Nai-Wei Liu

Synthesis of Bromo-, Boryl-, and Stannyl-Functionalized 1,2-Bis(trimethylsilyl)benzenes via Diels–Alder or C–H Activation Reactions

1,2-Bis(trimethylsilyl)benzenes are key starting materials for the synthesis of benzyne precursors, Lewis acid catalysts, and certain luminophores. We have developed efficient, high-yield routes to functionalized 4-R-1,2-bis(trimethylsilyl)benzenes, starting from either 1,2-bis(trimethylsilyl)acetylene/5-bromopyran-2-one (2) or 1,2-bis(trimethylsilyl)benzene (1)/bis(pinacolato)diborane. In the first reaction, 5 (R = Br) is obtained through a cobalt-catalyzed Diels-Alder cycloaddition. The second reaction proceeds via iridium-mediated C-H activation and provides 8 (R = Bpin). Besides its use as a Suzuki reagent, compound 8 can be converted into 5 with CuBr(2) in i-PrOH/MeOH/H(2)O. Lithium-bromine exchange on 5, followed by the addition of Me(3)SnCl, gives 10 (R = SnMe(3)), which we have applied for Stille coupling reactions. A Pd-catalyzed C-C coupling reaction between 5 and 8 leads to the corresponding tetrasilylbiphenyl derivative. The bromo derivative 5 cleanly undergoes Suzuki reactions with electron-rich as well as electron-poor phenylboronic acids.

Radicals and Sulfur Dioxide: A Versatile Combination for the Construction of Sulfonyl-Containing Molecules

Molecules containing a sulfonyl functionality, such as sulfones, sulfonyl chlorides or sulfonamides play an important role in organic chemistry and have found widespread application, especially in the construction of biologically active compounds. Recently, methods for the synthesis of the sulfonyl moiety utilizing sulfur dioxide as a key building block have received considerable attention. In this context, radical-based transformations with sulfur dioxide have emerged as a new and attractive approach for the construction of the sulfonyl functional group. This short review highlights recent advances in the use of sulfur dioxide in radical reactions and covers the historical background, which forms the basis for these current progresses. Limitations of the existing methods and potential further developments will be discussed.

Visible-light mediated 3-component synthesis of sulfonylated coumarins from sulfur dioxide

A novel 3-component synthesis of sulfonylated coumarins from diaryliodonium salts, arylpropynoates and sulfur dioxide is reported. The reaction proceeds under mild conditions at room temperature in the absence of any catalysts. This transformation is solely driven by visible light and opens a new opportunity for the sustainable synthesis of sulfones via the direct incorporation of sulfur dioxide.

Visible-Light Photoredox/Nickel Dual Catalysis for the Cross-Coupling of Sulfinic Acid Salts with Aryl Iodides

An efficient cross-coupling of sodium or lithium sulfinates with aryl iodides, using a combination of nickel and photoredox catalysis, is described. The dual catalyst system enables a versatile synthesis of aryl sulfones at room temperature in good yields and displays a broad functional group compatibility. The potential utility of this method in the late-stage diversification of complex molecules and in the conversion of organolithium reagents and sulfur dioxide into sulfones is demonstrated.