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A mild process for the selective oxidation of sulfides is in great demand. Therefore, probing the mechanism underlying the biological oxidation of sulfides under ambient conditions may provide valuable insights for the development of such a reaction. Based on porphyrin models of P450 enzymes, evidence of two key intermediates, Int0 and Int1, in this reaction is provided. Spectroscopic studies indicated the formation of a hydroperoxide-iron(III) species (Int0) upon addition of H(2)O(2). This intermediate proved to be highly selective for sulfoxide production. By contrast, a defined porphyrin oxoiron(IV) cation radical (Int1) directly reacted with sulfoxides, leading selectively to the corresponding sulfones. Interestingly, the available sulfoxides reversibly act as a new axial ligand for Int0 forming a more active species Int0(SO). The amount of Int0 increased in the presence of alkyl, aryl, or aromatic sulfides, while Int1 formed in the absence of these sulfides. Thus, sulfoxides and sulfones would selectively form under conditions that favor the corresponding intermediates, which elucidate the biological oxidation pathway.

The catalytic oxidative desulfurization (ODS) of dibenzothiophene (DBT) in decahydronaphthalene (decalin) was performed using the oil-soluble oxidant cyclohexanone peroxide (CYHPO) with a molybdenum oxide (MoO3) catalyst supported on macroporous polyacrylic cationic exchange resin D113 of weak acid series. The influence of the reaction temperature, reaction time, the molar ratio of CYHPO/DBT, and catalyst reuse was investigated in detail. In the presence of the catalyst MoO3/D113, the conversion of DBT to DBT sulfone was up to 100% at 100 °C in 40 min. The ODS was performed using other oil-soluble alkyl peroxides, i.e., tert-butyl hydroperoxide (TBHP) and tert-amyl hydroperoxide (TAHP), in comparison with the oxidative activity of CYHPO. The results showed that the activity of alkyl peroxides decreases in the order CYHPO > TAHP > TBHP, reversing the order of the peroxy oxygen electronic density. The oxidation mechanism is then discussed.

The synthesis of urea fertilizer is currently the largest CO 2 conversion process by volume in the industry. In this process, ammonium carbamate is an intermediate en route to urea formation. We determined that the tetraammineaquacopper(II) sulfate complex, [Cu(NH 3 ) 4 (OH 2 )]SO 4 , catalyzed the formation of urea from ammonium carbamate in an aqueous solution. A urea yield of up to 18 ± 6% was obtained at 120 °C after 15 h and in a high-pressure metal reactor. No significant urea formed without the catalyst. The urea product was characterized by Fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), and quantitative 1 H{ 13 C} NMR analyses. The [Cu(NH 3 ) 4 (OH 2 )]SO 4 catalyst was then recovered at the end of the reaction in a 29% recovery yield, as verified by FT-IR, PXRD, and quantitative UV−vis spectroscopy. A precipitation method using CO 2 was developed to recover and reuse 66 ± 3% of Cu(II). The catalysis mechanism was investigated by the density functional theory at the B3LYP/6-31G** level with an SMD continuum solvent model. We determined that the [Cu(NH 3 ) 4 ] 2+ complex is likely an effective catalyst structure. The study of the catalysis mechanism suggests that the coordinated carbamate with [Cu(NH 3 ) 4 ] 2+ is likely the starting point of the catalyzed reaction, and carbamic acid can be involved as a transient intermediate that facilitates the removal of an OH group. Our work has paved the way for the rational design of catalysts for urea synthesis from the greenhouse gas CO 2 .

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The present research has demonstrated that selective C−S bond cleavages of dibenzothiophene and its derivatives are feasible by thia‐Baeyer–Villiger type oxidation, i. e. the oxygen insertion process within a sulfoxide‐carbon linkage, in the presence of porphyrin iron (III) and by ultraviolet irradiation originating from sunlight, high pressure Hg‐lamp or residentially germicidal ultraviolet lamp under very mild conditions. This reaction with tert‐butylhydroperoxide at 30.0 °C leads to dibenzo[1,2]oxathiin‐6‐oxide (PBS) in 83.2 % isolated yield or its hydrated products, 2‐(2‐hydroxyphenyl)‐benzenesulfinic derivatives (HPBS) in near 100 % yield based HPLC data. PBS and HPBS are a type of biological products detected on the C−S bond cleavage step through various oxidative biodesulfurization (OBDS) pathways, and are useful synthetic intermediates and fine chemicals. These observations may contribute on understanding delicately molecular aspect of OBDS in the photosynthesis system, expanding the C‐S cleavage chemistry of S‐heterocyclic compounds and approaching toward biomemic desulfurization with respect to converting sulfur contaminants to chemically beneficial blocks as needed and performing under the ambient conditions.