# Novel Metal-Free Synthesis of 3-Substituted Isocoumarins and Evaluation of Their Fluorescence Properties for Potential Applications

## TL;DR

A new metal-free method to make 3-substituted isocoumarins is developed, showing good yields and potential for fluorescent materials.

## Contribution

A novel metal-free synthesis of 3-substituted isocoumarins with high yields and functional group tolerance is introduced.

## Key findings

- The synthesis achieved excellent yields (up to 90%) with high functional group tolerance.
- Isocoumarin derivatives showed good photoluminescence in THF with a large Stokes shift.
- The absolute fluorescence quantum yield reached up to 14%.

## Abstract

A novel metal-free synthesis of 3-substituted isocoumarins through a sequential O-acylation/Wittig reaction has been established. The readily accessible (2-carboxybenzyl)-triphenylphosphonium bromide and diverse chlorides produced various 1H-isochromen-1-one in the presence of triethylamine, employing sequential O-acylation and an intramolecular Wittig reaction of acid anhydride. Reactions using these facile conditions have exhibited high functional group tolerance and excellent yields (up to 90%). Moreover, the fluorescence properties of isocoumarin derivatives were evaluated at the theoretical and experimental levels to determine their potential application in fluorescent materials. These derivatives have good photoluminescence in THF with a large Stokes shift and an absolute fluorescence quantum yield of up to 14%.