There has been developed an easy synthetic approach to spiro[dihydrofuran-2,3'-oxindoles] via a highly diastereoselective formal [4 + 1] cycloaddition reaction of [e]-fused 1H-pyrrole-2,3-diones with diazooxindoles. The described novel heterocyclic systems are heteroanalogues of antimicrobial and antibiofilm fungal metabolites. The developed reaction represents the first example of involving 1H-pyrrole-2,3-diones fused at the [e]-side in a [4 + 1] annulation reaction.

An efficient and easy approach to the synthesis of novel racemic planar-chiral 3,4-dihydroferroceno[c]pyridines and 1H-ferroceno[c]pyrroles via the intramolecular Ritter reaction of 2-ferrocenyl-3,3-dimethylbutan-2-ol with nitriles and thiocyanates in the presence of MeSO₃H was developed. Aromatic and aliphatic nitriles, phenylacetonitriles, and β-oxonitriles produced exclusively 3,4-dihydroferroceno[c]pyridines. The condensation of 2-ferrocenyl-3,3-dimethylbutan-2-ol with various thiocyanates, including alkyl thiocyanates, benzyl thiocyanate, and ethyl 2-thiocyanatoacetate, yielded not only 3,4-dihydroferroceno[c]pyridines but also 1H-ferroceno[c]pyrroles. The selectivity of these reactions depended on the temperature and the order of addition. The size of substituents at the α-position to the sulfur atom of thiocyanates also had a significant effect on the distribution of products.

4-Aryl-2,4-dioxobutanoic acids react with 3-nitro- and 4-nitrobenzohydrazides in a 1 : 2 ratio to form the corresponding 3-aryl-1-(3-nitrobenzoyl)-5-[2-(3-nitrobenzoyl)hydrazinyl]-4,5-dihydro-1H-pyrazole-5-carboxylic acids and 3-aryl-1-(4-nitrobenzoyl)-5-[2-(4-nitrobenzoyl)hydrazinyl]-4,5-dihydro-1H-pyrazole-5-carboxylic acids. The structure of the products was confirmed by X-ray diffraction analysis. The reaction proceeds under mild, catalyst-free conditions to give high yields, and the products were isolated without column chromatography. The synthesized compounds exhibit potential for diverse biological activities.

A new approach for the efficient and convenient synthesis of novel aminoalkyl-functionalized 4-arylquinolines via the Friedländer reaction of differently substituted 2-(3,4-dihydroisoquinolin-1-yl)anilines with various α-methylene ketones in acetic acid was developed. The reaction allows easy access to a diversity of 4-arylquinoline derivatives in moderate to excellent yields under mild conditions.