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Reductive transformations of 5,6-dihydro-4H-1,2-oxazines: Synthesis of 4-hydroxy ketoximes,N-hydroxypyrrolidine derivatives, and other nitrogen-containing compounds

✍ Scribed by Hippeli, Claudia ;Reißig, Hans-Ulrich

Publisher
John Wiley and Sons
Year
1990
Tongue
English
Weight
566 KB
Volume
1990
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

6‐Siloxy‐substituted 1,2‐oxazines 1 are transformed into 4‐hydroxy ketoximes 2 by reduction with NaBH~4~ in ethanol. Reductive Beckmann rearrangement converts the oxime 2a into the 1,4‐amino alcohol 7. Diisobutylaluminum hydride (DIBAH) induces a novel reductive ring contraction of 1 to provide either N‐hydroxypyrrolidine derivatives 8 or nitrones 9. Other 1,2‐oxazines lacking the 6‐siloxy substituent are also studied under these reaction conditions. Catalytic hydrogenolysis either gives the acyclic amine 16 or it stops at the stage of the proline derivative 21. Mechanistic features of these synthetically valuable transformations are discussed.

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