6191-36-2Relevant articles and documents
Stereoselective umpolung reactions with metalated p-chiral cyanohydrin phosphates-enantioselective synthesis of tertiary cyanohydrins
Schrader, Thomas
, p. 1273 - 1282 (2007/10/03)
We present the first cyanohydrin derivative 4 that allows diastereoselective umpolung reactions. In 4 the OH group of the cyanohydrin is linked with a chiral phosphate, which can be removed hydrolytically after asymmetric synthesis. Cyclization of pseudoephedrine 1d with POCl3 gave 2d. This was followed by addition of racemic benzaldehyde cyanohydrin 3 to give the key intermediate 4d. With complete retention of the configuration at phosphorus. Deprotonation of 4d, followed by addition of a wide variety of electrophiles afforded the crystalline products 5 with high diastereomeric excesses (de up to 94%). High asymmetric induction was also achieved for the reaction of 4-Li+ with acyl halides, α-bromoacetates, 2-cycloalkenones, α,β-unsaturated esters, and γ-bromoacetates. Lewis acid assisted hydrolysis proceeded without racemization and gave high yields of ketone cyanohydrins 6. From the ring-opened chiral auxiliary 7, optically pure pseudoephedrine 1 was readily recovered by acid hydrolysis. Optically pure (R) and (S) ketone cyanohydrins are now accessible in a very general strategy, which circumvents the substrate limitations of enzymatic synthesis.
Reactions of chiral β-ketosulfoxides with Et2AlCN: Asymmetric synthesis of cyanohydrin derivatives
Garcia Ruano,Martin Castro,Rodriguez
, p. 3195 - 3198 (2007/10/02)
The reaction of chiral p-tolylsulfinylmethyl ketones (R-CO-CH2-SOTol, R=Ph, Et and t-Bu) with Et2AlCN, yields almost optically pure sulfinyl cyanohydrins (d.e. ≥ 96%). The reaction was quicker in the presence of ZnCl2, but
