Investigations on benz­[1,2]­oxaphos­phinane derivatives

The structures of two compounds, 3-[1-(2-hydroxy­ethyl­amino)­ethyl­idene]-2-methoxy-3,4-di­hydro-1,2λ⁵-benz­oxa­phosphinane-2,4-dione, C₁₃H₁₆NO₅P, and 3-[1-(2-hydr­oxy-­ethyl­amino)­ethyl­idene]-2-methoxy-6-methyl-3,4-di­hydro-1,2λ⁵-benz­oxaphosphinane-2,4-dione, C₁₄H₁₈NO₅P, have been studied and compared. The oxophosphinane rings have a half-chair conformation and extra six- and five-membered rings are formed by intramolecular N—H...O hydrogen bonds. An intermolecular O—H...O hydrogen bond is also observed.