O-Arylation of Angular Diazaphenoxazine and Related Carbocyclic Analogue Using Buchwald Catalyst
Synthesis of twelve O-arylated diazabenzo[a]phenoxazine-5-one and its carbocyclic analogue is reported in 46 – 99 % yields. The intermediates were prepared by anhydrous base catalyzed reaction of 2,3-dichloro-1,4-naphthoquinone with 4,5-diamino-6-hydroxyl-2-mercaptopyrimidine and 2-aminophenol. The O-arylation process occurred smoothly in non-polar solvent, toluene with the inexpensive base, K2PO4 at 110oC. The intermediates were combined with a variety of electron-deficient, electrically neutral and electron-rich phenols in the presence of a catalyst combination of Pd(OAc)2 and electron rich, bulky alkyldiarylphosphine ligand in which the alkyl groups are tert-butyl (t-Buxphos), to furnish the arylated compounds. Bulky yet basic nature of the phosphine ligand is thought to be responsible for these transformations. The highest yields were obtained when the intermediates coupled with electron rich phenols, with the carbocyclic analogue giving better yields. IR, 1H NMR and 13C NMR spectra data, confirmed the structures of all the synthesized compounds. The effect of the synthesized compounds on bacteria and fungi growth was studied. The studied compounds were found to be potent antibacterial and antifungal agents as they showed significant biological activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans. In addition, they may be useful as dyes in industries since they absorb in the UV- visible region.
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