Sulfur dioxide mediated one-pot, four-component synthesis of polyfunctional sulfones and sulfonamides, including medium-ring cyclic derivatives

In previous papers (Synthesis 2002, 232 and J. Org. Chem. 2004, 69, 6413), we have shown that the hetero-Diels–Alder addition of sulfur dioxide to 1-oxy or 1,3-dioxy-1,3-dienes generates zwitterions that add to enoxysilanes or allylsilanes giving silyl sulfinates that can be converted in the same pot into polyfunctional sulfones, sulfonamides or sulfonic esters. We are presenting further applications of this method, including the synthesis of new medium-size heterocyclic systems of the type tetrahydro-2H-thiocines and hexahydro-1,2-thiazonine.