1,2-Thiazines and related heterocycles. Part 5. Characterisation of some (N-sulphinylamino)azines and their cycloadducts with 1,4-epoxy-1,4-dihydronaphthalenes and other dienophiles

Abstract

A range of (N-sulphinylamino)azines has been synthesized and characterised, most for the first time. These heterocycles cycloadd as heterodienes to 1,4-epoxy-1,4-dihydronaphthalenes and similar electron-rich dienophiles through the sulphur atom of the sidechain and an ortho position of the azine ring. When the azine is unsymmetrically functionalised the cycloadditions are strongly periselective: 2-(N-sulphinylamino)pyridine reacts at the ring nitrogen, a preference that is not overturned by the introduction of steric hindrance; 3-(N-sulphinylamino)pyridine reacts at C-2 of the azine but addition may be diverted to C-4 by methylation at C-2. Regioselective additions to unsymmetrical dienophiles are also observed.