Direct Synthesis of Benzo[b]fluorenyl Thiophosphates via Tandem Cyclization of Diynols with (RO)2P(O)SH

A general and metal-free protocol for the construction of benzo­[b]­fluorenyl thiophosphates was developed through the cascade cyclization of easily prepared diynols and (RO)2P­(O)­SH, with water as the only byproduct. The novel transformation involved the allenyl thiophosphate as the key intermediate, followed by Schmittel-type cyclization to achieve the desired products. Notably, (RO)2P­(O)­SH acted not only as a nucleophile but also as an acid-promoter to initiate the reaction.