Synthesis of some novel halogenated 2,4‐diaminoquinazolines

Abstract

AbstractThree new 2,4‐diaminoquinazolines, the 5,6‐difluoro, 6,7‐difluoro and 7,8‐difluoro isomers were prepared by the reaction of the requisite trifluorobenzonitrile and guanidine carbonate. Surprisingly, 2,3,6‐trifluorobenzonitriles gave 2,4‐diamino‐5,6‐difluoroquinazoline exclusively as determined by high resolution nuclear magnetic resonance spectroscopy. On the other hand, 3‐amino‐2,6‐difluorobenzonitrile on reaction with guanidine carbonate yielded only 5‐fluoro‐2,4,8‐triaminoquinazoline. This compound was subsequently converted to 8‐chloro‐2,4‐diamino‐5‐fluoroquinazoline using the Sandmeyer procedure. The nitration of 2,4‐diamino‐8‐fluoroquinazoline occurred exclusively at position six yielding 2,4‐diamino‐8‐fluoro‐6‐nitroquinazoline, which upon reduction with stannous chloride afforded 8‐fluoro‐2,4,6‐triaminoquinazoline. In a similar fashion 7‐fluoro‐2,4‐diaminoquinazoline underwent nitration at position six and was then reduced to give 7‐fluoro‐2,4,6‐triaminoquinazoline. Finally, both of these triaminoquinazolines were converted to the 6‐chloro derivatives under Sandmeyer conditions to yield 6‐chloro‐2,4‐diamino‐8‐fluoroquinazoline and 6‐chloro‐2,4‐diamino‐7‐fluoroquinazoline, respectively.