Direct Synthesis of Benzo[ b ]fluorenyl Thiophosphates via Tandem Cyclization of Diynols with (RO) 2 P(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) 2 P(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) 2 P(O)SH acted not only as a nucleophile but also as an acid-promoter to initiate the reaction.