- Deprotonative Silylation of Aromatic C-H Bonds Mediated by a Combination of Trifluoromethyltrialkylsilane and Fluoride
-
A method for the deprotonative silylation of aromatic C-H bonds has been developed using trifluoromethyltrimethylsilane (CF3SiMe3, Ruppert-Prakash reagent) and a catalytic amount of fluoride. In this reaction, CF3SiMe3 is considered to act as a base and a silicon electrophile. This process is highly tolerant to various functional groups on heteroarenes and benzenes. Furthermore, this method can be applied to the synthesis of trimethylsilyl group-containing analogs of TAC-101, which is a bioactive synthetic retinoid with selective affinity for retinoic acid receptor α (RAR-α) binding. We also report further transformations of the silylated products into useful derivatives.
- Nozawa-Kumada, Kanako,Osawa, Sayuri,Sasaki, Midori,Chataigner, Isabelle,Shigeno, Masanori,Kondo, Yoshinori
-
p. 9487 - 9496
(2017/09/23)
-
- Nickel-Catalyzed C-H Silylation of Arenes with Vinylsilanes: Rapid and Reversible β-Si Elimination
-
The reaction of C6F5H and H2C=CHSiMe3 with catalytic [iPr2Im]Ni(2-H2C=CHSiMe3)2 (1b) exclusively forms the C-H silylation product C6F5SiMe3 with ethylene as a byproduct ([iPr2Im] = 1,3-di(isopropyl)imidazole-2-ylidene). Catalytic C-H bond silylation is facile with partially fluorinated aromatic substrates containing two ortho fluorine substituents adjacent to the C-H bond and 1,2,3,4-tetrafluorobenzene. Less fluorinated substrates react slower. Under the same reaction conditions, catalytic [IPr]Ni(η2-H2C=CHSiMe3)2 (1a) ([IPr] = 1,3-bis[2,6-diisopropylphenyl]-1,3-dihydro-2H-imidazol-2-ylidene) provided only the alkene hydroarylation product C6F5CH2CH2SiMe3. Mechanistic studies reveal that the C-H activation and β-Si elimination steps are reversible under catalytic conditions with both catalysts 1a and 1b. With catalytic 1a, reversible ethylene loss after β-Si elimination was also observed despite its inability to catalyze C-H silylation; the reductive elimination step to form the silylation product is much slower than reductive elimination to form the alkene hydroarylation product. Reversible ethylene loss was not observed with 1b, which suggests that the rate-limiting step in the reaction is neither C-H activation nor β-Si elimination but either ethylene loss or reductive elimination of cis-disposed aryl and SiMe3 moieties.
- Elsby, Matthew R.,Johnson, Samuel A.
-
supporting information
p. 9401 - 9407
(2017/07/22)
-
- Synthetic applications of fluorinated phenyllithiums: Preparation of fluorinated α-methylstyrenes, benzhydrols, benzophenones and aryltrimethylsilanes
-
Regioselective preparations of a number of fluorinated phenyllithiums have recently been reported, which in some cases also contain one or more bromine substituents. These have now been applied to the synthesis of the corresponding halogenated 2-arylpropenes (α-methyl-styrenes), benzhydrols, trifluoromethylbenzhydrols, benzophenones and aryltrimethylsilanes.
- Yarwood, Thomas David,Waring, Anthony John,Coe, Paul Leslie
-
p. 113 - 119
(2007/10/03)
-
- -
-
Functionalisation in 2 position of benzenes 1,3-disubstituted by para-directing groups has been investigated, involving 2-trimethylsilylated intermediates when the classical methods (particularly these involving the anion in 2 position) are ineffective. Thus 2-trimethylsilyl derivatives of 1,3-dihalo- or 1,3-dimethoxybenzene have been prepared in good yields. Their conversion into the corresponding 1,2,3-trisubstituted benzenes has been conveniently performed upon acetylation, iodination or sulfonation, except in the case of the sulfonation of the 1,3-dimethoxylated compound in which the ipso effect of the silyl group is surpassed by the directing effect of the methoxy substituents. In contrast, whith the same substrate, cyanation in position 2 was successfully carried out using chlorosulfonyl isocyanate: to our knowledge this reaction is the first example of substitution of a trimethylsilyl by a cyano group in the aromatic series.
- Bennetau, Bernard,Rajarison, Florent,Dunogues, Jacques,Babin, Pierre
-
p. 10843 - 10854
(2007/10/02)
-