Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1-3 with the Knoevenagel adducts 4-6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13-17), under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts....

Diazophosphonates, readily prepared from α-ketophosphonates by oxidation of the corresponding hydrazones in batch or flow, are useful partners 1,3-dipolar cycloaddition reactions to alkynes give N-H pyrazoles, including first intramolecular examples such a process. The phosphoryl group imbues number desirable properties into diazo 1,3-dipole. electron-withdrawing nature stabilizes compound maki...

The thermal [4+2] cycloadditions of 3-acetyl-, 3-carbamoyl, and 3-ethoxycarbonylcoumarins with 2,3-dimethyl-1,3-butadiene under solvent free conditions are reported, as well as the epoxidation reactions of some adducts. Discussion is focused on the structural features of the Diels-Alder adducts and their epoxides, based upon NMR, X-ray, and mass spectral data, and supported by ab initio theoret...

This review highlights the biological importance of many polysubstituted nitro-prolines and -pyrrolidines. Their preparation using asymmetric 1,3-dipolar cycloadditions of azomethine ylides with nitroalkenes using diastereoselective and enantioselective strategies is described remarking the scope and main features of each one.

Ni(ClO(4))(2)·6H(2)O-catalysed regioselective and diastereoselective [3+2]-annulations of aryl oxiranyl-dicarboxylates and indoles via selective C-C bond cleavage of oxirane were revealed. The cycloadditions proceed smoothly with high regio- and diastereoselectivity under mild conditions leading to 1H-furo[3,4-b]indoles in good to excellent yields.

A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and a second achiral thiourea. Experimental evidence points to a new type of cooperative catalysis with each species being necessary to generate a reactive pyrylium ion pair that undergoe...

Neutral, C2-symmetric S/C/S ligands based on N-heterocyclic carbenes and thioether functionalities were incorporated into transition metal complexes characterised by two direct metal-stereogenic sulfur bonds. This new ligand design was applied to 1,3-dipolar cycloadditions as the first example of the use silver of carbenes in asymmetric catalysis.