CONFORMATIONS OF SATURATED SIX-MEMBERED-RING PHOSPHORUS HETEROCYCLES. SYNTHESES AND X-RAY CRYSTAL STRUCTURES OF THREE 2-ANILINO-2-OXO-5,5-DIMETHYL-1,3,2-OXAZAPHOSPHORINANES

Abstract

Abstract Single-crystal X-ray structural determinations have been made on 2-anilino-2-oxo-5,5-dimethyl-1,3,2-oxazaphosphorinane. 1; 2-(4-fluoroanilino)-2-oxo-5,5-dimethyl-1,3,2-oxazaphosphorinane. 2; and 2-(4-dimethylaminoanilino)-2-oxo-5,5-dimethyl-1,3,2-oxazaphosphorinane, 3. Compounds 1 and 2 are iso-structural and crystallize in the monoclinic space group P21/c with four molecules per unit cell. The cell dimensions for 1 are: a=12.234(4) Å, b=8.891(3) Å, c=12.152(4) Å, and B=110.77(4)°. The cell dimensions for 2 are: a=12.505(1) Å, b=8.919(1) Å, c=12.211(1) Å, and B=109.14(1)°. Compound 3 crystallizes in the monoclinic space group P21/c with four molecules per unit cell of dimensions a=6.321(2) Å, b=19.963(3) Å, c=12.236(2) Å, and B=104.89(4)°. Full-matrix least-squares refinement for each of the structures led to conventional R factors of 5.1% for 1, 4.9% for 2, and 9.5% for 3. The conformation adopted by 1 and 2 is the chair conformation with the anilino substituent axial. Compound 3 adopts the alternative chair conformation with an equatorially disposed anilino substituent. Structural variations are found which can be attributed to the operation of exo and endo anomeric effects.