Crystal structure, protolytic properties and alkylating activity of 3-(1-amino-ethylidene)-2-methoxy-2-oxo-2,3-dihydro-2λ5-benzo[e][1,2]oxaphosphinin-4-one

The crystal structure of 3-(1-amino-ethylidene)-2-methoxy-2-oxo-2,3-dihydro-2λ5-benzo[e][1,2]oxaphosphinin-4-one (1a), protolytic properties and alkylating activity were determined. The title compound exists in solid state as a keto-amine form. Compound 1a behaves in 5% v/v 1,4-dioxane-water solution as a monofunctional molecule within pH 3.0-5.0. As determined in an in vitro Preussmann test compound 1a exhibits high (+++) alkylating activity. The crystal structure of the title compound has been determined by X-ray methods and NMR spectroscopy. The crystals are orthorhombic, space group P212121, with a=9.296(1), b=10.169(1), c=12.694(1) Å, V=1200.1(2) Å3, Z=4, Dc=1.401 g cm−3, F(000)=528, T=153 K ∝ (Mo Kα)=0.231 mm−1. The molecule adopts the keto-amine tautomeric form with medium strong N-H⋯O hydrogen bond. A characteristic motif of the crystal packing are 'zigzag' chains parallel to b axis.