OPTICALLY ACTIVE PHOSPHINE OXIDES. 15.¹ STEREOCHEMISTRY AND X-RAY STRUCTURE OF THE MAJOR CYCLOADDUCT DERIVED FROM THE RACEMIC 2,3-DIHYDRO-1-PHENYL-1H-PHOSPHOLE 1-OXIDE AND A HOMOCHIRAL NITRONE

Abstract

The structure and absolute configuration of homochiral 2-benzyl-3-(2,2-dimethyl-1,3-dioxolan-4-yl)-4-phenylhexahydro-4H-phospholo-[2,3-d]isoxazole 4-oxide obtained in predominance from racemic 2,3-dihydro-1-phenyl-1H-phosphole 1-oxide and D-glyceraldehyde derived nitrone in the process of kinetic resolution was analyzed by a single-crystal X-ray diffraction technique. C₂₃H₂₈NO₄P, monoclinic, space group P2₁, a = 5.7646(4) Å, b = 8.7280(4) Å, c = 21.3417(9) Å, β = 92.828(5)°, V = 1072.464(5) ų, Z = 2. The structure was solved by direct methods and was refined by full matrix least-squares calculations to R = 0.034 and R_w = 0.041 using 2282 unique reflections with I > 3σ(I). The absolute configuration was determined by Hamilton method and was found to be 3S, 3aS, 4R, 6aS, 4′S. All the three five-membered rings in the studied molecule assumed a deformed envelope conformation and the planes of the two fused rings are found to form a dihedral angle of 59.3(1)°. One intramolecular and one intermolecular short contacts of the C—H…O nature were revealed.

Key Words:

• Phospholene oxide
• 1,3-dipolar cycloaddition
• enantiomeric C—P heterocycle
• absolute configuration
• X-ray analysis
• C—H…O short contacts