VERBINDUNGEN MIT DEM 1,3,2-DIOXAPHOSPHORINAN-GRUNDGERÜST: SYNTHESE UND KONFORMATIONSANALYSE VON 2-R-2-OXO-5-BROM-5-NITRO-1,3,2-DIOXAPHOSPHORINAN-DERIVATEN

Abstract

2-Methyl- and 2-chloro-5-nitro-1,3,2-dioxaphosphorinane derivatives 1 and 2 have been prepared by the reaction of 5-nitro-1,3-propanediol with methyldichlorophosphine and phosphorus trichloride. The hydrolysis of 2 and the reaction with ethanol furnished the products 3 and 4. 2-methoxy- and 2-methyl-2-oxo-5-nitro-1,3,2-dioxaphosphorinane derivatives 5 and 6 were prepared by the oxidation of 1 and 3 with NO₂ or (Me₃Si)₂O₂, respectively or by the reaction of 3 and 4 with CH₃J. The reaction of 5 and 6 with sodium hydroxide, followed by the bromination with Br₂, or methylation with CH₃J, furnished the dioxaphosphorinanes 7–9. The chair configuration at the phosphorus atom of the above compounds was established by NMR and IR spectral analysis. The δ (P) values for the equatorial P[dbnd]O group (4–9) a were found to be at higher frequency than those for the axial P[dbnd]O (4–9) b. ³¹P NMR data indicated that the chemical shifts of a isomers are generally upfield, compared to those of b analogues. Coupling constants between ring protons and between phosphorus and ring protons have been found to be valuable in assigning the stereochemistry at phosphorus.

Key Words:

• dioxaphosphorinane-2-methyl-5-nitro-
• 2-oxo-2-methyl-5-bromo-5-nitro-
• 2-oxo-2,5-dimethyl-5-nitro-
• 2-oxo-2-methoxy-5-bromo-5-nitro-
• oxidation of 1,3,2-dioxophosphorinane
• conformational equilibria