1: 3,7-dimethyl xanthine With potassium carbonate in N,N-dimethyl-formamide T=120°C; 1 h; 2: ethylene dibromide in N,N-dimethyl-formamide T=120°C; 1 - 18 h;

sodium hydride in N,N-dimethyl-formamide T=50 - 80°C; 18 h;