84185-00-2Relevant academic research and scientific papers
Three-membered Ring Heterocycles, 14. α-Halogenation of Tertiary Phosphane Oxides
Heuschmann, Manfred,Quast, Helmut
, p. 3384 - 3401 (2007/10/02)
The symmetrically substituted tertiary phosphane oxides 5 were obtained from phosphorus halides 4 and 6 using organometallic reagents.Dibenzylphenylphosphane oxide (5c) reacted with bromine at 150 deg C to give all three possible diastereomeric α,α'-dibromophosphane oxides. e.g. (R,R/S,S)-2c, (r)-2c, and (s)-2c, and one α-bromophosphane oxide 8.The phosphane oxides 5a, b, d were lithiated once or twice in the α-positions by means of butyllithium.The α,α'-dilithiophoasphane oxides -5 reacted with tetrachloromethane below -80 deg C to yield the α-chlorophosphane oxides 1c - e whose diastereomeric ratios were controlled kinetically.The thermodynamically controlled ratios were adjusted with bases.While the α-lithiated dineopentyl phosphane oxides -5a and -5d also afforded the α-chlorophosphane oxides 1c and 1d, respectively, with an excess of tetrachloromethane, the α,α-dichlorophosphane oxide 9 was formed from the α-lithiobenzylphosphane oxide 5b.This difference is attributed to the acidity of the α-protons and steric factors.The configurations and preferred conformations of the α,α'-dibromophosphane oxides 2c and the α-chlorophosphane oxides 1c - e were determined on the basis of the 1H-31P coupling of the methine protons.
