Stereocontrolled route to some optically active β-hydroxy phosphine oxides using the stereoselective addition of metallated phosphine oxides to proline-derived keto aminals
An asymmetric Horner-Wittig addition reaction with a chiral auxiliary attached to the electrophile is described. The key step is the addition of metallated phosphine oxides to Mukaiyama's proline-derived keto aminals (for which improved syntheses are described) and a detailed study of the factors affecting the stereoselectivity of these reactions is presented. In particular, by suitable choice of metallation conditions, complementary stereoselectivities are observed: reactions in THF with no additives are syn selective (Felkin non-chelation control) whereas reactions in toluene with added lithium bromide are anti selective (Cram chelation control).
O'Brien, Peter,Warren, Stuart
p. 2117 - 2127
(2007/10/03)
Stereocontrolled Synthesis of R or S Diphenylphosphinoyl Hydroxy Aldehydes and 1,2-Diols Using Bicyclic Aminals
Homochiral diphenylphosphinoyl hydroxy aldehydes 1 and 2 have been made by diastereoselective additions of metallated methyldiphenylphosphine oxides 10 to Mukaiyama's keto aminals 8 and 9.Reduction to diphenylphosphinoyl 1,2 diols 3 and 4 is also described.Sharpless asymmetric dihydroxylation provides an alternative route diphenylphosphinoyl 1,2 diols 3 and 4, the two approaches are compared.
O'Brien, Peter,Warren, Stuart
p. 2681 - 2684
(2007/10/02)
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