A concise synthesis of a highly substituted 6‐(1 H H ‐benzimidazol‐1‐yl)‐5‐nitrosopyrimidin‐2‐amine: synthetic sequence and the molecular and supramolecular structures of one product and two intermediates

摘要

A concise and efficient synthesis of 6‐benzimidazolyl‐5‐nitrosopyrimidines has been developed using Schiff base‐type intermediates derived from N 4 ‐(2‐aminophenyl)‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine. 6‐Methoxy‐ N 4 ‐{2‐[(4‐methylbenzylidene)amino]phenyl}‐5‐nitrosopyrimidine‐2,4‐diamine, (I), and N 4 ‐{2‐[(ethoxymethylidene)amino]phenyl}‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine, (III), both crystallize from dimethyl sulfoxide solution as the 1:1 solvates C 19 H 18 N 6 O 2 ·C 2 H 6 OS, (I a ), and C 14 H 16 N 6 O 3 ·C 2 H 6 OS, (III a ), respectively. The interatomic distances in these intermediates indicate significant electronic polarization within the substituted pyrimidine system. In each of (I a ) and (III a ), intermolecular N—H…O hydrogen bonds generate centrosymmetric four‐molecule aggregates. Oxidative ring closure of intermediate (I), effected using ammonium hexanitratocerate(IV), produced 4‐methoxy‐6‐[2‐(4‐methylphenyl‐1 H ‐benzimidazol‐1‐yl]‐5‐nitrosopyrimidin‐2‐amine, C 19 H 16 N 6 O 2 , (II) [Cobo et al. (2018). Private communication (CCDC 1830889). CCDC, Cambridge, England], where the extent of electronic polarization is much less than in (I a ) and (III a ). A combination of N—H…N and C—H…O hydrogen bonds links the molecules of (II) into complex sheets.