The aza-Diels–Alder reactions of cyclopentadiene and cyclo-1,3-hexadiene with various substituted N-arylimines in the presence of Yb/Sc triflates as catalyst in MeCN at room temperature gave quinoline and phenanthridine derivatives in moderate to high yields. Some of the cycloaddition reactions were carried out in ionic liquid.

The goal of the present research was to determine the protective potential of five newly synthesized indenopyridine derivatives against N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) and 9-aminoacridine (9-AA) induced mutagenesis. MNNG sensitive Escherichia coli WP2uvrA and 9-AA sensitive Salmonella typhimurium TA1537 were chosen as the bacterial tester strains. All of the test compounds showed significant antimutagenic activity at various tested concentrations. The inhibition rates ranged from 25.6% (Compound 2 - 1 mM/plate) to 68.2% (Compound 1 - 2.5 mM/plate) for MNNG and from 25.7% (Compound 4 - 1 mM/plate) to 76.1% (Compound 3 - 2.5 mM/plate) for 9-AA genotoxicity. Moreover, the mutagenicity of the test compounds was investigated by using the same strains. None of the test compounds has mutagenic properties on the bacterial strains at the highest concentration of 2.5 mM. Thus, the findings of the present study give valuable clues to develop new strategies for chemical prevention from MNNG and 9-AA genotoxicity by using synthetic indenopyridine derivatives.

A rapid, efficient and environment-friendly protocol for the synthesis of naphthopyranes has been developed by one-pot condensation of 2-naphthol, various aromatic aldehydes and benzoylacetone or 1,3-diphenyl-1,3-propandione in the presence of Cu(OTf)₂ as catalyst under ultrasonic irradiation. The present approach offers the advantages of clean reaction, simple methodology, short reaction time, high yield and economic availability of the catalyst.