Reaction Mechanism in Aromatic Heterocyclic Compounds. XI. : Reaction of Nitroquinoline with Sodium Hypobromite Solution. I. : 3-Nitroquinoline (Organic)

Abstract

3-Nitroquinoline (I) was reacted with aqueous sodium hypobromite in methanolic KOH at definite temperature (37-40° for condition A, 0-5° for condition B, and -40--35° for condition C). The products obtained under these conditions were 3-bromo-4-methoxyquinoline (IIa), 3, 6, 8-tribromo-4-methoxyquinoline (IIb), 3-bromo-2, 4-dimethoxyquinoline (IIIa), 3, 6-dibromo-2, 4-dimethoxyquinoline (IIIb), 3, 6, 8-tribromo-2, 4-dimethoxyquinoline (IIIc), 2, 4-dimethoxy-3-nitroquinoline (IVa), 6-bromo-2, 4-dimethoxy-3-nitroquinoline (IVb), 2, 4, 6-tribromoaniline (Va), and 2, 4, 6-tribromo-3-methoxyaniline (Vb). Similarly, the reaction of 2-alkoxy-3-nitroquinoline (VII, 2-CH₃O, VIII, 2-C₂H₅O) gave 2-alkoxy-3-bromo-4-methoxyquinoline (IIIa ; IX) and 2-alkoxy-4-methoxy-3-nitroquinoline (IVa ; X). The same reaction of 2-alkoxy-4-methoxy-3-nitroquinoline (IVa, 2-CH₃O, X, 2-C₂H₅O) gave 2-alkoxy-3-bromo-3, 4-dihydro-4, 4-dimethoxy-3-nitroquinoline (XI ; XII). This reaction was discussed as an addition-elimination mechanism involving CH₃O^- addition at the 4-position of I, followed by bromination at the 3-position and elimination of HNO₂ o HBr.