Cascade Phosphorylation/Cyclization of Propargylic Alcohols with R ₂ P(O)–H: Access to Diverse 6-Phosphoryl-6-vinyl Indeno[2,1- b ]indoles

A novel cascade phosphorylation/cyclization of indole-containing propargylic alcohols with P(O)-H species under mild conditions is described. This strategy provides an efficient and practical approach to obtaining various valuable 6-phosphoryl-6-vinyl indeno[2,1-b]indoles via the construction of one C-P bond and one C-C bond in a single procedure. This reaction proceeded via a phosphorylated allene initiating the subsequent highly regioselective 5-exo-trig cyclization to afford the target products, which first demonstrates the cyclization as a new reaction mode compared with conventional cyclization pathways.