An Efficient Synthesis of 3-tert-Aminopropanol Derivatives by Regioselective Ring Opening of Tetrahydro-1,3-oxazines with Grignard Reagents

N-Benzyl tetrahydro-1,3-oxazines react with methylmagnesium iodide, benzylmagnesium bromide, allylmagnesium chloride and phenylmagnesium bromide affording 3-tert-aminopropanol derivatives with excellent yields. By contrast, the same substrates do no react with sodium phenylacetilide or butyllithium, and the corresponding tetrahydro-1,3-oxazinium methiodides are also inert toward Grignard reagents.