Lewis Acid Catalyzed Organic Reactions In Organic Synthesis

Lewis acid complexes are essential instruments in the toolbox of organic chemists, which have gained an extensively attention in recent years. The use of Lewis acid as a kind of catalysts and efficient processes that are now able to compete to other transition metal-catalyzed ones have emerged in the carbon-carbon and carbon-heteroatom bond formation, C-H bond activation, and hydrogenation areas. The current requirements for efficient, selective and environmentally friendly reagent have increased the demand for such metal-based reaction promoters, especially the ones that can be applied in catalytic amounts. In contrast to other Lewis acids, which often are required in stoichiometric quantities and toxic, the use of iron and its salts as catalysts in synthetic chemistry readily promote a range of reactions in catalytic quantities and have the potential to form valuable carbon-carbon bonds and achieve functional groups transformation from simple starting materials. This results encourged us to focus our attention on the use of iron catalysts in organic synthesis. Herein, we reports FeCl3 catalyzed condensation reaction of 2-naphthol and aldehyde under solvent-free condition and Iron-catalyzed regio- and stereoselective addition of acid chlorides to alkynes, and we also achieved indium-catalyzd system for the formation of benzoxazoles from acyl chlorides and 2-aminophenols.The main works were summarized as follow:(1)An iron-catalyzed condensation of 2-naphthol with aldehydes has been described. In the presence of a catalytic amount of iron(III) chloride (5 mol%), the condensation reaction of 2-naphthol and aldehydes underwent smoothly to generate the corresponding products in good to excellent yields under base-, acid-, ligand-, additive-, and solvent-free reaction conditions.(2)An iron-catalyzed regio- and stereoselective addition of acid chlorides to alkynes has been described. The reaction utilizes an inexpensive iron catalyst system and it is suitable for the formation of a variety of bifunctional molecules. This is an inexpensive, regio-, stereoselective and atom-economical approach toβ-chloro-α,β-unsaturated ketones from simple and readily available starting materials.(3)Benzoxazole derivatives have been prepared through the reaction of substituted 2-aminophenols and acyl chlorides in the presence of catalytic amount of In(OTf)3 under solvent-free reaction conditions in good to excellent yields. The method is simple, convenient, environmental-friendly, efficient and practical.