10.1016/S0040-4020(01)81729-4
The research investigates the reaction of nitroalkanes with electrophilic alkenes, specifically α,β-unsaturated ketones and α,β-unsaturated nitro compounds, in the presence of alumina-supported potassium fluoride in acetonitrile. The study found that secondary nitroalkanes react with α,β-unsaturated ketones to produce 4,5-dihydrofurans in high yields, while 1-nitropropane reacts with these ketones to yield a mixture of 4,5-dihydrofurans and furans. Additionally, nitroalkenes react with nitroalkanes to form isoxazoline N-oxides. The alumina-supported potassium fluoride acts as an effective catalyst for these reactions, facilitating the formation of the desired products. The study also explores the reaction mechanisms and provides detailed structural analysis of the synthesized compounds using techniques like 1H and 13C NMR spectroscopy.
10.1055/s-1995-3946
The research investigates the use of potassium fluoride-poly(hydrogen fluoride) salts (MFm(HF)n) as fluorinating agents for the halofluorination of alkenes. These salts are solid reagents that can be easily prepared from potassium fluoride and anhydrous hydrogen fluoride. The study demonstrates that these salts efficiently facilitate the halofluorination of alkenes in a regio- and stereoselective manner when used with halonium ion sources such as N-halosuccinimides or 1,3-dibromo-5,5-dimethylhydantoin. The reaction readily proceeds with various alkenes, yielding vicinal halofluorides in good yields. The potassium fluoride-poly(hydrogen fluoride) salts, along with the halonium ion sources and alkenes, play crucial roles in this research, enabling the synthesis of organofluorine compounds with high selectivity and efficiency.
10.1016/0040-4020(96)00480-2
The research focused on the cyclization of o-hydroxyphenyl ethynyl ketones, aiming to develop efficient synthetic methods for the construction of 2-substituted pyranones, which possess significant biological activities. The study was conducted from both theoretical and experimental standpoints, utilizing ab initio calculations at the HF/6-31G+ level to understand the cyclization process. The researchers generated phenoxide ions in situ under aprotic conditions through the desilylation of o-silyloxyphenyl ethynyl ketones with spray-dried potassium fluoride and 18-crown-6 in anhydrous DMF. This approach led to the smooth cyclization of various o-hydroxyphenyl ethynyl ketones, producing benzopyranone derivatives with high selectivity. The presence of a small amount of proton donor was found to be essential for the high 6-endo-digonal selectivity, and the study concluded that both 6-endo-digonal and 5-exo-digonal cyclizations are reversible in aprotic media, with the irreversible protonation of the resulting vinyl anion being critical for product formation.
10.1016/S0040-4020(01)96527-5
The study investigates the Wittig, Wittig-Horner, and Knoevenagel reactions in the presence of alumina or potassium fluoride supported on alumina, without using organic solvents. The chemicals involved include phosphonium salts, which act as reactants to form ylides in the Wittig reaction, and phosphonates that participate in the Wittig-Horner reaction. Aldehydes and ketones serve as carbonyl compounds reacting with the ylides and phosphonates. Alumina and potassium fluoride supported on alumina function as catalysts and reaction media, with alumina selectively favoring the Knoevenagel reaction and potassium fluoride promoting the Wittig-Horner reaction. A small amount of water is found to increase the reaction rates of Wittig and Wittig-Horner reactions by solvating the catalyst surface and aiding in the formation of intermediates. The study demonstrates that these reactions can be effectively catalyzed without solvents, offering a more environmentally friendly approach to organic synthesis.
10.1021/acs.joc.9b02198
Avishek Guin, Rahul N. Gaykar, Subrata Bhattacharjee, and Akkattu T. Biju describe a non-transition metal synthetic method for the synthesis of N-H and N-arylbenzotriazoles via a [3+2] cyclization reaction of sodium azide (NaN3) with arynes. The study showed that the use of cesium fluoride (CsF) as a fluorine source in acetonitrile (CH3CN) solution resulted in the selective generation of N-H benzotriazoles, while the use of potassium fluoride (KF) in tetrahydrofuran (THF) solution under open flask conditions resulted in the generation of N-arylbenzotriazoles. The method was optimized to provide high selectivity and yields, with N-H benzotriazoles in 64% yield and N-arylbenzotriazoles in 94% yield. The researchers also explored substrate applicability and successfully synthesized a variety of benzotriazoles containing different arynes. Mechanistic experiments showed that the reaction first proceeded via a [3+2] cyclization reaction followed by an N-arylation reaction, with atmospheric moisture playing an important role in the protonation process.
T
