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.