Radical Hydrometalation of Functional Ethylenic Compounds:  Radical Autoinhibition Changes the Regioselectivity

Abstract

Hydrometalation of carbon−carbon double bonds by group 14 hydrides is inhibited by carbonyl compoundsmainly by α,β-unsaturated carbonyl groupsas efficiently as by classical radical trapping compounds, such as galvinoxyl and hydroquinone. This phenomenon, in the case of polyfunctional CC- and CO-containing compounds, such as carvone, leads to an autoinhibition of the exocyclic alkenylic hydrometalation under normal reaction conditions, while under drastic conditions, the O-metalation of the α,β-unsaturated carbonyl group occurs.

Hydrosilylation of unsaturated fatty acid N‐phenyl amides

“…A comparable effect has indeed been shown recently in functional ethylenic compounds (limonene, carveol, carvone) 21 and has been studied in detail.…”

“…However, no reaction occurred between triethoxysilane and oleic acid anilide 2 using either Karstedt's catalyst or radical initiation (AIBN or radical initiation sequence, RIS). 21 Such a low reactivity of the internal double bond of fatty acid esters was previously reported in the case of hydrosilylation of ethyloleate:…”

“…Additionally, using Ph 3 GeH, which is more reactive than Cl 3 SiH in radical processes, 21,23 no reaction occurred in the same experimental conditions. This totally unanticipated result encouraged us to analyze this reaction in detail.…”

“…Unexpectedly, the use of the more reactive trichlorosilane, 7 and of drastic procedures (RIS) 21 followed by treatment by ethanol in the presence of triethylamine yielded cleanly, after elimination of Et 3 N.HCl, the desired triethoxysilylated compound 7 [equation (5)]. …”

Silylation of triacylglycerol: an easy route to new biosiloxanes

“…Initiators were used in a 5% concentration relative to organic reagents. Radical initiation sequence (RIS) was done with a 1/1/1 mixture of radical initiators: azo-bis isobutyronitrile (AIBN, (Me 2 C(CN)-N ) 2 ), t-butyl perbenzoate (Ph-C(O)O-Ot-Bu) and di-t-butyl peroxide (t-BuO-OtBu) in a programmed range of temperature from 20 to 150 • C (El Kadib et al, 2005b). Karstedt's catalyst [Pt 0 ] [platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, 0.100 M in poly(dimethylsiloxane)] was used in a 1% concentration relative to organic reagents.…”