Highly Atom-Economic, Catalyst-Free, and Solvent-Free Synthesis of Phthalazinones

Herein a simple, catalyst- and solvent-free system for highly atom-economic synthesis of phthalazinones has been developed using phthalaldehydic acid, 2-acyl-benzoic acid, and substituted hydrazine as simple substrates. The reaction time was shortened to 20–60 min. Structurally diverse phthalaldehydic acids, 2-acyl-benzoic acids, and hydrazines were transformed into phthalazinones with a nearly 100% yield regardless of the aggregate state and electronic nature of the substituents. The transformation was demonstrated to be amenable for scale-up with multiple liquid and solid materials. In addition, isolation and purification of the crude products can be simply done with only crystallization. The heavy metal pollution was also eliminated from the source.