Synthesis and Optical Properties of Novel Spiro[chromo(2,3-c)-pyrazole-4,1′-isobenzofuran]-3′-one Compounds

A series of novel spiro[chromo(2,3-c)pyrazole-4,1'-isobenzofuran]-3'-one compounds were synthesized via Knoevenagel condensation and dehydration reaction of 2-(4-dibutylamino-2-hydroxybenzoyl)benzoic acid or 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoic acid with pyrazolones using acid as catalysts and dehydrants. The effects of the ratio of the substrates, catalyst, temperature and reaction time were examined. Their optical properties in different pH and solvent were investigated. It shows that 1-(4-chlorophenyl)-7-(diethylamino)-3-methyl-1H,3'H-spirotcluomene[2,3-c]pyrazole-4, 1'- isobenzofuran]-3'-one (1e) and 1-(4-chlorophenyl)-7-(dibutylamino )-3-methy 1-1H,3'H-spiro [chromene[2,3-c]pyrazole-4,1'-isobenzofuran]-3'-one (1j) have potential as pH indicators for strong acids and bases.