Regioselectivity of Radical Addition of Thiols to 1‐Alkenes

Abstract

The addition of dodecanethiol (1) to 1‐alkenes H2C=CHR that have substituents R = Hex, (CH2)8COOMe, Ph, Bn, cHex, CH2cHex, tBu (2a–2g) with different steric effects was studied. Some few percent of branched Markovnikov addition product 4 was formed in all cases with the exemption of styrene (2c) in addition to linear anti‐Markovnikov product 3 as the main product. The regioselectivities correlate well with the Taft steric parameter ES of the R‐substituent at the alkene. This gives evidence that the regioselective outcome of the radical addition of thiols to 1‐alkenes is mainly steered by the steric effect of the R‐substituent as it is well known for the addition of alkyl radicals to alkenes. In the case of thiol addition, however, the regioselectivity is strongly enhanced by the much faster fragmentation of the intermediate Markovnikov than of the anti‐Markovnikov adduct radical.

Fatty Acid–Derived Aliphatic Long Chain Polyethers by a Combination of Catalytic Ester Reduction and ADMET or Thiol‐Ene Polymerization

“…After zooming into the spectra, a multiplet can be discerned at ≈2.75-2.61 ppm and might be assigned to the methine proton formed by the unflavored Markovnikov addition of thioacetic acid as minor side product formed in amounts between 1.4 and 5.6%, depending on the monomer. These findings are in agreement to previous results regarding the regioselectivity of radical addition of thiols to 1-alkenes [22] ; however, exact quantification by 1 H-NMR spectroscopy is difficult because trace amounts of residual disulphide also might give a signal at 2.71-2.64 ppm as well as small satellite peaks of the thiol signal at 2.50 ppm.…”

Radical‐Mediated Approaches for the Synthesis of Thiolactones

“…This radical reaction is believed to proceed via a Molecule Induced‐Homolysis (MIH) pathway (Scheme 5). [28] Coordination of the thiol to the alkene via H‐bonding forms an Electron Donor‐Acceptor complex (EDA complex) which facilitates the HAT from the thiol to the alkene generating a thiyl radical, and an unproductive C‐centered radical. This C‐centered radical can abstract a hydrogen from a thiol generating another thiyl radical while giving a reduced side‐product.…”

Research Progress in C—S Bond Formation Reaction of Olefins with Organic Sulfur Reagents under Photocatalyst-Free and Non-Electrochemical Conditions

“…最后, 该碳自由基从反应体系中捕获氢原子成为饱 和烃. 不仅如此, Metzger 课题组 [16] 还发现硫醇与烯烃的 硫醚化反应还可以在无添加剂、无溶剂的条件下进行, 并且产率较高(Eq. 2).…”