Synthesis and characterization of materials derived from 4,5-dicyanoimidazoles.

Abstract

Synthesis of l-methyl-2-fluoro-4,5-dicyanoimidazole was accomplished by halogen exchange between 1-methyl-2-bromo-4,5-dicyanoimidazole and potassium fluoride with catalytic 18-crown-6 ether in diglyme. Halogen exchange between l-methyl-2-bromo-4,5-dicyanoimidazole and lithium chloride in N-methylpyrrolidinone at 150$\sp\circ$C yielded 1-methyl-2-chloro-4,5-dicyanoimidazole, while additional heating to 210$\sp\circ$C resulted in the subsequent demethylation to yield 2-chloro-4,5-dicyanoimidazole. Thermolyses of the 2-halo-4,5-dicyanoimidazole derivatives (F, Cl), and 1-iodo-2-halo-4,5-dicyanoimidazole derivatives (Cl, Br, I) between 100-290$\sp\circ$C were found to yield Tris(imidazo)(1,2-a:1,2-c:1,2-e) -1,3,5-triazine- 2,3,5,6,8,9-hexacarbonitrile, or HTT, with (C$\sb5$N$\sb4$)$\sb3$ composition. HTT has been characterized, purified, and the crystal structure obtained. HTT crystallized in a monoclinic crystal system in a P2$\sb1$/n(#14) space group. Thermolysis of HTT at 490-500$\sp\circ$C resulted in a carbon nitrogen (C-N) material with C/N = 1.020, while the thermolysis of HTT at 1070$\sp\circ$C resulted in a carbonaceous material. Isothermal analyses at 400$\sp\circ$C under nitrogen indicate 3.4, 2.7 and 4.5 % wt.loss/h respectively for HTT, the C-N material and the carbonaceous material. Nucleophilic aromatic substitution on 1-methyl-2-fluoro-4,5-dicyanoimidazole with the potassium salts of 4,5-dicyanoimidazole derivatives has resulted in the synthesis of several 1-methyl-2-(4,5-dicyano-1-imidazolyl)-4,5-dicyanoimidazole derivatives. Chlorination of 1-methyl-2-(2-amino-4,5-dicyano-1-imidazolyl)-4,5-dicyanoimidazole was accomplished by diazotization in hydrochloric acid followed by decompostion, additional treatment with phosphoryl oxychloride yielded 1-methyl-2-(2-chloro-4,5-dicyano-1- imidazolyl)-4,5-dicyanoimidazole. The 1-methyl-2-(4,5-dicyano-1-imidazolyl)-4,5-dicyanoimidazole derivatives were further modified by demethylation with lithium chloride in N,N-dimethylacetamide. The thermolyses of several 2-(4,5-dicyano-1-imidazolyl)-4,5-dicyanoimidazole derivatives were examined.