful as immunomodulators; and processes for the synthesis of the compounds.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention pertains to derivatives of 3,4-dihydrophthalazin-1(2H)-one in which that molecule has been substituted in the 3-position with either aminobenzoyl or a substituted aminobenzoyl. 
     (2) Description of the Prior Art 
     U.S. Pat. No. 3,882,119 discloses certain derivatives of 3,4-dihydrophthalazin-1(2H)-one and procedures for their synthesis. The disclosed derivatives consist of 3,4-dihydrophthalazin-1(2H)-one substituted in the 3-position with an aminobenzoyl halide (which may itself be substituted) in which the amino group is either para or meta and the halogen is ortho. 
     In Chemical Abstracts, vol. 72, No. 55483b, and Chemical Abstracts vol. 71, No. 124,361d, the compound, 3-(p-chlorobenzoyl)-3,4-dihydro-1(2H)-phthalazinone, and methods for its synthesis are disclosed. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention relates to novel compounds of the formula ##STR1## wherein 
     R 1  is H, C 1  -C 4  lower alkyl, C 3  -C 7  cycloalkyl, C 6  -C 14  aryl, C 6  -C 14  substituted aryl, or C 4  -C 13  heteroaryl, and 
     R 2  is H, C 1  -C 4  lower alkyl, C 1  -C 8  alkoxy, OH, NH 2  or NO 2 . 
     The invention also relates to a process which comprises reacting 3,4-dihydrophthalazin-1(2H)-one with a compound of the formula ##STR2## wherein R 1  and R 2  are defined as above to form a compound of the formula ##STR3## 
     DETAILED DESCRIPTION 
     Utility 
     The compounds of this invention are useful as immunomodulators. Immunomodulatory activity has been demonstrated for 3-(o-methylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, 3-(o-benzylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, and 3-(o-aminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one. 
     Compounds 
     The compounds of this invention are: ##STR4## wherein 
     R 1  is H, C 1  -C 4  lower alkyl (i.e., lower alkyl group of having one to four carbon atoms), C 3  -C 7  cycloalkyl, C 6  -C 14  aryl, C 6  -C 14  substituted aryl (including benzyl), or C 4  -C 13  heteroaryl, and 
     R 2  is H, C 1  -C 4  lower alkyl, C 1  -C 8  alkoxy, OH, NH 2  or NO 2 . 
     Formation of the Compounds 
     (1) Formation of 3-(Substituted aminobenzoyl)-3,4-dihydrophthalazin-1(2H)-ones 
     The reaction may be summarized as follows: ##STR5## where R 1  and R 2  are defined as above. 
     The above reaction is typically accomplished by reacting an N-substituted isatoic anhydride (compound I; prepared from isatoic anhydride by procedures described in G. E. Hardtmann et al, J. of Heterocyclic Chemistry, Vol. 12, p 565-572 (1975)) with an equivalent amount of 3,4-dihydrophthalazin-1(2H)-one (compound II) in an aprotic solvent such as toluene or xylene at elevated temperatures, preferably in the range from 100° C. to 145° C. The above reaction can also be performed in a polar solvent, such as dimethyl formamide, in which case a range of 70° C. to 90° C. is preferred. Depending on the solvent and the nature of compounds I and II, the time of the reaction is varied from 4 to 24 hours. The preferred reaction time is 16 hours. The product, 3-(substituted aminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one (compound III), forms a precipitate when the mixture is cooled to room temperature. The preceipitate may be washed with the aprotic solvent at room temperature. 
     (2) Formation of 3-(aminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one 
     Two grams of the catalyst, 10% Pd/C, is added to a suspension of 7.2 g of 3-(o-benzoylaminobenzyl)-3,4-dihydrophthalazin-1(2H)-one in 1 liter of ethanol and the mixture is hydrogenated in a Paar apparatus for 16 hours. The catalyst is filtered off and the filtrate is evaporated to afford the product, 3-(o-aminobenzoyl)-l3,4-dihydro-phthalazin-1(2H)-one, as a colorless solid. Recrystallization from ethanol affords the product as a colorless powder. 
    
    
     ILLUSTRATIVE EXAMPLES 
     Example 1 
     Preparation of 3-(o-Methylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one 
     To 3.3 g (0.022 ml) of 3,4-dihydro-phthalazin-1(2H)-one dissolved in 100 ml of xylene was added 3.9 g (0.022 mol) of N-methylisatoic anhydride and the solution was stirred and heated at reflux under N 2  for 16 hours. The mixture was then cooled to room temperature (about 25° C.) whereupon a heavy precipitate formed. The 3-(o-methylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one was collected as a solid, washed well with xylene to give an off-white powder, mp 199°-202° C. 
     Anal. Calcd. for C 16  H 15  N 3  O 2  : C, 68.31; H, 5.37; N, 14.93. Found: C, 68.27; H, 5.35; N, 14.75. 
     Immunoregulatory activity of the compound, 3-(o-methylaminobenzoyl-3,4-dihydro-phthalazin-1(2H)-one, was assessed by the Kennedy plaque assay [J. C. Kennedy et al, Immunol., 20, 253 (1971)]. In the assay, the change in the number of plaques is a direct correlate of the number of antibody secreting cells in the test animal&#39;s spleen. The results obtained were: 
     
         ______________________________________Dose of the    Percent change inCompound (mg/kg)          the number of plaques______________________________________1.56           -326.25           -4525             -35______________________________________ 
    
     EXAMPLE 2 
     Preparation of 3-(o-Benzylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one 
     3,4-Dihydrophthalazin-1(2H)-one was reacted with N-benzylisatoic anhydride according to the general procedure above to produce 3-(o-benzylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one as a colorless solid, mp 206°-208° C. 
     Anal. Calc. for C 22  H 19  N 3  O 2  : C, 73.93; H, 5.36; N, 11.76. Found: C, 73.91; H, 5.34; N, 11.63. 
     Immunoregulatory activity of the compound, 3-(o-benzylaminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one was assessed by the Kennedy Plaque Assay referred to in Example 1. The results obtained were: 
     
         ______________________________________Dose of the    Percent change inCompound (mg/kg)          the number of plaques______________________________________6.25           +3025             -32______________________________________ 
    
     Example 3 
     Preparation of 3-(o-Aminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one 
     To 7.2 g of 3-(o-benzylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one suspended in 1 liter of EtOH was added 2 g of 10% Pd/C and the mixture was hydrogenated in a Paar apparatus for 16 hours. The catalyst was filtered off and the filtrate evaporated to afford 5.0 g of a colorless solid. Recrystallization from aqueous EtOH afforded 3-(o-amino-benzoyl)-3,4-dihydro-phthalazin-1(2H)-one as a colorless powder in 62% yield; mp 156°-157° C. 
     Anal. Calc. for C 15  H 13  N 3  O 2  : C, 67.40; H, 4.90; N, 15.72. Found: C, 67.22; H, 4.90; N, 15.67. 
     Immunoregulatory activity of the compound, 3-(o-aminobenzoyl)-3,4-dihydro-phthalazin-1(2H)-one was assessed by the Kennedy Plaque Assay referred to in Example 1. The results obtained were: 
     
         ______________________________________Dose of the    Percent change inCompound (mg/kg)          the number of plaques______________________________________1.56           -1825             +10______________________________________ 
    
     ADDITIONAL ILLUSTRATIONS OF COMPOUNDS INCLUDED IN THE INVENTION 
     By following the procedure of Example 1, using the following N-substituted isatoic anhydrides in place of N-methylisatoic anhydride: 
     N-ethylisatoic anhydride, 
     N-isopropylisatoic anhydride, 
     N-butylisatoic anhydride, 
     N-cyclohexylisatoic anhydride, 
     N-(2,3-dimethylphenyl)isatoic anhydride, 
     N-(3-trifluoromethyl)isatoic anhydride, 
     N-phenylisatoic anhydride, the products are, respectively: 
     3-(o-ethylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, 
     3-(o-isopropylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, 
     3-(o-butylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, 
     3-(o-cyclohexylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one, 
     3-[2,3-dimethylphenylamino)benzoyl]-3,4-dihydrophthalazin-1(2H)-one, 
     3-[o-(3-trifluoromethylphenylamino)benzoyl]3,4-dihydrophthalazin-1(2H)-one, and 
     3-(o-phenylaminobenzoyl)-3,4-dihydrophthalazin-1(2H)-one. 
     The above list is not intended to limit the scope of the invention but is included for illustrative purposes only.