Copper-Catalyzed Synthesis of Thiadiazine-1-oxides in Reusable Aqueous Medium under External [Ag]/Ligand/Base-Free Conditions.

We report herein a copper-catalyzed multicomponent reaction of simple NH-sulfoximine with readily available aldehyde and TMSN3 in hot water and aerobic conditions. The reaction tolerated a broad range of functional groups under external [Ag]/ligand/base-free conditions and can form three C-N bonds in a one-pot transformation, thus representing an extremely cost-effective protocol to biologically active sulfoximine derivatives. This aqueous catalytic system could be circularly utilized in consecutive runs of gram-scale preparations of thiadiazine-1-oxides without extra addition of the copper catalyst and PTA. Mechanistically, an ″ortho-binding″ effect in ortho-bromo NH-sulfoximine was proposed to control the chemoselectivity; thus, the other free halides such as bromo- or iodo-atoms in aldehydes 2 were compatible in the reaction.