89556-40-1Relevant articles and documents
A convenient one-pot synthesis of quaternary α-methoxy- and α- hydroxycarboxylic acids
Yabuuchi, Tetsuya,Kusumi, Takenori
, p. 684 - 686 (2007/10/03)
Several α-methoxy- and α-hydroxycarboxylic acids have been synthesized by a new one-pot synthesis using ketones, tribromomethane, and potassium hydroxide in methanol and water, respectively, in good yields.
A General Strategy to Enantiomerically Pure Aliphatic and Olefinic Ketone Cyanohydrins by Stereoselective Alkylation of Umpoled Aldehyde Derivatives
Kirsten, Christian N.,Herrn, Michael,Schrader, Thomas H.
, p. 6882 - 6887 (2007/10/03)
We present the first general synthesis of optically pure (R)- and (S)-ketone cyanohydrins with olefinic and aliphatic substituents. Consecutive condensations of POCl3 with pseudoephedrine (1) and racemic crotonaldehyde cyanohydrin (3, R = 1-propenyl) lead to the respective cyanohydrin phosphate 4c. Deprotonation, followed by highly stereoselective alkylation and a single Chromatographic purification step, afford diastereomerically pure ketone cyanohydrin phosphates 5a-e. From these, enantiomerically pure tertiary cyanohydrins 6a-e can be obtained by mild Lewis acid-assisted hydrolysis. Pseudoephedrine is simultaneously recovered without loss of optical purity. The unsaturated alkylation products 5a-d are readily hydrogenated with diimide to aliphatic cyanohydrin phosphates 5f- i, which can be cleaved to furnish the free optically pure cyanohydrins 6f-i. Thus a broad variety of both saturated and unsaturated ketone cyanohydrins with R > Et becomes accessible in optically pure form for the first time. The free cyanohydrins are easily converted to optically pure α-branched α-hydroxy acids.
Asymmetric Syntheses Based on 1,3-Oxathianes. 2. Synthesis of Chiral Tertiary α-Hydroxy Aldehydes, α-Hydroxy Acids, Glycols (RR'C(OH)CH2OH), and Carbinols (RR'C(OH)CH3) in High Enantiomeric Purity
Lynch, Joseph E.,Eliel, Ernest L.
, p. 2943 - 2948 (2007/10/02)
A chiral 1,3-oxathiane (5) prepared from (+)-pulegone in three steps is converted to diastereomerically pure equatorial 2-acyl derivatives by lithiation, condensation with aldehydes, and Me2SO oxidation.Reaction of the resulting ketones with Grignard reagents at -78 deg C again proceeds highly stereoselectively (diastereomer excess generally above 90percent) according to Cram's rule (cyclic model).The resulting tertiary carbinols when cleaved with NCS/AgNO3 give chiral tertiary α-hydroxy aldehydes, RR'C(OH)CHO, plus a mixture of epimeric sultines which may be readily reconverted to the starting oxathiane.The hydroxy aldehydes have been oxidized to chiral tertiary α-hydroxy acids, RR'C(OH)CO2H, and reduced to primary-tertiary glycols, RR'C(OH)CH2OH, and further to tertiary carbinols, RR'C(OH)CH3, all with over 90percent ee.The opposite enantiomers of these compounds (again >90percent ee) may be obtained by starting with a diastereomeric 1,3-oxathiane (6), also available from (+)-pulegone.The configurations of the chiral products may be deduced from the manner of preparation and the assumption that Cram's rule is valid and agree with prior assignments in the literature.
