A peroxo‐Mo(VI)/Mo(VI)‐mediated redox synthesis of quinazolin‐4(3H)‐ones and their aggregation‐induced emission property and mechanism

Abstract

An efficient method based on peroxo-Mo(VI)/Mo(VI) redox cycle for ambienttemperature synthesis of quinazolin-4(3H)-ones has been developed. Catalytic phosphomolybdic acid (PMA) exhibits Lewis acid and oxidative dehydrogenation activities at different phases of the reaction, and the true oxidative catalytic species was identified as peroxo-Mo(VI) Keggin cluster. Surprisingly, we found that aggregation-induced emission (AIE) is a generic property that has long been neglected for quinazolin-4(3H)-ones. Theoretical calculation results well rationalized their photophysical behaviors and elucidated their AIE mechanism as restriction of access to dark state (RADS). The crystallographic analysis of two representative quinazolin-4(3H)-ones not only revealed their packing mode and weak intermolecular actions but also supported the molecular conformations obtained by theoretical calculations.

Structural Regulation of Two Polyoxometalate-Based Metal–Organic Frameworks for the Heterogeneous Catalysis of Quinazolinones

“…The attracted 2-aminobenzamide could react with a to afford an imine-type intermediate b , and thus the intermediate b further underwent an intramolecular cyclization process under the catalysis of Lewis acidic sites on catalysts, resulting in the 2-phenyl-2,3-di-hydroquinazolinone intermediate c . On the other hand, the {ε- Zn 4 PMo 12 } dimeric units are activated by TBHP to afford the active species with peroxo sites, which could activate the c to undergo rapid oxidation and afford the final quinazolinone product. After that, the peroxo-{ε- Zn 4 PMo 12 } catalysts were reduced back to the original state for the next round.…”

“…50−52 The presence of catalysts SDUT-21 and SDUT-22 and the constructed ligands on catalysts would be conducive to attracting 2-aminobenzamide molecules by active sites getting into the cavities of the catalysts, which are large enough for the accommodation of two substrates to contact each other within the well-confined microenvironment and the Lewis active sites Zn(II) ions on the POM moiety to coordinate to the aldehyde, forming the intermediate a. The attracted 2-aminobenzamide could react with a to afford an imine-type intermediate b, and thus the intermediate b further underwent an intramolecular cyclization process under the catalysis of Lewis acidic sites on catalysts, resulting in the 2-phenyl-2,3-di-hydroquinazolinone intermediate c. On the other hand, the {ε-Zn 4 PMo 12 } dimeric units are activated by TBHP to afford the active species with peroxo sites, 53 which could activate the c to undergo rapid oxidation and afford the final quinazolinone product. After that, the peroxo-{ε-Zn 4 PMo 12 } catalysts were reduced back to the original state for the next round.…”