Reduction of 2-hydroxy-3-arylmorpholines to 3-aryl morpholines
2020
Wright, Stephen W. | Simpson, Brittany | Chinigo, Gary | Perry, Matthew A. | Maguire, Robert J.
2-Hydroxy-3-aryl morpholines are readily prepared from arylboronic acids, aqueous glyoxal, and 1,2-aminoethanols by a variant of the Petasis borono-Mannich reaction. We now show that the 2-hydroxy-3-aryl morpholines may be deoxygenated to 3-aryl morpholines by treatment with methanesulfonic anhydride and triethylamine to afford intermediate 3,4-dihydro-2H-1,4-oxazines, followed by reaction with a triacetoxyborohydride salt and acetic acid to afford 3-aryl morpholines. This reaction sequence constitutes a three step, “two pot” preparation of 3-aryl morpholines from readily available starting materials (1,2-aminoethanols, arylboronic acids, and glyoxal) with excellent functional group tolerance and adaptability to scale.
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