Reactions of vinyl silanes with palladium salts - vinyl heck reactions

<b>Thermal decomposition of vinyl- and allylsilane platinum(II) complexes and platinum(II)catalysed synthesis of (<i>E</i>),(<i>E</i>)-1,4-diphenyl-1,3-butadiene</b>

“…Solvent was removed from the filtrate (GC analysis indicated the presence of chlorotrimethylsilane) and the residue was crystallised from pentane to give tan crystals of (E),(E)-1,4-diphenyl-1,3-butadiene 4 in 65 % yield and m.p. 150-151 o C. The IR and 1 H NMR spectra of the product were in agreement with those in the literature [6].…”

“…(150-152 o C), 1 H NMR and IR spectra, which were identical to those of a sample prepared by use of a Pd based catalyst [6]. The reaction is stereoselective and gave a good yield of 4.…”

Pd‐Promoted Homocoupling Reactions of Unsaturated Silanes in Aqueous Micelles

“…As previously reported, [9,16] silanes 1 afford dimerization products 2 (Scheme 1) with yields ranging from 30 to 61 % by treatment with catalytic [16] to substoichiometric [9] amounts of PdCl 2 in methanol or HMPA, in the presence of a large excess of CuCl 2 and LiCl, which are necessary to reoxidize the Pd 0 generated in the reductive elimination step leading to the new carbon-carbon bond formation. The reaction is highly stereoselective, affording only the all-E stereoisomer of the product polyenes.…”

“…In these conditions, the reaction produces stereoselectively the dimerization product (1E,3E)-1,4-bis(p-tolyl)butadiene 4 with unexpectedly high yield (87 %) compared with the yields obtained when the reactions were carried out in MeOH or HMPA. [9,16] The increased yield is due to the suppression of proto-and chlorodesilylation side reactions which negatively affect the process in non-micellar conditions. [9,16] Inhibition of protodesilylation can be attributed to the lipophilic nano-environment of the micellar core which protects the organic substrate from the reaction with HCl and likely reduces or eliminates its formation.…”

“…[9,16] The increased yield is due to the suppression of proto-and chlorodesilylation side reactions which negatively affect the process in non-micellar conditions. [9,16] Inhibition of protodesilylation can be attributed to the lipophilic nano-environment of the micellar core which protects the organic substrate from the reaction with HCl and likely reduces or eliminates its formation. Similarly, the CuCl 2 salt responsible for the chlorodesilylation reaction would not enter the lipophilic core of the micelles.…”