One-pot cyclizations of dilithiated oximes and hydrazones with epibromohydrin. Efficient synthesis of 6-hydroxymethyl-5,6-dihydro-4H-1,2-oxazines and oxazolo[3,4-b]pyridazin-7-ones

The one-pot cyclization of dilithiated oximes with epibromohydrin provided a convenient and regioselective approach to 6-hydroxymethyl-5,6-dihydro-4H-1,2-oxazines. The reaction of the latter with phosphorus tribromide resulted in a Beckmann rearrangement and formation of 5-bromomethyl-2-iminotetrahydrofurans. The reaction of dilithiated hydrazones with epibromohydrin afforded oxazolo3,4-b]pyridazin-7-ones, which were formed by a novel domino cyclization.