Regio‐ and Stereoselective Approach to 1,2‐Di‐ and 1,1,2‐Trisilylethenes by Cobalt‐Mediated Reaction of Silyl‐Substituted Dibromomethanes with Silylmethylmagnesium Reagents

Abstract

Functional ethenes: Treatment of dibromo(silyl)methanes 2 a with silylmethyl Grignard reagents 1 and catalytic CoCl2 affords (E)‐1,2‐disilylethenes 3 a in excellent yields. Dibromodisilylmethanes 2 b undergo a similar transformation to furnish trisilylethenes 3 b with excellent stereo‐ and regioselectivity in the presence of a stoichiometric amount of a cobaltate reagent.

Advances in disilylation reactions to access cis/trans-1,2-disilylated and gem-disilylated alkenes

“…In 2005, the Oshima group introduced a novel method for the synthesis of 1,1,2-trisilylethenes through cobalt-catalyzed disilylation of silyl-containing Grignard reagent using dibromodimethylsilane 41 as the gem -disilyl group precursor (Scheme 27). 172 1,1,2-Trisilylethenes could be efficiently obtained by using the stoichiometric silylcobalt reagent [(R 3 SiCH 2 ) 4 Co(MgCl) 2 ], which was derived from Co( ii ) chloride and a silyl-containing Grignard reagent. This reaction proceeded smoothly with (Me 3 Si) 2 CBr 2 as the disilicon source, yielding the desired gem -disilylated products in good yields.…”

(Z)‐1,2‐bis(ethoxydimethylsilyl)arylethenes as new building blocks for organic synthesis

“…Several independent methods, e.g. cobalt‐mediated reaction of silyl‐substituted dibromomethanes with silylmethylmagnesium reagents9 or copper‐catalyzed silylzincation of silylacetylenes10 and silylcupration of acetylenes11 have also been investigated. However, in many cases, application of these methods has been limited because of difficulties in accessing stereo‐ and regiodefined isomers, owing to the possibility of formation of a mixture of two [1,2‐( Z ) and 1,2‐( E ) in bissilylation] or three [1,2‐( Z ), 1,2‐( E ) and 1,1‐ in hydrosilylation] isomeric bis(silyl)ethenes.…”

Experimental and Computational Studies of the Iron‐Catalyzed Selective and Controllable Defluorosilylation of Unactivated Aliphatic gem‐Difluoroalkenes

“…Them echanism of the disilylation of the second C À Fb ond was completely different from the previous reports, [15e,20] in which the nucleophilic substitution by NaSiEt 3 was proposed. Thedisilylation proceeded through the nucleophilic addition of NaSiEt 3 to 5 III-a (17.0 kcal mol À1 ) promoted by the in situ L 5 FeÀFs pecies,f ollowed by elimination of NaF. [21] In contrast, the activation energy would increase to 29 kcal mol À1 under a s-bond metathesis mechanism without Fe À Fs pecies assistance (see Supporting Information Figure S4).…”