Green and mild laccase-catalyzed aerobic oxidative coupling of benzenediol derivatives with various sodium benzenesulfinates

Laccase‐Based Oxidative Catalytic Systems for the Aerobic Aromatization of Tetrahydroquinazolines and Related N‐Heterocyclic Compounds under Mild Conditions

“…Terephthalaldehyde as a bifunctional aromatic aldehyde was satisfactorily subjected to oxidative cyclization as well ( Table 2, entry 14). Although, the exact mechanism is not clear and should be further studied in detail, however, based on our observation during the course of the reaction (Table 1, entries 5, 11) and previously reported mechanisms about application of laccase in oxidation of catechol in tandem reactions [29] and oxidative dehydrogenation of N-heterocyclic rings using catechol as a cocatalyst, [15][16][17] a plausible reaction pathway for the dehydrogenation of 2-substituted tetrahydroquinazolines in the presence of laccase/catechol catalyst system has been proposed in Scheme 2. Mechanism involves oxidation of catechol to obenzoquinone using laccase followed by the reduction of one molecule of oxygen to two molecules of water.…”

A novel magnetically separable laccase‐mediator catalyst system for the aerobic oxidation of alcohols and 2‐substituted‐2,3‐dihydroquinazolin‐4(1H)‐ones under mild conditions

“…Although, the actual role of present cooperative catalyst system is not exactly clear now, however on the basis of previously reported mechanisms for the application of Pd@MCF/BQ catalyst system in the oxidation reactions [ 24,38 ] and aerobic oxidation of HQ to BQ in the presence of laccase, [ 19 ] it is hypothesized that Pd (II) atoms are actual oxidizing agents. After treatment of Laccase with HQ, the active Pd (II) atoms required for the oxidation reaction are generated through adsorption of BQ to the Pd(0) nanoparticles in Pd‐Laccase@MMCF [ 38 ] (Scheme 4).…”

“…Based on the mentioned background and our systematic studies about the application of laccase and laccase/quinone catalytic system in organic reactions, [ 19 ] our main objectives in this study are: (1) the synthesis of a magnetically separable cooperative catalyst system via the immobilization of Pd nanoparticles as a strong oxidizing catalyst and laccase enzyme as an oxygen‐activating and sustainable alternative to transition metal complex on MMCF (Pd‐Laccase@MMCF); and (2) the investigation of the catalytic ability of this biohybrid catalyst for the aerobic oxidation of alcohols and 2‐substituted‐2,3‐dihydroquinazolin‐4(1 H )‐ones in the presence of hydroquinone instead of benzoquinone as electron transfer mediator (Scheme 2). One of the main novelty and advantage of this cooperative catalytic system is that redox catalysts are immobilized on magnetically reusable support.…”

Dioxygen Activation by Laccases: Green Chemistry for Fine Chemical Synthesis

“…The yield of most of the compounds synthesized by laccase Suberase was lower than those previously synthesized by other commercial laccases[Hajdok et al [49];Witayakran et al (2007);Witayakran and Ragauskas (2009)]. Nonetheless, two of the Suberase laccase-synthesized compounds reported byWellington et al [32] were obtained in higher yields than those obtained by fungal crude extract, chemical or electrochemical methods[43][44][45][46][47]. The contribution of Wellington et al [32], with respect to the other authors that synthesized the same 5,6-dihydroxylated benzo[b]furans (Figure 4Ac), is the evaluation of cytostatic and cytotoxic effect of the compounds against TK10 (renal), UACC62 (melanoma), MCF7 (breast), HeLA (cervical) cancer cell lines.…”