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Reductive transformations of 5,6‐dihydro‐4 H ‐1,2‐oxazines: Synthesis of 4‐hydroxy ketoximes, N ‐hydroxypyrrolidine derivatives, and other nitrogen‐containing compounds
Author(s) -
Hippeli Claudia,
Reißig HansUlrich
Publication year - 1990
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199019900190
Subject(s) - chemistry , oxazines , oxime , hydrogenolysis , beckmann rearrangement , substituent , amine gas treating , medicinal chemistry , catalysis , hydride , ethanol , organic chemistry , combinatorial chemistry , hydrogen
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.