10.1016/j.crci.2016.03.008
This research investigates the impact of metal-induced Lewis acidity on the catalytic activity of zeolites in the Friedel-Crafts acylation of anisole with propanoic acid. The study prepared acid catalysts including Ni, Ag, and Fe-loaded zeolites of different structures (BEA and MFI) via cationic exchange or impregnation techniques from pristine H-zeolites. The results showed that regardless of the doping procedure, the introduction of transition metals led to a significant decrease in propanoic acid conversion, with the detrimental effect following the order: Ag? > Ni2? > Fe3?. In contrast, pristine acidic zeolites, particularly H-ZSM-5, were found to be the most active and selective, with the highest intrinsic activity (TOF values of 0.09 h?1).
10.1016/S0022-328X(96)06489-3
The research investigates the catalytic synthesis of 4-methylcoumarin from ortho-iodophenyl 3-butenoate using palladium complexes. The purpose is to control the ring closure and isomerization processes to achieve high yields of the desired cyclic compound. Key chemicals involved include palladium(0) complexes, such as Pd(dba)2 and Pd(PPh3)4, along with ligands like triphenylphosphine and bis(diphenylphosphino)ferrocene (dppf), solvents like anisole and dimethylformamide (DMF), and neutralizing agents like potassium butyrate and magnesium oxide. The study concludes that by carefully selecting ligands, solvents, and neutralizing agents, and by controlling reaction conditions, it is possible to achieve quantitative yields of 4-methylcoumarin. Specifically, the use of dppf in conjunction with Pd(PPh3)4 in DMF with MgO under nitrogen resulted in a 100% yield of the desired product, demonstrating effective control over the competing reactions.
10.1021/acs.orglett.1c01720
The study presents an efficient method for the trifluoromethylation of benzoic acids using TMSCF3 (trimethylsilyl trifluoromethane) to produce aryl trifluoromethyl ketones. The reaction involves anhydrides as in situ activating reagents, with trifluoroacetic anhydride (TFAA) and 4-dimethylaminopyridine (DMAP) playing crucial roles in activating the carboxylic acids and facilitating nucleophilic addition. CsF (cesium fluoride) is used to enhance the yield of the desired products. The reaction is conducted in PhOMe (anisole) solvent under nitrogen at 120 °C for 15 hours. The study demonstrates a wide substrate scope, including various carboxylic acids with different functional groups, and shows high functional group tolerance. Notably, bioactive molecules such as adapalin, probenecid, and telmisartan can also be trifluoromethylated using this method, highlighting its potential in drug design and development. The reaction conditions are relatively mild, and the process is scalable, making it a practical and environmentally benign approach for synthesizing aryl trifluoromethyl ketones.
10.7164/antibiotics.53.1305
The study focuses on the synthesis and antibacterial activities of novel C(3)-aminopyrimidinyl substituted cephalosporins. Cephalosporins are widely used antibiotics, but many have become ineffective against respiratory tract infections due to resistance issues, particularly from penicillin-resistant Streptococcus pneumoniae (PRSP). To address this, researchers introduced a vinyl spacer at the C-3 position of the cephem nucleus and synthesized new cephalosporins with a C(3) substituted aminopyrimidinyl group. The synthesis involved coupling acid 3 with 7-ACLE in the presence of pyridine and phosphorous oxychloride to form intermediate 5, which was then reacted with nucleophiles (pyrimidinylthiol group) in DMF. The protecting groups were removed using trifluoroacetic acid (TFA) and anisole to obtain the final cephalosporins. Another series of compounds was prepared from chloride 5 via allyl chloride 6, using a Wittig reagent and subsequent displacement reactions. The synthesized compounds were tested for their antibacterial activities against various bacterial strains, including Gram-positive and Gram-negative bacteria, and showed improved activities against respiratory tract pathogens compared to the reference antibiotic cefdinir.
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