X-RAY CRYSTAL STRUCTURES OF Cis- AND Trans-3-(DIPHENYLHYDROXYMETHYL)-2-ETHOXY-2-OXO-1,2-OXAPHOSPHORINANES AND AN ASSOCIATED STUDY OF HYDROGEN BONDING

Abstract

The molecular structures of both the cis(4a) and trans(4b) isomers of 3-(diphenylhydroxymethyl)-2-ethoxy-2-oxo-1,2-oxaphosphorinane were determined by the single crystal X-ray diffraction method. The cis and trans designation refer to the relative spacial arrangements of the phosphoryl oxygen and the substituent group on the α-carbon. The crystallographic data are for 4a: C₁₉H₂₃O₄P, M_r = 346.36 monoclinic, P2₁/c, a = 13.2774(9) Å, b = 8.5543(9) Å, c = 16.7289(25) Å, β = 111.142(10)°, V = 1772.2(4) ų, Z = 4, D_calc = 1.298 g cm⁻³, λ(MoKα) = 0.71069 Å, μ = 1.70 cm⁻¹, F(000) = 736, T = 298 K, R = 0.065 for 2099 reflections; and for 4b: C₁₉H₂₃O₄P, M_r = 346.36, monoclinic, P2₁/c, a = 9.5120(15) Å, b = 12.317(4) Å, c = 15.309(3) Å, β = 100.717(15)°, V = 1762.3(7) ų, Z = 4, D_calc = 1.305 g cm⁻³, μ(MoKα) = 0.71069 Å, μ = 1.60 cm⁻¹, F(000) = 736, T = 298 K, R = 0.041 for 1638 reflections. In both structures the diphenylhydroxymethyl group is in an equatorial position, and the 1,2-oxaphosphorinane ring adopts a chair conformation. In the solid state 4b (trans) shows neither inter- or intramolecular hydrogen-bonding, while 4a (cis) exhibits intramolecular H-bonding of the type O—H···O[dbnd]P. The chair conformation of 4a is flattened at the C4 end relative to the conformation of 4b. Solution IR spectroscopy studies of υ(OH) reveal that only one conformer of 4a is observed which is assignable to the rotamer containing the intramolecular hydrogen bond.

Key Words:

• X-ray crystal structure
• oxaphosphorinane
• phostone
• intramolecular
• hydrogen bonding