A simple and novel protocol for the facile synthesis of bicyclic hybrid molecular framework of morpholinopyrimidines having six-membered pyrimidine rings fused with the morpholine unit is established. The method has been successfully employed to synthesize both regioisomers of the morpholinopyrimidine derivatives in good to high yields. The strategy is further extended successfully to synthesize bicyclic pyrimidooxazapine derivatives bearing the six-membered aromatic pyrimidine unit fused with seven-membered aliphatic oxazapine fragment.

New tricyclic benzimidazoles have been synthesized by condensation of 3,4-dihydro-2H-benzo [b][1,4]oxazin-5-amine and different aldehydes in presence of sodium metabisulfite adsorbed on silica. The method is very efficient, and reactions are completed at room temperature with easy product isolation. The synthesized compounds showed antimicrobial potential against gram-positive bacteria S. aureus and gramnegative bacteria E. coli with MIC of 0.625 mg/ml for com-pounds 6 f (cyclohexyl substituent) and 6 h (furan substituent) and 0.312 mg/ml for compound 6 c (chlorophenyl substituent) respectively, were evaluated by Resazurin microtiter plate visual method. Molecular docking studies using Autodock 4.2 showed theoretical binding energy À 6.74 to À 8.32 Kcal/mol for S. aureus and À 5.94 to À 8.01 Kcal/mol for E. coli with PDB Id 2W9S and 2EX6 respectively.