- Ni- and pd-catalyzed synthesis of substituted and functionalized allylic boronates
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Two highly efficient and convenient methods for the synthesis of functionalized and substituted allylic boronates are described. In one procedure, readily available allylic acetates are converted to allylic boronates catalyzed by Ni/PCy3 or Ni/PPh3 complexes with high levels of stereoselectivity and in good yields. Alternatively, the borylation can be accomplished with commercially available Pd catalysts [e.g., Pd 2(dba)3, PdCl2, Pd/C], starting with easily accessed allylic halides.
- Zhang, Ping,Roundtree, Ian A.,Morken, James P.
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supporting information; scheme or table
p. 1416 - 1419
(2012/06/01)
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- Allylic C-H acetoxylation with a 4,5-diazafluorenone-ligated palladium catalyst: A ligand-based strategy to achieve aerobic catalytic turnover
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Pd-catalyzed C-H oxidation reactions often require the use of oxidants other than O2. Here we demonstrate a ligand-based strategy to replace benzoquinone with O2 as the stoichiometric oxidant in Pd-catalyzed allylic C-H acetoxylation. Use of 4,5-diazafluorenone (1) as an ancillary ligand for Pd(OAc)2 enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under 1 atm O 2. Mechanistic studies have revealed that 1 facilitates C-O reductive elimination from a π-allyl-PdII intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.
- Campbell, Alison N.,White, Paul B.,Guzei, Ilia A.,Stahl, Shannon S.
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supporting information; experimental part
p. 15116 - 15119
(2011/01/06)
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- Mechanistic investigations of bipyrimidine-promoted palladium-catalyzed allylic acetoxylation of olefins
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Several pyridine-like ligands were found to improve Pd(OAc) 2-catalyzed allylic oxidation of allylbenzene to cinnamyl acetate by p-benzoquinone in acetic acid. The best ligand examined, bipyrimidine, was used to identify the catalyst precursor for this system, (bipyrimidine)Pd(OAc) 2, which was fully characterized. Mechanistic studies suggest the reaction takes place through disproportionation of (bipyrimidine)Pd(OAc) 2 to form a bipyrimidine-bridged dimer, which reacts with olefin to form a PdII-olefin adduct, followed by allylic C-H activation to produce (η3-allyl)PdII species. The (η3-allyl)PdII intermediate undergoes a reversible acetate attack to generate a Pd0-(allyl acetate) adduct, which subsequently reacts with p-benzoquinone to release allyl acetate and regenerate (bipyrimidine)Pd(OAc)2. No KIE is observed for the competition experiment between allylbenzene-d0 and allylbenzene-d5 (CD2=CDCD2C6H5), suggesting that allylic C-H activation is not rate-determining. Catalytic allylic acetoxylations of other terminal olefins as well as cyclohexene were also effected by (bipyrimidine)Pd(OAc)2.
- Lin, Bo-Lin,Labinger, Jay A.,Bercaw, John E.
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experimental part
p. 264 - 271
(2009/10/23)
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- Regiospecific Preparation of Primary Allyl Acetates (2-Alkenyl Acetates)
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The reaction of primary, secondary and tertiary allyl alcohols 1 with anhydrous magnesium iodide in benzene gives regiospecifically the primary allyl iodides 2.The corresponding primary allyl acetates 3 are obtained regiospecifically by reaction of 2 with anhydrous sodium acetate in dimethylformamide.
- Martinez, Antonio Garcia,Villalobos, Angeles Cruces,Ruiz, Manuel Oliver
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- Herstellung und Isomerisierung von 1-Alken-3-yl-acetaten und 2-Alken-1-yl-acetaten
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The allylic rearrangement of 1-alken-3-yl acetates in acetic acid containing sodium acetate proceeds at a slower rate but in higher yield than the rearrangement in the presence of strong proton acids.The predominant products are 2-alken-1-yl acetates. (E)-2-Hexen-1-yl acetate can be isomerized to the (Z)-isomer or rearranged to 1-hexen-3-yl acetate via the epoxide, depending upon the conditions of reduction of the epoxide.
- Garcia Martinez, Antonio,Oliver Ruiz, Manuel,Contelles, Jose Luis Marco
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p. 125 - 128
(2007/10/02)
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