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Stereoselective synthesis of (1R)- and (1R,2S)-1-aryl-2-alkylamino alcohols from (R)-cyanohydrins

✍ Scribed by Franz Effenberger; Beate Gutterer; Jürgen Jäger

Publisher
Elsevier Science
Year
1997
Tongue
English
Weight
595 KB
Volume
8
Category
Article
ISSN
0957-4166

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✦ Synopsis

Hydrogenation of (R)-cyanohydrins (R)-I with LiAIH4 occurs without racemization to give the (R)-2-amino alcohols (R)-3. (1R,2S)-2-Amino alcohols (1R,2S)-4 are obtained with high diastereoselectivity by addition of methyl Grignard to Osilyl protected cyanohydrins (R)-2 and subsequent hydrogenation with NaBH 4. The Nalkylated 2-amino alcohols (R)-8 and (1R,2S)-9 can be prepared either by reductive alkylation of the corresponding 2-amino alcohols (R)-3 and (1R,2S)-4, respectively, or by a transimination reaction of the Grignard addition products with primary amines and subsequent hydrogenation with NaBH 4. The lower diastereoselectivity of hydrogenation in case of the N-alkylimino compounds in comparison to the N-unsubstituted imines is explained by a weaker chelating effect. (~) 1997 Elsevier Science Ltd. All rights reserved.

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