Visible light photooxidative cyclization of amino alcohols to 1,3-oxazines

1,3-Amino alcohols were prepared to examine how structure affects the oxidation of tertiary amines in visible light photocatalysis. These substrates were cyclized to produce oxazines following the photooxidative formation of iminium ions using catalytic Ru(bpy)3Cl2. Amino alcohol derivatives of tetrahydroisoquinoline, tetrahydroquinoline, pyrrolidine, and Δ3-piperidine all were found to be viable substrates. In the case of the unsaturated piperidines, cyclization is accompanied by addition of methanol across the alkene; most likely occurring via a conjugate addition to an intermediate α,β-unsaturated iminium ion prior to oxazine formation.