Catalytic Hydrogenation of 5, 6‐Dihydro‐4H‐1, 2‐oxazines Bearing a Functionalized Methylene Group at C‐3статья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 21 сентября 2017 г.
Аннотация:The catalytic hydrogenation of readily available methyl 2-(5,6-dihydro-4H-1,2-oxazin-3-yl)acetates 6 has been studied. Dihydrooxazines 6 without an alkoxy substituent at C-6 under mild hydrogenation conditions in methanol produce a dynamic mixture of enamines 7 and tetrahydro-2-furanamines 7′(α + β). These products can be transformed into 1,4-amino alcohols 8 under more robust hydrogenation conditions or into isomeric dihydrofurans 9 and 10 if the reduction is carried out in glacial acetic acid. Reduction of dihydrooxazines 6h,i, which possess an alkoxy substituent at C-6, under similar conditions affords pyrrolidine derivatives 12, 13 and 14. A general mechanistic scheme for the hydrogenation reaction that involves an initial N–O bond cleavage has been suggested.