121441-07-4Relevant articles and documents
Dynamics of the dimethyl sulfide exchange of (1,3-diphenylallyl)dimethylsulfonium ions
Jüstel, Patrick M.,Mayr, Herbert,Ofial, Armin R.,Rovó, Petra
, (2021/08/12)
The dynamics of the allylic rearrangement of the (1,3-diphenylallyl)dimethylsulfonium ion in CD2Cl2, which proceeds via intermediate 1,3-diphenylallyl cations, has been investigated by variable temperature 1H NMR spectroscopy. At low temperature, the three allylic protons give rise to an AMX system, and the two diastereotopic S-methyl groups resonate at different frequencies. At higher temperature, an AX2 system for the allylic protons and a single signal for the S-methyl groups are observed. The resulting exchange rate constant of (364 ± 2) s–1 at 25°C, which corresponds to the rate of the heterolytic cleavage of the C–S bond, was used to explore the range of validity of the linear free energy relationship log khet(25°C) = sf (Nf + Ef), which describes the rates of heterolytic cleavages by the electrofugality parameter Ef and the solvent-dependent nucleofuge-specific parameters Nf and sf. The observed rate constant corroborates a previous conclusion that two different sets of Nf and sf parameters may exist for the same nucleofuge. Knowledge of whether the reverse bond-forming reaction occurs under activation or under diffusion control is crucial for the choice of the appropriate set of nucleofugality parameters.
Asymmetric Synthesis Catalyzed by Chiral Ferrocenylphosphine-Transition-Metal Complexes. 8. Palladium-Catalyzed Asymmetric Allylic Amination
Hayashi, Tamio,Yamamoto, Akihiro,Ito, Yoshihiko,Nishioka, Eriko,Miura, Hitoshi,Yanagi, Kazunori
, p. 6301 - 6311 (2007/10/02)
Chiral ferrocenylphosphine ligands, represented by (R)-N-methyl-N--1-ethylamine ((R)-(S)-1a), which have a pendant side chain bearing a hydroxy group at the terminal position, were designed and used successfully for palladium-catalyzed asymmetric allylic amination of allylic substrates containing a 1,3-disubstituted propenyl structure (RCH=CHCH(X)R: R = Ph, Me, n-Pr, i-Pr; X = OCOOEt, OCOMe, OP(O)Ph2, etc.).Reaction of the allylic substrates with benzylamine in the presence of a palladium catalyst prepared in situ from Pd2(dba)3 and (R)-(S)-1a gave high yields of amination products (RCH=CHC*H(NHCH2Ph)R: >97percent ee (R) for R = Ph, 73percent ee (S) for R = Me, 82percent ee (S) for R = n-Pr, and 97percent ee (S) for R = i-Pr).The allylamines were converted into optically active amino acids and their derivatives.The high stereoselectivity of the ferrocenylphosphine ligand is expected to be caused by an attractive interaction between the terminal hydroxy group on the ligand and the incoming amine, which directs the nucleophilic attack on one of the ?-allyl carbons.The key role of the hydroxy group was supported by an X-ray structure analysis of a ?-allylpalladium complex and (31)P NMR studies.It was demonstrated that the pendant side chain on the ferrocenylphosphine ligand is directed toward the reaction site on palladium and the terminal hydroxy group is located at the position close to one of the ?-allyl carbon atoms and that ?-allyl group on the palladium coordinated with the ferrocenylphosphine 1a adopts one of the two possible conformational isomers with high selectivity (20/1) in an equilibrium state.
