Carbon-Phosphorus Heterocycles. Synthesis and Conformational Analysis of Alkyl-Substituted 1,2,6-Triphenyl-4-phosphorinanones and Derivates

Article abstract of DOI:10.1021/jo00319a024

A series of substituted phosphorinanones has been prepared, and a conformational analysis has been performed on all of the systems via 1H, 13C, and 31 P NMR techniques.All of the compounds appear to be chair forms in solution as evidenced by the chemical shifts and coupling constants. 1,2,6-Triphenyl-3-methyl-4-phosphorinanone (1a') was obtained via a condensation of bis(hydroxymethyl)phenylphosphine and 1,5-diphenyl-2-methyl-1,4-pentadien-3-one in boiling pyridine.Only 1a' could be isolated from the reaction under these conditions.Oxidation and sulfurization afforded the corresponding oxide and sulfide which also were biased in solution at room temperature. 1,2,6-Triphenyl-3,5-dimethyl-4-phosphorinanone (1d') was prepared in similar fashion by using 1,5-diphenyl-2,4-dimethyl-1,4-pentadien-3-one under the same conditions as cited previously.This phosphine, 1d', was the lone product via NMR examination of the mixture and was also biased, as were the corresponding oxide and sulfide obtained by the methods cited above.Deuteration of the 3,5-positions in 1a' removed the H-H vicinal couplings in these systems and permitted structure diagnosis with respect to assigning the C-CH3 bonds as being equatorial.Moreover, the C(2)-C6H5 bond and the C(6)-C6H5 bond were established as of the equatorial type not only in 1a' but in all derivates thereof.However, in 1d' and its oxide and sulfide, the C(2)-C6H6 bond was axial. 13C NMR shifts and J_PC couplings for all of the compounds were correlated where possible with related data from 1r,cis-2(a),trans-6(e)-triphenyl-4-phosphorinanone 1-sulfide, the structure of which was established by X-ray diffraction work in the previous paper.Relaxation measurements (T₁ values) were employed where possible to make 13C NMR assignments as well.Amino-substituted derivates were obtained for 1,2,6-triphenyl-3-methyl-4-phosphorinanone and characterized.Oximation of the same phosphine did not result in oxidation of the phosphorus atom apparently because of steric hindrance, although oxidation had been reported in simple phosphorinanones.These highly substituted phosphorinanones are the first recorded, along with their 13C NMR spectral properties.