Microwave-Assisted Cerium(III)-Promoted Cyclization of Propargyl Amides to Polysubstituted Oxazole Derivatives

Lewis Acid-Promoted Three-Component Cyclization for the Construction of Functionalized Oxazoles

A simple and efficient synthetic strategy from amides, ynals, and sodium sulfinates via a Lewis acid-promoted three-component reaction has been reported. Thus, a broad range of various aryl (not alkyl)-substituted oxazoles could be synthesized via the formation of C-N, C-O, and C-S bonds in a one-pot process. In addition, this reaction possesses other unique advantages, such as transition metal-free catalysis, high step economy, good functional group tolerance, and good regioselectivity.

Chemo- and Stereoselective Synthesis of Substituted Thiazoles from tert-Alcohols Bearing Alkene and Alkyne Groups with Alkaline Earth Catalysts

We report here that thioamides can distinguish C-C double bonds and C-C triple bonds chemoselectively when subjected to a reaction with pent-1-en-4-yn-3-ol derivatives in the presence of Ca(OTf)₂. This protocol offers a fast, efficient, and high-yielding synthesis of functionalized thiazoles. Interestingly, this reaction offers a time-dependent formation of kinetic and thermodynamic products. The products showed stereoselectivity concerning the alkene geometry. Further, we extended this protocol to synthesize oxazoles from propargyl alcohols and ibuprofen (NSAID) was converted into amide and then subjected to oxazole formation with tert-propargyl alcohols.

Cu(I)-Catalyzed Three-Component Cyclization for the Construction of Functionalized Thiazoles

A novel and straightforward strategy for the synthesis of functionalized thiazoles from thioamides, ynals, and alcohols via a copper(I)-catalyzed three-component reaction has been described. Through the formation of new C-S, C-N, and C-O bonds in one pot, it is easy to produce various valuable thiazoles fixed with aryl or heteroaryl groups. In addition, the reaction also exhibits other unique advantages, such as high step economics, good functional group tolerance, and good regioselectivity.

Synthesis and Reactivity of Propargylamines in Organic Chemistry

Propargylamines are a versatile class of compounds which find broad application in many fields of chemistry. This review aims to describe the different strategies developed so far for the synthesis of propargylamines and their derivatives as well as to highlight their reactivity and use as building blocks in the synthesis of chemically relevant organic compounds. In the first part of the review, the different synthetic approaches to synthesize propargylamines, such as A³ couplings and C-H functionalization of alkynes, have been described and organized on the basis of the catalysts employed in the syntheses. Both racemic and enantioselective approaches have been reported. In the second part, an overview of the transformations of propargylamines into heterocyclic compounds such as pyrroles, pyridines, thiazoles, and oxazoles, as well as other relevant organic derivatives, is presented.

Readily switchable one-pot 5-exo-dig cyclization using a palladium catalyst

A convenient, ligand-free, Pd(OAc)₂-catalyzed one-pot reaction has been developed for the synthesis of oxazolines and oxazoles from easily available acid chlorides and propargylamine.

Transition-metal-free synthesis of oxazoles: valuable structural fragments in drug discovery

This review article encapsulates the recent developments in the metal-free approaches used to construct oxazole moiety.

Iodine-promoted cyclization of N-propynyl amides and N-allyl amides via sulfonylation and sulfenylation

Metal-free synthesis via endo carbon functionalization of N-propynyl/allyl amides with sulfonyl hydrazides to afford sulfonylated oxazoles and sulfenylated oxazolines.

An efficient one-pot two catalyst system in the construction of 2-substituted benzimidazoles: synthesis of benzimidazo[1,2-c]quinazolines

The benzimidazole core is a common moiety in a large number of natural products and pharmacologically active small molecules. The synthesis of novel benzimidazole derivatives remains a main focus in medicinal research. In continuation of the efforts towards Ce(III) catalysts for organic transformations, we observed for the first time the activity of the iodide ion and copper cation in activating CeCl3·7H2O in the selective formation of prototypical 2-substituted benzimidazoles. The one-pot CeCl3·7H2O-CuI catalytic system procedure includes the cyclo-dehydrogenation of aniline Schiff's bases, generated in situ from the condensation of 1,2-phenylenediamine and aldehydes, followed by the oxidation with iodine, which works as a hydrogen sponge. Mild reaction conditions, good to excellent yields, and clean reactions make the procedure a useful contribution to the synthesis of biologically active fused heterocycles containing benzimidazoquinazolines.

Construction of heterocyclic structures by trivalent cerium salts promoted bond forming reactions

Cerium(III) salts have recently gained increasing attention in the synthetic community, owing to the powerful features that are reviewed in detail in this tutorial. This review reports significant examples of cerium(III) promoted synthesis of heterocyclic structures, initially dealing with the synthesis of five- and six-membered ring nitrogen containing heterocycles, then describing the preparation of their oxygenated analogues and finally discussing the achievement of seven-membered rings and mixed heterocyclic motifs.

CuI-catalyzed cycloisomerization of propargyl amides

The synthesis of substituted dihydrooxazoles by the CuI-catalyzed cycloisomerization of terminal propargyl amides is reported.