Reactions of Ruthenium−Benzylidene Complexes with Bis(trimethylsilyl)ethene and Trimethylsilylstyrenes:  Olefin Metathesis versus β-SiMe₃ Elimination/Reductive Elimination

Abstract

The benzylidene complexes [Cl 2 (PCy 3 ) 2 RudC(C 6 H 4 R-p)H] [R ) H (1a), Cl (1b), OMe (1c)] react with (E)-bis(trimethylsilyl)ethene (2) to give 3,3-bis(trimethylsilylAnalogously, reaction of 1a with trimethylsilylstilbene gives H(Ph)CdC(SiMe 3 )H (4a). In contrast, reaction of 1a with para-methoxysubstituted trimethylsilylstilbene, H(Me 3 Si)CdC(C 6 H 4 OMe-p)H (4b), affords mixtures of the crossmetathesis product, H(Me 3 Si)CdC(Ph)H, and various propene derivatives. Labeling experiments have been carried out. The mechanism of these reactions is discussed.

Regioselectivity of Stoichiometric Metathesis of Vinylsilanes with Second-Generation Grubbs Catalyst: A Combined DFT and Experimental Study

“…In general, the postreaction mixture contains a variety of components that are products of pathways a and b, products of vinylsilane homometathesis (when applied) as well as products of potential β-silylsubstituted ruthenacyclobutane decomposition via β-SiR 3 elimination (Scheme ). ,, …”

“…For SiR 3 = SiMe 3 , β-silyl-substituted ruthenacyclobutane formed in pathway a (Scheme ) undergoes cycloreversion, leading to silylstyrene, but there is also a tendency for decomposition via β-SiR 3 elimination (Scheme ). ,, Being competitive to cycloreversion, β-elimination affects the silylstyrene to styrene ratio. Thisis why for SiR 3 = SiMe 3 it was assumed that a measure of the kinetic preference for pathway a or b is the ratio of the sum of concentrations of silylstyrene and (phenyl,silyl)-substituted propenes, formed via β-elimination (Scheme ), to the concentration of styrene, monitored in the first stage of the reactions.…”

Isotopic probes for ruthenium-catalyzed olefin metathesis

“…23 To date, however, Grubbs catalysts bearing an isotopic label at the alkylidene site are limited to deuterated derivatives. [24][25][26][27] Here we report routes to the 13 C-labelled analogues, for both first-and secondgeneration Grubbs catalysts (Fig. 1a).…”

Jüngste Entwicklungen bei der gekreuzten Olefinmetathese

“…Fischer et al [56] stellten bei Reaktionen von Vinyltrialkoxysilanen mit 6 in stöchiometrischen Mengen die hochselektive Bildung von PhCH¼CHSi(OR) 3 Roy et al beschrieben die Anwendung einer selektiven CM als C-C-verknüpfender Schlüssel-schritt bei der Synthese "molekularer Sternchen" ("molecular asterisks"). [62] Zunächst wurde in einer CM peracetyliertes Allyl-a-d-galactopyranosid (70) …”