Condensation product of o-aminophenol and pyrrole-2-carboxylaldehyde behaves as a fluorescent sensor for Fe³⁺ and Sn²⁺ ions in aqueous medium over the other metal ions like Na⁺, K⁺, Mg²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Mn²⁺ and Cr³⁺. In aqueous solution, Fe³⁺ and Sn²⁺ ions coordinate to the receptor through a NON binding site which induces a strong fluorescence enhancement. Receptor can be applied as fluorescence enhanced probes for transition metal ions due to the inhibition of photo induced electron transfer (PET) mechanism.

An efficient, green, and facile four-component reaction for the preparation of pyrano[2,3-c]pyrazole derivatives through the condensation reaction of aryl aldehydes, ethyl acetoacetate, malononitrile, and hydrazine hydrate or phenyl hydrazine in the presence of commercially available organocatalyst sodium benzoate under aqueous condition is reported. The products are produced with high yields and in shorter reaction times. It also is mild, safe, green and environmental friendly.