- Site-Selective C?H Oxygenation via Aryl Sulfonium Salts
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Herein, we report a two-step process forming arene C?O bonds in excellent site-selectivity at a late-stage. The C?O bond formation is achieved by selective introduction of a thianthrenium group, which is then converted into C?O bonds using photoredox chemistry. Electron-rich, -poor and -neutral arenes as well as complex drug-like small molecules are successfully transformed into both phenols and various ethers. The sequence differs conceptually from all previous arene oxygenation reactions in that oxygen functionality can be incorporated into complex small molecules at a late stage site-selectively, which has not been shown via aryl halides.
- Sang, Ruocheng,Korkis, Stamatis E.,Su, Wanqi,Ye, Fei,Engl, Pascal S.,Berger, Florian,Ritter, Tobias
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supporting information
p. 16161 - 16166
(2019/11/03)
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- Organocatalytic selective benzoylation of alcohols with trichloromethyl phenyl ketone: Inverse selectivity in benzoylation of alcohols containing phenol or aromatic amine functionality
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Trichloromethyl phenyl ketone benzoylates primary and secondary aliphatic alcoholic groups in compounds also containing a phenolic group in the presence of 2-10 mol % of PMDETA organocatalyst at room temperature in high yields and excellent selectivity. It also shows the potential to selectively benzoylate primary alcoholic groups of aminoarylalkanols and primary-secondary diols as well as primary amino group of alkyl amines in the presence of aryl amines under similar conditions. A rationale for the selectivity and efficiency of the reaction has been provided.
- Ram, Ram N.,Soni, Vineet Kumar,Gupta, Dharmendra Kumar
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p. 9068 - 9075
(2012/11/07)
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- A mild, efficient and selective deprotection of t-butyldimethylsilyl-protected phenols using cesium carbonate
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A mild and efficient method for the deprotection of aryl t-butyldimethysilyl (TBS) ethers is described. The protecting group TBS could be cleaved from aryl silyl ethers using cesium carbonate in DMF-H2O at room temperature to give the corresponding phenols in excellent yields. The reaction conditions allowed selective deprotection of aryl TBS-protected phenols in the presence of TBS, phenyloxycarbonyl or tetrahydropyranyl-protected alcohols.
- Jiang, Zhi-Yong,Wang, Yan-Guang
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p. 3859 - 3861
(2007/10/03)
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- Influence of hydrogen bonding in the activation of nucleophiles: PhSH- (catalytic) KF in N-methyl-2-pyrrolidone as an efficient protocol for selective cleavage of alkyl/aryl esters and aryl alkyl ethers under nonhydrolytic and neutral conditions
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The nucleophilicity of arenethiols can be augmented via hydrogen bonding with 'naked' halide anion. The activity of the halide anions follow the order F- ?Cl- ~ Br- ~ I- and is dependent on the countercation (Bu4N ~ Cs ~ K > Na ?Li). The solvent plays an important role in nucleophilic activation as well as regeneration of the effective nucleophile (e.g. ArS-) and those with high dielectric constant, high molecular polarizability, high donor number (DN), and low acceptor number (AN) are the most effective. Selective deprotection of alkyl/aryl esters and aryl alkyl ethers can be achieved under nonhydrolytic and neutral conditions by the treatment with thiophenol in 1-methyl-2-pyrrolidone (NMP) in the presence of a catalytic amount of KF. Aryl esters are selectively deprotected in the presence of alkyl esters and alkyl methyl ethers during intramolecular competitions.
- Chakraborti, Asit K.,Sharma, Lalima,Nayak, Mrinal K.
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p. 2541 - 2547
(2007/10/03)
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- Selective sulfonylation of arenes and benzoylation of alcohols using lithium perchlorate as a catalyst under neutral conditions
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Sulfonylation of aromatics with p-toluenesulfonyl chloride and benzoylation of alcohols with benzoyl chloride using lithium perchlorate as a catalyst is described. The remarkable selectivity under neutral conditions is an attractive feature of this method.
- Bandgar,Kamble,Sadavarte,Uppalla
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p. 735 - 738
(2007/10/03)
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- 1-(2,5-dichlorophenyl)-2,2-bis(methylsulfanyl)vinyl esters as highly efficient chemoselective acylating reagents
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1-(2,5-Dichlorophenyl)-2,2-bis(methylsulfanyl)vinyl esters 4f-k were prepared in yields usually greater than 90%, by reacting acyl chlorides with 1-(2,5-dichlorophenyl)-2,2-bis(methylsulfanyl)ethanone enolate. These esters were demonstrated to be excellent chemoselective reagents for the acylation of amines, alcohols, thiols, pyrrole and indole. From all the acylation reactions the dimethyl α-oxo dithioacetal 2d, recyclable for the preparation of esters 4f-k, could be recovered in 90-100% yield.
- Degani,Dughera,Fochi,Serra
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p. 1200 - 1208
(2007/10/03)
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- PROTECTION DES PHENOLS PAR LE GROUPEMENT AZIDOMETHYLENE APPLICATION A LA SYNTHESE DE PHENOLS INSTABLES
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Phenols are protected by the azidomethylene group in basic, nucleophilic, oxidative, weakly reductive and weakly acidic media.This group is obtained by the reaction of sodium azide with aryloxymethyl chlorides.Its utility lies in the ease with which it can be removed under very mild conditions which allows the synthesis of very unstable phenolic compounds.
- Loubinoux, Bernard,Tabbache, Samir,Gerardin, Philippe,Miazimbakana, Joseph
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p. 6055 - 6064
(2007/10/02)
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