Progress on Biological Activity Study and Enantioselective Synthesis of Sulfoxides

Synthesis of Sulfoxides by Palladium-Catalyzed Arylation of Sulfenate Anions with Aryl Thianthrenium Salts

A novel and highly efficient Pd-catalyzed arylation of sulfenate anions with aryl thianthrenium salts is demonstrated. This procedure provides a practical protocol to synthesize various diaryl and alkyl aryl sulfoxides in moderate-to-good yields. The new approach shows mild reaction conditions, broad substrate scope, and good functional group tolerance.

Enzymatic Resolution and Decarboxylative Functionalization of α-Sulfinyl Esters

α-Sulfinyl esters can be readily prepared through thiol substitution of α-bromo esters followed by oxidation to the sulfoxide. Enzymatic resolution with lipoprotein lipase provides both the unreacted esters and corresponding α-sulfinyl carboxylic acids in high yields and enantiomeric ratios. Subsequent decarboxylative halogenation, dihalogenation, trihalogenation and cross-coupling gives rise to functionalized sulfoxides. The method has been applied to the asymmetric synthesis of a potent inhibitor of 15-prostaglandin dehydrogenase.

Asymmetric Synthesis of S(IV) and S(VI) Stereogenic Centers

Sulfur can form diverse S(IV) and S(VI) stereogenic centers, of which some have gained significant attention recently due to their increasing use as pharmacophores in drug discovery programs. The preparation of these sulfur stereogenic centers in their enantiopure form has been challenging, and progress made will be discussed in this Perspective. This Perspective summarizes different strategies, with selected works, for asymmetric synthesis of these moieties, including diastereoselective transformations using chiral auxiliaries, enantiospecific transformations of enantiopure sulfur compounds, and catalytic enantioselective synthesis. We will discuss the advantages and limitations of these strategies and will provide our views on how this field will develop.

Access to Sulfoxides under NHC/Photocatalysis via a Radical Pathway

A photocatalyzed transformation from sulfinic acids to sulfoxides under visible-light irradiation in the presence of N-heterocyclic carbene is established. Various alkyl groups from four-substituted Hantzsch esters or Meyer nitriles are smoothly converted to the corresponding sulfoxides through a radical coupling pathway in the presence of 1,1-carbonyldiimidazole. This method allows sulfoxide synthesis to refrain from relying on the oxidation of sulfides and provides an alternative route for the preparation of sulfoxides.