850-61-3Relevant academic research and scientific papers
Linear free-energy relationship and rate study on a silylation-based kinetic resolution: Mechanistic insights
Akhani, Ravish K.,Moore, Maggie I.,Pribyl, Julia G.,Wiskur, Sheryl L.
, p. 2384 - 2396 (2014/04/17)
The substituent effect of different p-substituted triphenylsilyl chlorides on silylation-based kinetic resolutions was explored. Electron-donating groups slow down the reaction rate and improve the selectivity, while electron-withdrawing groups increase the reaction rate and decrease the selectivity. Linear free-energy relationships were found correlating both selectivity factors and initial rates to the σpara Hammett parameters. A weak correlation of selectivity factors to Charton values was also observed when just alkyl substituents were employed but was nonexistent when substituents with more electronic effects were incorporated. The rate data suggest that a significant redistribution of charge occurs in the transition state, with an overall decrease in positive charge. The linear free-energy relationship derived from selectivity factors is best understood by the Hammond postulate. Early and late transition states describe the amount of substrate participation in the transition state and therefore the difference in energy between the diastereomeric transition states of the two enantiomers. This work highlights our efforts toward understanding the mechanism and origin of selectivity in our silylation-based kinetic resolution.
Preparation, characterization and properties of dipolar 1,2-N,N-dimethylaminomethylferrocenylsilanes
Beyer, Christian,B?hme, Uwe,Pietzsch, Claus,Roewer, Gerhard
, p. 187 - 201 (2007/10/03)
A series of substituted 1,2-N,N-dimethylaminomethlyferrocenyl compounds were synthesized and characterized by 1H-NMR, 13C-NMR, 29Si-NMR, ES-MS, IR, UV - vis and 57Fe-M?ssbauer spectroscopy. The new (R,S)-2-(N,N-dimethylaminomethyl)ferrocenyl-(arly)silanes (R,S)-FcNSiMen(C6H4X)m (n = 2-0, m = 1, X = p-F (5); m = 2, X = p-F (6); m = 3, X = p-F (7) and m = 1, X = p-Br (14) were formed by the reaction of 2-dimethylaminomethylferrocenyllithium FcNLi (1) with chloroarylsilanes ClSi(Me)n (C6H4X)m (n = 2-0, m = 1, X = p-F (2); m = 2, X = p-F (3); m = 3, X = p-F (4) and m = 1, X = p-Br (13)). The treatment of 5, 6 and 14 with gaseous hydrogen chloride or picric acid resulted in the formation of the hydrochloride complexes 9, 10, 15 and the picrates 11, 12 and 16. The treatment of 14 with LiR or Mg and DMF resulted in the formation of (R,S)-2-(N,N-dimethylaminomethyl)ferrocenyl(4-formylphenyl)dimethylsilane (18). The crystal structures of 7, 12 and 15 were determined by single crystal X-ray analyses. 57Fe-M?ssbauer spectroscopy gives evidence of a significant electronic coupling between the ferrocenyl unit and the organic acceptor moiety of the molecules in the ground state.
