Cu(OTf)2-catalysed synthesis of structurally novel bicyclic 1,3-oxazines via condensation-dehydrazinative ring transformation cascades

Abstract

The Cu(OTf)2-catalysed expeditious synthesis of 1,3-oxazin-2-ones(thiones) from unprotected D-glucose and D-xylose in excellent yields is reported. Cu(OTf)2 plays a dual role of a Lewis acid and an oxidant for dehydrazination, which is the cornerstone in the present investigation. The 1,3-oxazin-2-ones(thiones) serve as synthons for diversity oriented synthesis of structurally distinct bicyclic 1,3-oxazin-2-ones(thiones), when subjected to Malaprade reaction, followed by Cu(OTf)2-catalysed cyclisation with an appropriate traditional reagent such as phenylhydrazine, amidines, hydroxylamine, or semi(thiosemi)carbazide.