Heterocyclic studies. Part XXI. Synthesis and covalent hydration of some 2-substituted 4-trifluoromethylpteridines

Abstract

Syntheses of eight 2-substituted 4-trifluoromethylpteridine derivatives [(1; X = Cl, NH₂, NMe₂, OMe, OEt, SMe, or NH·CH₂Ph) and (VI; X = CF₃)] are described. The 2-thione (VI; X = CF₃) was obtained as a 3,4-covalently hydrated species which could not be dehydrated. The rest of the compounds formed equilibrium mixtures with their 3,4-hydrates in aqueous solution, but the position of the equilibrium varied widely with the nature of the 2-substituent. 3,4-Hydrated cations were formed in acidic solutions but, in some cases, only after transformation of more rapidly formed 5,6,7,8-dihydrated cations.