Sequential Tandem Four‐Component Reaction for Green Synthesis of Novel Benzo[a]Phenazin‐5‐ol and Pyrimidine‐Tethered Tri‐Substituted Methanes (TRSMs)

ABSTRACT A novel series of benzo[a]phenazin‐5‐ol and pyrimidine‐tethered tri‐substituted methane derivatives ( 6a–k ) was synthesized via a convenient tandem four‐component protocol through a coupling reaction of benzene‐1,2‐diamine ( 1 ), 2‐hydroxy‐1,4‐naphthoquinone ( 2 ), 2‐thiobarbituric acid ( 4 ), and aromatic aldehydes/glyoxylic acid monohydrate 5 in the presence of p ‐toluenesulfonic acid ( p ‐TSOH) as a catalyst in refluxing ethanol. In all reactions, the transformation occurred through the Knoevenagel condensation, Michael addition, and tautomerization sequence of steps. The proposed structures of the synthesized compounds are supported by spectroscopic data (Fourier transform infrared [FT‐IR] spectroscopy, 1 H‐NMR, 1 3 C‐NMR) and mass spectrometry. This green synthetic method offers notable advantages, including simple operation, short reaction times, commercially available reagents, broad substrate scope, easy workup without chromatographic purification, and good to high yields (73%–85%).