Silylation of Allylic Trifluoroacetates and Acetates Using Organodisilanes Catalyzed by Palladium Complex

Abstract

Silylation of allylic acetates (1) using organodisilanes (2) was carried out in the presence of a catalytic amount of Pd(DBA)2−LiCl at 100 °C. The silylation proceeded smoothly without β-hydrogen elimination of a resulting (π-allyl)palladium intermediate. The added chloride salt such as LiCl or NaCl was indispensable for the catalytic activity. On the other hand, remarkable improvement of the silylation was realized by employing allylic trifluoroacetates (4) in place of the acetates (1) as the substrates. The silylation proceeded even at room temperature, and the added chloride salts was not necessary as the catalyst component. In the silylation, transmetalation of the disilanes (2) with (η3-allyl)palladium intermediate (7) might be a critical step in the catalytic cycle. Model reactions for the transmetalation were carried out.

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

“…The reactivity profile of allylic carbonates differ from other allylic substrates in coupling reactions [11][12][13][14][15][16][17][18][19][20][21][22]. The coupling reaction of allylic carbonate in the presence of palladium catalyst usually involves p-allylpalladium(II) intermediate species [17] through the initial oxidative addition of allylic carbonate to Pd(0) with subsequent loss of carbon dioxide.…”

“…The cross-coupling reactions of various allylic substrates with organo-boron, -tin, -silicon, -indium, etc. reagents were reported under palladium-catalyzed conditions [11][12][13][14][15][16][17][18][19][20][21][22]. However, recently triarylbismuths have been demonstrated to be useful as multi-coupling organometallic nucleophiles for atom-efficient couplings with organic electrophiles [23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Desilylation and conversion of trimethylsilylmethyl epoxides into ketones under the influence of a bulky base

“…Trimethylsilyl olefin 3a was prepared from cinnamyl alcohol 1a through esterification with trifluoroacetic anhydride and coupling with hexamethyldisilane (TMS) 2 under palladium(0)-catalysis by a procedure described in the literature [10]. Allylic alcohols 1b,c were prepared from reactions of vinylmagnesium bromide and cyclohexanecarboxaldehyde and heptanal, respectively.…”

“…Allylic alcohols 1b,c were prepared from reactions of vinylmagnesium bromide and cyclohexanecarboxaldehyde and heptanal, respectively. After esterification with trifluoroacetic anhydride, their esters underwent a rearrangement and coupling with hexamethyldisilane (TMS) 2 under palladium(0)-catalysis to produce trimethylsilyl olefins 3b,c [10]. The trimethylsilyl olefins 3 were converted into trimethylsilylmethyl epoxides 4 in high yields by oxidation with di(chloromethyl)dioxirane, generated in situ from 1,3-dichloroacetone and Oxone (potassium peroxomonosulfate) [11].…”

Allylation of Aldehyde and Imine Substrates with in situ Generated Allylboronates — A Simple Route to Enantioenriched Homoallyl Alcohols.

“…[26,27] The next step is addition of the diboron reagent to the allyl moiety of 9b to form the transient allylboronate 11. Considering these type of reactions with analog dimetal reagents, [10,[17][18][19][28][29][30] such as hexaalkyl/aryldisilanes (R 3 Si-SiR 3 ) and distannanes (R 3 Sn-SnR 3 ) the boron-carbon bond formation probably takes place by a inner-sphere nucleophilic attack. Thus the nucleophilic attack is preceded by formation of complex 13, in which the boronate group is coordinated to palladium.…”