Cyclic and acyclic sulfonimides in reactions with Rh(II)-ketocarbenoids: a new access to chemoselective O-functionalization of the imidic carbonyl groups.

Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and 1H- and 13C-NMR studies it was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution. Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process.