Abstract 2-Amino-N-heterocycles, such as 2-aminopyridine 7 or 2-aminobenzimidazole 16 as well as benzamidines 19 possessing a N-(4-nitrobenzyl)-substituent react as NCNC- synthons with formamide chlorides 5, formamide acetals 2 or acetic anhydride (C 1-building