10039-56-2

Unsaturated phosphorus compounds, such as phosphaalkenes and phosphaalkynes, show a versatile reactivity in cycloadditions. Although phosphaketenes (R-P=C=O) have been known for three decades, their chemistry has remained limited. Herein, we show that heteroatom-substituted phosphaketenes, R3E-P=C=O (E=Si, Sn), are building blocks for silyl- and stannyl-substituted five-membered heterocycles containing three phosphorous atoms. The structure of the heterocyclic anion depends on the nature of the tetrel atom involved. Although the silyl analogue [P3C 2(OSiR3)2]- is an aromatic 1,2,4-triphospholide, the stannyl compound [P(CO)2(PSnR 3)2]- is a 1,2,4-triphosphacyclopenta-3,5- dionate with a delocalized OCPCO fragment. Because of their anionic character, these compounds can easily be used as building blocks, for example, in the preparation of a silyl-functionalized hexaphosphaferrocene or the parent 1,2,4-triphosphacyclopenta-3,5-dionate [P(CO)2(PH)2] -. NMR spectroscopic investigations and computations have shown that the heterocycle-formation reactions presented herein are remarkably complex. Cycle time! The reaction of Na(OCP) with tetrelhalides, R3EX (E=Si, Sn), gives silyl- and stannyl-substituted five-membered heterocycles containing three phosphorous atoms. Phosphaketenes, R3E-P=C=O, are intermediates, which react with Na(OCP) as a P- transfer reagent to the final products (see scheme; Tf=triflucromethanesulfonyl).

The esterfication of hypophosphorous acid is followed by reaction with another molecule of alcohol under the action of a nickel catalyst to provide a green method for the preparation of H-phosphonate diesters. This method avoids the need for any stoichiometric chlorine unlike those based on phosphorous trichloride.