Selective C2 and C3 phosphorylmethylation of indoles with a phosphorylmethyl dibenzothiophenium reagent

Abstract

A novel electrophilic phosphorylmethylating reagent, S-([diethoxyphosphoryl]methyl) dibenzothiophenium salt, has been successfully synthesized with readily available starting materials. This reagent is air- and moisture-tolerant and bench-stable. Interestingly, the reagent exhibited excellent selectivity for the formation of indole C(sp²)–CH₂PO(OEt)₂ bonds at position C2 with a photocatalyst and at position C3 with a copper catalyst. Moreover, the resulting compounds with CH₂PO(OEt)₂ could be easily converted into free phosphinic acid, providing a new pathway for preparing complex acid molecules.