Photoinduced organic reactions by pyrene catalysts

Pyrene is one of the most attractive polycyclic aromatic hydrocarbons (PAHs) in photochemistry. Based on their redox properties, pyrenes have potential as photosensitizers. In this review, we aim to summarize recent developments in pyrene-catalyzed photoinduced organic reactions via the process of energy transfer or single electron transfer based on the excited state of pyrenes. 1. Introduction 2. Photolysis involving N–O bond cleavage or decarboxylation 3. (Cyclo)addition reactions with styrenes 4. Transformations via cleavage of C–F, C–I, C–S, and C–N bonds 5. Reactions based on sensitization-initiated electron transfer (SenI-ET) 6. Miscellaneous transformations 7. Conclusion

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

Metal-catalyzed hydrofunctionalization reactions of alkynes, i.e., the addition of Y–H units (Y = heteroatom or carbon) across the carbon–carbon triple bond, have attracted enormous attention for decades since they allow the straightforward and atom-economic access to a wide variety of functionalized olefins and, in its intramolecular version, to relevant heterocyclic and carbocyclic compounds. Despite conjugated 1,3-diynes being considered key building blocks in synthetic organic chemistry, this particular class of alkynes has been much less employed in hydrofunctionalization reactions when compared to terminal or internal monoynes. The presence of two C≡C bonds in conjugated 1,3-diynes adds to the classical regio- and stereocontrol issues associated with the alkyne hydrofunctionalization processes’ other problems, such as the possibility to undergo 1,2-, 3,4-, or 1,4-monoadditions as well as double addition reactions, thus increasing the number of potential products that can be formed. In this review article, metal-catalyzed hydrofunctionalization reactions of these challenging substrates are comprehensively discussed.

CHARACTERIZATION OF PREDICTED BACTERIAL COLD-ADAPTED LIPASE FROM SEAFOOD COLD STORAGE

Lipases constitute as top three most important group of enzymes along with carbohydrases and proteases, and are widely used in various industries. In particular, lipase that perform high activity at low temperatures, or referred as cold adapted lipase (CLPs) considered as attractive catalyst due to its activity at low temperature. This unique feature is the main advantage of cold adapted lipase utilization because it requires a low energy source that is correlated with lower production costs and energy. In addition, reactions occur in cold temperatures may result in better product quality. The purpose of this research was to perform screening and characterization of bacterial cold adapted lipase from seafood cold storage. Among 53 isolates, Kr_16_30, TI_37_14 and Kr_16_28 showed the highest activity with 4.12 U/mL; 3.87 U/mL and 3.21 U/mL, respectively. Isolates Kr_16_30 seemed to be typical cold adapted lipase with optimum temperature at 20°C and pH 7. Isolates Kr_16_28 performed highest lipolytic activity at 30°C while TI_37_14 suspected to be similar to typical mesophilic lipase with optimum temperature at 40°C. Species identification based on 16s rRDA sequencing revealed that isolates Kr_16 30 and Kr_16 28 are belong to genus Pseudomonas and Bacillus, repectively.

Organo-catalysis as emerging tools in organic synthesis: aldol and Michael reactions

Organocatalysis has occupied sustainable position in organic synthesis as a powerful tool for the synthesis of enantiomeric-rich compounds with multiple stereogenic centers. Among the various organic molecules for organocatalysis, the formation of carbon–carbon is viewed as a challenging issue in organic synthesis. The asymmetric aldol and Michael addition reactions are the most significant methods for C–C bond forming reactions. These protocols deliver a valuable path to access chiral molecules, which are useful synthetic hybrids in biologically potent candidates and desirable versatile pharmaceutical intermediates. This work highlighted the impact of organocatalytic aldol and Michael addition reactions in abundant solvent media. It focused on the crucial methods to construct valuable molecules with high enantio- and diastereo-selectivity.

7 Electrochemically Generated Nitrogen-Centered Radicals

Nitrogen-centered radicals are versatile reactive intermediates for organic synthesis. This chapter describes recent progress in the electrochemical generation and reactions of nitrogen-centered radicals. Under electrochemical conditions, various nitrogen-centered radicals are generated through electrolysis of readily available precursors such as N—H bonds or azides. These reactive intermediates undergo addition reactions to π-systems or hydrogen-atom abstraction to generate various nitrogen-containing compounds.

Cephalexin Degradation Initiated by OH Radicals: Theoretical Prediction of the Mechanisms and the Toxicity of Byproducts

In this work, density functional theory is used to study the local reactivity of cephalexin (CLX) to radical attack and explain the mechanism of the reaction between CLX and hydroxyl radical attack leading to degradation byproducts. The reaction between •OH and CLX is supposed to lead to either an addition of a hydroxyl radical or an abstraction of a hydrogen. The results showed that the affinity of cephalexin for addition reactions increases as it passes from the gas to the aqueous phase and decreases as it passes from the neutral to the ionized form. Thermodynamic data confirmed that OH addition radicals (Radd) are thermodynamically favored over H abstraction radicals (Rabs). The ecotoxicity assessments of CLX and its byproducts are estimated from the acute toxicities toward green algae, Daphnia and fish. The formation of byproducts is safe for aquatic organisms, and only one byproduct is harmful to Daphnia.