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The (Z)-2-methoxyimino-2-(furyl-2-yl) acetic acid ammonium salt (SMIA) is a key intermediate used for the synthesis of cefuroxime. The current conventional chemical synthesis of SMIA shows some disadvantages, such as high cost and environmental pollution. In this study, we have proposed an alternative route to prepare SMIA from 2-furylhydroxymethylketone (2-FHMK), in which a biocatalyst was used to replace the traditional chemical synthesis of 2-acetylfuran utilizing furfural and formaldehyde as raw materials. Thiamine diphosphate (ThDP)-dependent enzymes were initially screened and assembled in Escherichia coli. Pyruvate decarboxylase from Sulfobacillus sp. hq2 (SsPDC) was identified as the optimal enzyme among the 21 enzymes screened. Furthermore, the enzyme-catalyzed synthesis of 2-FHMK was optimized and an MBP tag was used to increase its solubility and improve the catalytic efficiency of SsPDC. Finally, 63 g L−1 2-FHMK was produced in a 1-L reactor (96.2% yield, 5.25 g L−1 h−1 space-time yield). This route provides a promising alternative for the low-cost and green production of SMIA on an industrial scale and provides another strategy for the reuse of formaldehyde and furfural. [ABSTRACT FROM AUTHOR]

The iridium‐catalyzed cycloisomerization of various alkynoic acids was successfully developed, and a series of five‐, six‐, and especially seven‐membered unsaturated lactones were constructed with moderate yields and excellent regioselectivities (up to 68% yield, >99:1 rr). In addition, the indole compound can be easily prepared with 75% yield through this efficient synthetic methodology. Moreover, a plausible mechanism for this Ir‐catalyzed cycloisomerization of alkynoic acids was proposed. [ABSTRACT FROM AUTHOR]

Chiral benzoxazinones and 4 H -3,1-benzoxazines as important motifs are widely found in abundant pharmaceuticals and biological molecules. We herein successfully developed the first kinetic resolution (KR) process of racemic benzoxazinones through Ir-catalyzed asymmetric intramolecular allylation, furnishing a wide range of chiral benzoxazinones and 4 H -3,1-benzoxazines with excellent results via outstanding KR performances (with the s factor up to 170). This protocol exhibited broad substrate scope generality and good functional group tolerance, and the chiral 4 H -3,1-benzoxazine products could be readily transformed to other useful optically active heterocycles.

Benzoic acid (BA) is one of the most common organic acids in the Earth's atmosphere and an important component of atmospheric aerosol particles. The reaction mechanism of OH, NO 3 and SO 4 - radicals with BA in atmospheric water droplets and that of OH radicals with BA in the atmosphere were studied in this paper. The results show that in atmospheric water droplets the potential barriers of the elementary addition reactions of BA with OH radicals are lower than those of elementary abstraction reactions, and the potential barriers of OH-initiated reactions are less than for NO 3 and SO 4 - reactions. The initiation reactions of OH radicals and BA are exothermic, but the abstraction reactions of NO 3 and SO 4 - are endothermic processes. Among the products, 6-hydroxybenzoic acid (6-HBA) and 4,6-dihydroxybenzoic acid (4,6-DHBA) are the most stable, while 3-hydroxybenzoic acid (3-HBA) and 3,5-dihydroxybenzoic acid (3,5-DHBA) are much less stable and, thus, much less abundant compared to 6-HBA and 4,6-DHBA. The initiation and subsequent degradation of BA with OH radicals in the gas phase were calculated. The products of addition and abstraction reactions of BA with OH radicals can be further oxidized and degraded by O 2 /NO. According to the results of kinetic calculations, the total reaction rate constant of OH radicals with BA at 298.15 K in atmospheric water droplets is 2.35 × 10 -11 cm 3 per molecule per s. The relationship between reaction rate constants, temperature and altitude were also investigated and discussed in the present study., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)