Thiols as an Efficient Hydrogen Atom Donor in Free Radical Transformations in Aqueous Media

Abstract

This paper highlights several methods of C-C and C-H transfer reactions in aqueous media. In all cases, thiols play the role of the reducing agents. A variety of useful synthetic methodologies were also described, which occurred mainly via a free radical non-chain transfer processes. The potential usefulness of free radical reactions in water is demonstrated by ever-increasing studies over the last 5 years. In addition, a cis-trans lipid isomerization process under photoand gamma-irradiation conditions was reported. The complexity of the selective generation of thiyl radical in aqueous media and/or in biological milieus makes this topic highly important in chemistry, biology and medicine.

Reactivity of Biomass‐Derived Olefins with Elemental Sulfur: Mechanistic Insight

“…Heating an alkene in the presence of a radical‐producing species such as iodine at elevated temperatures is a common synthetic route for isomerizing alkenes [18] . Thiyl radicals are also reported to facilitate cis ‐/ trans ‐isomerism, [19] suggesting their similar participation in the reversible addition/elimination reactions necessary for olefin isomerism. In the current case, isomerization occurs by H‐atom abstraction from the allylic site by a sulfur‐centered radical then readdition of an H atom to the allyl radical to yield 1 g and 3 g (corresponding intermediates 2 g and 4 g were not observed).…”