PPh _<b>3</b> -Promoted Sulfa-Michael Addition-Driven Cyclization: A Divergent Route to Access Spirothiochromanone Derivatives

A novel triphenylphosphine-mediated sulfa-Michael addition-triggered cascade reaction has been developed for the efficient synthesis of spirothiochromanone derivatives using 3<i>H</i>-benzo[<i>c</i>][1,2]dithiol-3-one as a sulfur surrogate. This transformation initiates with reductive S-S bond cleavage, smoothly delivering a diverse array of spiro-1,3-dimethylbarbiturate-thiochromanones and spiro-1,3-indanedione-thiochromanones under mild conditions. The current synthetic route features key advantages including operational simplicity, scalability, and excellent functional group compatibility with good to excellent conversions across substrates. Furthermore, this protocol obviates purification techniques such as column chromatography for the isolation of spiro-adducts, making it a valuable strategy for the construction of complex sulfur-containing spirocyclic scaffolds.