10.1016/j.tet.2015.05.029
The study presents a novel and environmentally friendly heterogeneous catalytic process for the synthesis of 2,3-unsubstituted benzo[b]furans, which are significant structural motifs found in natural products and biologically active molecules. The researchers utilized tin-exchanged H-b zeolite (Sn-b) as a catalyst for the intramolecular cyclization of 2-aryloxyacetaldehyde acetals, achieving good to excellent yields of a wide range of functionalized 2,3-unsubstituted benzo[b]furans. The Sn-b zeolite demonstrated excellent shape selectivity, preferentially forming 6-substituted isomers with up to 97% regioselectivity. It could be easily recovered and reused without significant loss of activity. The study's findings offer an efficient and sustainable method for the production of various benzo[b]furan derivatives, addressing the need for an improved catalyst system over traditional acidic reagents like polyphosphoric acid (PPA) and Amberlyst-15, which have limitations in terms of safety, workup procedure, and mechanical strength.
10.1016/j.tetasy.2008.01.031
The research focuses on the chemoenzymatic preparation of enantiopure LL-benzofuranyl- and LL-benzo[b]thiophenyl alanines, which are important components in biological and pharmaceutical products. The study combines lipase-mediated dynamic kinetic resolution (DKR) with chemical and enzymatic hydrolytic steps to synthesize the enantiopure amino acids. The experiments involve the use of various commercially available starting materials, such as benzofuran, benzo[b]thiophene, and 1-(2-hydroxyphenyl)ethanone, which are transformed through a series of chemical reactions, including formylation, chloromethylation, and cyclisation, to produce the desired aldehydes and subsequently the racemic amino acids and their derivatives. The enzymatic DKR is then carried out using Novozyme 435 in different alcohols and solvents to achieve high enantioselectivity. The stereoselectivity and conditions of DKR are investigated, and the enantiomeric excess (ee) is determined using HPLC analyses with chiral columns. The research also includes the use of Acylase I for the kinetic resolution of racemic 2-acetamido-3-(heteroaryl)propanoic acids, leading to the final enantiopure products. The analyses used in this study include NMR spectroscopy, mass spectrometry, HPLC, and specific rotation measurements to confirm the configuration and purity of the synthesized amino acids.
10.1055/s-2001-16052
The research focuses on the regioselective synthesis of 2,3-disubstituted and 2,3,5-trisubstituted benzofurans, which are structural motifs found in many biologically active compounds, through Pd-catalyzed cross-coupling reactions. The purpose of the study was to develop a method for the selective functionalization of benzofuran derivatives, particularly at the 2-position, and to apply this methodology to a short synthesis of eupomatenoid-15, a naturally occurring benzofuran. The researchers found that initial Pd-catalyzed cross-couplings preferentially occurred at the 2-position, and subsequent Pd- or Ni-catalyzed reactions at less reactive positions were possible. They also discovered that a halogen-metal exchange at low temperature was more selective than a Pd- or Ni-catalyzed process for differentiating between the 3- and 5-positions. Key chemicals used in the process included 2,3-dibromobenzofuran (1), 2,3,5-tribromobenzofuran (2), various alkynes, palladium and nickel catalysts, copper iodide, triethylamine, and tert-butyl lithium, among others. The study concluded with the successful synthesis of eupomatenoid-15, demonstrating the applicability of the developed methodology for the synthesis of 2,3,5-trisubstituted benzofurans.
10.1039/c3cc43937b
The research focuses on the enantioselective synthesis of benzofurans and benzoxazines, which are important structural motifs found in numerous biologically active compounds. The study employs a combination of olefin cross-metathesis and intramolecular oxo-Michael reaction, utilizing chiral phosphoric acid and Hoveyda–Grubbs II catalysts. The reactants include ortho-allylphenols and enones, which undergo a cascade reaction to yield benzofuran and benzoxazine derivatives with moderate to good yields and enantioselectivity. The experiments involved screening various chiral phosphoric acids and optimizing reaction conditions, such as solvent choice and catalyst concentrations. Analyses used to determine the yield and enantioselectivity of the products included high-performance liquid chromatography (HPLC) and X-ray crystallographic analysis for the determination of absolute configuration. The study successfully demonstrated the versatility of the method with a range of substituted phenols and enones, leading to the synthesis of various chiral benzofuran and benzoxazine derivatives.
10.1021/ol800051k
The research focuses on the development of a mild and general method for the synthesis of benzofuran derivatives, which are prevalent in many biologically active compounds. The researchers utilized a cycloaddition reaction between arynes and iodonium ylides in the presence of cesium fluoride (CsF) as a catalyst, which allowed for the reaction of ortho-silyl aryltriflates with iodonium ylides at room temperature, yielding benzofurans in moderate to good yields. The study involved screening optimal reaction conditions using various bases and solvents, with CsF in acetonitrile proving to be the most effective. The experiments were conducted under an argon atmosphere, and the reactions were monitored using thin-layer chromatography (TLC) and gas chromatography (GC) analysis. The products were purified through extraction with diethyl ether, drying over anhydrous Na2SO4, and flash column chromatography. The structures of the synthesized benzofurans were confirmed using 1H and 13C NMR spectroscopy. The research also proposed a working mechanism for the reaction and discussed the regioselectivity observed in the products, attributing it to the properties of the reactants such as steric and electronic effects.
10.1016/j.tetlet.2020.152809
The study focuses on the acid-promoted selective synthesis of trifluoromethylselenolated benzofurans using Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate (TsSeCF3) as a stable and easily prepared electrophilic trifluoromethylselenolating reagent. The researchers optimized the reaction conditions to achieve moderate to good yields of SeCF3-substituted benzofuran derivatives with excellent regioselectivity. They also realized a tandem cyclization/trifluoromethylselenolation procedure of 1-methoxy-2-(arylethynyl)benzenes using FeCl3 as the catalyst. The study highlights the importance of benzofuran scaffolds in biologically active molecules and the potential enhancement of their biological and medical properties by incorporating the SeCF3 group. The optimized conditions and the wide range of substrates tested demonstrate the practicality of this synthetic route for the trifluoromethylselenolation of electron-rich heterocyclic compounds, with potential applications in pharmaceutical and biochemical research.
10.1139/V08-091
The study investigates the synthesis of bis(benzofuranyl)methanes and 2-benzofuran-1-nitroalkanes catalyzed by Bi(OTf)3. Benzofuran and various aldehydes are the main reactants. In acetonitrile solvent, Bi(OTf)3 catalyzes the Friedel–Crafts alkylation reaction between benzofuran and aldehydes to produce bis(benzofuranyl)methanes with good yields. When nitromethane is used as the solvent, the reaction forms 2-benzofuran-1-nitroalkanes as the major products. The study explores different metal triflates as catalysts and finds Bi(OTf)3 to be particularly effective and environmentally benign. The influence of various factors such as solvent, reaction temperature, and the type of aldehyde on the reaction outcomes is examined. The proposed mechanisms for the formation of the products involve the attack of benzofuran on intermediates formed in the presence of Bi(OTf)3.
Xi, 
Xn
