Microwave-Assisted Or Combined Microwave And Ultrasound-Assisted Multicomponent Reactions

The research described in this thesis aims to improve and develop new and more efficient approaches for the preparation of useful intermediate and candidate drug molecules, i.e. the propargylamines and five-or six-membered ring heterocycle compounds. The implemented synthetic strategy, based on multicomponent reactions (MCRs) under microwave or combined microwave and ultrasound irradiation, provides with its synthetic effciency, intrinsic atom economy, and procedural simplicity an elegant entry to aim the target compounds.Chapter 1 briefly explores the advances in and advantages of multicomponent reactions (MCRs) in contrast to traditional methods; also the application of microwave or/and ultrasound irradiation is discussed and microwave-assisted multicomponent reactions and combined microwave and ultrasound-assisted heterogeneous reaction in particular.Chapter 2 describes a new approach for the construction of polysubstituted propargyl-amines via a microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine and an alkyne (OA2-coulpling) in the presence of a catalytic amount of copper(I) catalyst.27 examples were generated in yields up to 95%Chapter 3 exploits the above acquired knowledge for the development of a novel tandem A3-coupling/decarboxylative coupling to form 3-amino-1,4-enynes. In addation, the currently acknowledged mechanistic aspects related to this relatively new transformation are dicussed.Chapter 4 discusses the discovery and elaboration of the Cu(I)-catalyzed decarboxylation of a propiolic acid for the synthesis of propargylamines. Attempts to expand the method to a cascade process for the formation of oxazolidin-2-ones are also described:Cu(I)-catalyzed tandem decarboxylative/carboxylative cyclization of a propiolic ccid, a primary amine and an aldehyde.Chapter 5 deals with an improved synthetic procedure for the synthesis of polysubstituted pyridines under combined microwave and ultrasound irradiation (CMUI):K2CO3-promoted tandem addition/cyclization/hydrogen shift process. The reaction can be completed in few minute and 71-90% yields of pyridines were obtained.Chapter 6 focuses on the use of CMUI technology for the construction of substituted 1,3,4-thiadiazoles in aqueous media by two different methods. Suitable substrates have been screened to construct multifunctional and complex target molecules:5-aryl-1,3,4-thiadiazol -2-amine, N-arylidene-5-aryl-1,3,4-thiadiazole-2-amines, N-phenyl-5-aryl-1,3,4-thiadiazole-2-amines.