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A rapid and convenient palladium catalysed method for the regioselective synthesis of a range of usefully functionalised, homochiral 4-substituted 1,2-isothiazoline-3-ones is reported. The totally diastereoselective Diels-Alder reactivity of semi-cyclic sulfoxide containing dienes, 4-vinyl-1,2-isothiazoline-3-one-1-oxides is discussed.

Activated 2-(N-acylamino)-1-thia-1,3-dienes undergo efficient diastereoselective Diels-Alder cycloadditions giving access to thiopyrans of high optical purity. By variation of the position and nature of the chiral auxiliaries we have been able to induce a high degree of facial selectivity in endo selective cycloadditions and induce total facial control in exo selective cycloadditions.

4-Phenyl-2-N-(R-(−)-α-(2-naphthyl)ethylamino)-1-thia-1,3-dienes when activated by acetyl chloride, undergo extremely efficient diastereoselective exo Diels-Alder cycloadditions giving access to thiopyrans of high optical purity.

Semi cyclic sulphoxide containing dienes, 4-vinyl- 1,2-isothiazoline-3-one-1-oxides, generated in situ via Stille coupling methodology dimerise with remarkably high diastereoselectivity via an unusual exo syn transition state. X-ray analysis confirms the diastereoselectivity which was predicted by semi-empirical transition state calculations.

A rapid and convenient palladium catalysed method for the regioselective synthesis of a range of usefully functionalised, homochiral 4-substituted 1,2-isothiazoline-3-ones is reported.

[reaction--see text] [corrected] The preparation and thermolysis of new stable heterocyclic precursors of 1,2-diaza-1,3-butadienes is described. The resulting reactive diazadienes are trapped in situ with N-phenylmaleimide [corrected]. The effect of precursor structure on the temperature at which the diazadienes are generated is discussed.

[reaction--see text] A novel Pd(0)-catalyzed carbonylation of both isolable 1,2-diaza-1,3-butadienes and those generated in situ by extrusion of SO(2) and CO(2) from heterocyclic precursors is described. The reaction proceeds at room temperature to 110 degrees C under 1-2 atm of CO to afford 2,3-pyrazol-1(5H)-ones in good to excellent yields. The effect of catalyst structure and stability on the carbonylation reaction is evaluated.