344336-46-5Relevant academic research and scientific papers
N-Heterocyclic carbenes as ligands in palladium-catalyzed Tsuji-Trost allylic substitution
Sato, Yoshihiro,Yoshino, Taro,Mori, Miwako
, p. 5753 - 5758 (2007/10/03)
A Pd(0)-catalyzed allylic substitution (i.e., Tsuji-Trost reaction) using N-heterocyclic carbene as a ligand was investigated. It has been proven that an imidazolium salt 2d having bulky aromatic rings attached to the nitrogens in its imidazol-2-ylidene skeleton is suitable as a ligand precursor and that a Pd2dba3-imidazolium salt 2d-Cs2CO3 system is highly efficient for producing a Pd-NHC catalyst in this reaction. Allylic substitution using a Pd-NHC complex differed from that using a Pd-phosphine complex as follows: (1) the reaction using a Pd-NHC complex required elevated temperature (50 °C or reflux in THF), (2) allylic carbonates were inert to a Pd-NHC complex, and (3) nitrogen nucleophiles such as sulfonamide and amine did not react with allylic acetate. It was also found that allylic substitution with a soft nucleophile using a Pd-NHC catalyst proceeds via overall retention of configuration to give the product in a stereospecific manner, the stereochemical reaction course obviously being the same as that of the reaction using a Pd-phosphine complex.
Pd-catalyzed allylic substitution using nucleophilic N-heterocyclic carbene as a ligand
Sato, Yoshihiro,Yoshino, Taro,Mori, Miwako
, p. 31 - 33 (2007/10/03)
(Matrix presented) A nucleophilic N-heterocyclic carbene has been successfully used in a Pd(0)-catalyzed allylic substitution for the first time. It was found that allylic substitution with a soft nucleophile using a Pd-carbene catalyst proceeds via retention of configuration, the stereochemical reaction pathway being the same as that of the reaction using a Pd-phosphine complex.
Allylic alcohols as substrates for the palladium(0)-catalyzed allylic substitution
Stary,Stara,Kocovsky
, p. 179 - 182 (2007/10/02)
A new method has been developed which allows palladium(0)-catalyzed allylic substitution to occur between allylic alcohols and anionic C-nucleophiles: on reaction with Ph3B, the allylic alkoxide 7 is first converted in situ into the more reactive species 8 which then undergoes a Pd(0)-catalyzed reaction with lithiodiethyl malonate via the η3-complex 9.
Isomerization of (πr-allyl)palladium complexes via nucleophilic displacement by palladium(0). A common mechanism in palladium(0)-catalyzed allylic substitution
Granberg, Kenneth L.,B?ckvall, Jan-E.
, p. 6858 - 6863 (2007/10/02)
Treatment of (π-allyl)palladium complexes such as 6 and 9 with Pd(PPh3)4 leads to rapid isomerization at -15 °C in tetrahydrofuran and other solvents. At 0°C and in the presence of more than 2 equiv of triphenylphosphine per palladium, the phosphine attacks the T-allyl group to give allylic phosphonium salts 7 with concomitant formation of a palladium(0)-phosphine complex, and isomerization of 6 is observed. Attack by PPh3 on 6 was shown to be stereospecific and to proceed with inversion. Studies of the Pd(0)-catalyzed substitution of le (X = OAc) with several different nucleophiles support the hypothesis that Pd(0) acts as a nucleophile on (π-allyl)palladium complexes, in a reaction that leads to loss of stereospecificity in these systems.
