Complete reaction pathway of prebiotic reactions for formation of the purine nucleobases adenine, hypoxanthine, guanine, isoguanine, 2,6‐diaminopurine, and xanthine from pure formamide are presented. All reactants (hydrogen cyanide, ammonia, water, formic acid, urea) and catalysts (formamide and formimidic acid) needed in the self‐catalyzed reactions are available from a starting compound, formamide. The required raw materials are obtained by partial decomposition of formamide.