A short review: Chemistry of thioisatin and its derivatives

In recent years, the thioisatin (benzo[b]thiophene-2,3-diones) have attracted considerable attention due to their ability to act as intermediates in the preparation of a series of fused spiroheterocycles. The benzothiophenic frameworks are important targets in synthetic and medicinal chemistry because this fragment is a key moiety in a wide number of natural and synthetic agents. Subsequently the present study deals with the synthesis of a variety of spiroheterocycles for which different strategies have been evolved viz. [4+2] photocycloaddition (spiropyrans), cyclocondensation (benzodiazocine), nucleophilic cyclization (spirothioazolidinones) and air oxidation (disulfides). semicarbazide reacts with thioisatin at 3‑position (thiosemicarbazones, 2-hydroxy-(2 H )-3,3-diaryl- and 3-hydroxy-3 H -2,2-diaryl-benzo[b]thiophenes hydroxyl compounds), 4,9-dimethylthiophanthrenes.