A facile microwave assisted synthesis and structure elucidation of (3R)-3-alkyl-4,1-benzoxazepine-2,5-diones by crystallographic, spectroscopic and DFT studies

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 230; p. 117995
• Main Authors: Raza, Abdul Rauf, Nisar, Bushra, Khalid, Muhammad, Gondal, Humaira Yasmeen, Khan, Muhammad Usman, de Alcântara Morais, Sara Figueirêdo, Tahir, Muhammad Nawaz, Braga, Ataualpa Albert Carmo
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 05.04.2020
• Subjects: (3R)-3-alkyl-4,1-benzoxazepine-2,5-diones; Chiral pool approach; DFT; Microwave irradiation; N-acylanthranilic acids; Spectroscopic data; Microwave irradiation; N-acylanthranilic acids; DFT; (3R)-3-alkyl-4,1-benzoxazepine-2,5-diones; Chiral pool approach; Spectroscopic data
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2019.117995

The use of microwave (MW) irradiation in organic synthesis has become increasingly popular within the pharmaceutical and academic arenas because it is a new enabling technology for drug discovery and development. It is a rapid way of synthesis, which involves faster reaction rates and high selectivity to conventional heating method of syntheses. The MW-assisted 7-exo-tet cyclization of N-acylanthranilic acids afforded (3R)-3-alkyl-4,1-benzoxazepines-2,5-diones in very short duration (20 min) with extraordinary high yields in comparison to conventional heating mode of synthesis. The method development, comparative yields of MW-assisted and thermal method of syntheses, crystallographic, spectroscopic and density functional theory (DFT) studies are reported herein. Four novel compounds with chemical formulas C10H9BrClNO35m, C19H19NO36e, C13H14ClNO36h and C12H11Br2NO36h were synthesized, validated by 1HNMR, 13CNMR, FT-IR, UVVis, EIMS spectroscopic techniques and confirmed by using single crystal X-ray diffraction (SC-XRD) study. The DFT and TDDFT calculations at B3LYP/6-311 + G(d,p) level of theory were performed for comparative analysis of spectroscopic data, optimized geometries, frontier molecular orbitals (FMOs), natural bond orbital (NBO) analysis and nonlinear optical (NLO) properties of 5m, 6e, 6h and 6o. Overall, experimental findings were supported nicely by corresponding DFT computed results. The NBO analysis confirmed that the presence of non-covalent interactions, hydrogen bonding and hyper- conjugative interactions are pivotal cause for the existence of 5m, 6e, 6h and 6o in the solid-state. NLO analysis showed that 5m, 6e, 6h and 6o have significant NLO properties as compared to prototype standard compound which disclosed their potential for technology related applications. [Display omitted] •Four novel (3R)-3-alkyl-4,1-benzoxazepine-2,5-dione derivatives were synthesized by facile microwave assisted synthesis.•SC-XRD, 1H NMR, 13C NMR, FT-IR and UV–Vis were performed for the characterization.•Computational study was done at B3LYP/6-311 + G(d,p) level for comparative analysis.•Comparative study reveals a good agreement between experimental and DFT results.•FMOs, NBO analysis and nonlinear optical (NLO) properties were calculated.