Electron‐Transfer and Hydride‐Transfer Pathways in the Stoltz–Grubbs Reducing System (KOtBu/Et₃SiH)

Abstract

Recent studies by Stoltz, Grubbs et al. have shown that triethylsilane and potassium tert‐butoxide react to form a highly attractive and versatile system that shows (reversible) silylation of arenes and heteroarenes as well as reductive cleavage of C−O bonds in aryl ethers and C−S bonds in aryl thioethers. Their extensive mechanistic studies indicate a complex network of reactions with a number of possible intermediates and mechanisms, but their reactions likely feature silyl radicals undergoing addition reactions and SH2 reactions. This paper focuses on the same system, but through computational and experimental studies, reports complementary facets of its chemistry based on a) single‐electron transfer (SET), and b) hydride delivery reactions to arenes.

N‐Silylation of Amines Mediated by Et3SiH/KOtBu

“…Although a broad network of reactions involving several intermediates and mechanisms has been proposed, the mechanistic diversity of this pair of reagents is still puzzling. We recently reported the Et 3 SiH/KO t Bu reagent in reductions of arenes and in cleavage of C−N bonds . In this article, we report our experimental and computational studies on the use of this reagent pair to silylate amines.…”

“…We recently reported the Et 3 SiH/KO t Bu reagent in reductions of arenes and in cleavage of CÀ N bonds. [31] In this article, we report our experimental and computational studies on the use of this reagent pair to silylate amines. Our publication at this stage is prompted by the appearance of a very recent patent in this area.…”

Benzylic C−H Functionalisation by [Et3SiH+KOtBu] leads to Radical Rearrangements in o‐tolyl Aryl Ethers, Amines and Sulfides

“…In 2013, Grubbs et al . reported that heating Et 3 SiH with KO t Bu afforded a novel reagent which has since been shown to carry out a wide range of chemical transformations . (Schemes and ).…”

“…at lower temperatures, cleavage of Ar−O bonds in aryl ethers 3 , and Ar−S bond cleavage in thioethers 5 at higher temperatures. In addition, the reagent debenzylates N‐benzylindoles, 7 , reduces fused aromatic hydrocarbons, ( e.g . 9 ) to their dihydro counterparts, and converts primary and secondary amines, e. g. 11 to their silylated derivatives, in this case, 12 .…”

“…In addition, the reagent debenzylates N‐benzylindoles, 7 , reduces fused aromatic hydrocarbons, ( e.g . 9 ) to their dihydro counterparts, and converts primary and secondary amines, e. g. 11 to their silylated derivatives, in this case, 12 . The analogous silane, Et 2 SiH 2 , (and less efficiently, Et 3 SiH) in combination with KO t Bu, converts styrenes, e. g. 13 to their hydrosilylated derivatives, in this case, 14 …”