Pd-Catalyzed Multicomponent Cross-Coupling of Allyl Esters with Alkyl Bromides and Potassium Metabisulfite: Access to Allylic Sulfones.

A Pd-catalyzed multicomponent cross-coupling of allyl esters with alkyl bromides to synthesize allylic sulfones by using K2S2O5 as a connector is first reported. The reaction displays a broad range of substrate generality along with excellent functional group compatibility and produces the products with high regioselectivity (only E). Furthermore, the biologically active molecules with a late-stage modification, including aspirin, menthol, borneol, and estrone, are also highly compatible with the multicomponent cross-coupling reaction. Mechanistic studies indicate that the process of SO2 insertion into the C-Pd bond was involved in this transformation.

Multicomponent Sulfonylation of Alkenes to Access ß-Substituted Arylsulfones.

A novel multicomponent sulfonylation of alkenes is described for the assembly of various ß-substituted arylsulfones using cheap and easily available K2S2O5 as a sulfur dioxide source. Of note, the procedure does not need any extra oxidants and metal catalysts and exhibits a relatively wide substrate scope and good functional group compatibility. Mechanistically, an initial arylsulfonyl radical is formed involving the insertion of sulfur dioxide with aryl diazonium salt, followed by alkoxyarylsulfonylation or hydroxysulfonylation of alkenes.

Copper(I)-Catalyzed Cross-Coupling of Arylsulfonyl Radicals with Diazo Compounds: Assembly of Arylsulfones.

A novel copper-catalyzed cross-coupling of arylsulfonyl radicals with diazo compounds is described for the synthesis of various arylsulfones under mild conditions. In this reaction, the cheap, environmentally friendly, and readily available inorganic K2S2O5 is employed as the sulfur dioxide source for providing arylsulfonyl radicals. In addition, a radical mechanism involving the insertion of sulfur dioxide with aryl radicals followed by the coupling of arylsulfonyl radicals with copper carbenes is proposed.

Radical-Mediated Cascade Spirocyclization of N-Benzylacrylamides with Polyhaloalkanes: Access to Polyhalo-Substituted Azaspirocyclohexadienones.

A novel and mild metal-free catalyzed radical-mediated cascade spirocyclization of N-benzylacrylamides with polyhaloalkanes is proposed for the preparation of polyhalo-substituted azaspirocyclohexadienones. Notably, polyhaloalkanes are employed as efficient alkyl radical sources via the cleavage of C(sp3)-H bonds. This protocol undergoes a cascade radical addition and intramolecular cyclization/dearomatization process, and enables the easy construction of multiple chemical bonds and a spiro ring in a single reaction.

Palladium-catalyzed difunctionalization/dearomatization of N-benzylacrylamides with α-carbonyl alkyl bromides: facile access to azaspirocyclohexadienones.

An efficient palladium-catalyzed difunctionalization/dearomatization of N-benzylacrylamides with α-carbonyl alkyl bromides as alkyl radical precursors has been described. Various α-carbonyl alkyl bromides, including α-bromoalkyl esters and ketones, reacted smoothly to provide important azaspirocyclohexadienones in moderate to excellent yields. In addition, mechanistic studies suggested that the reaction proceeded via a radical pathway.