- Palladium Catalyzed Monoselective α-Arylation of Sulfones and Sulfonamides with 2,2,6,6-Tetramethylpiperidine·ZnCl·LiCl Base and Aryl Bromides
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A palladium catalyzed Negishi-type α-arylation of sulfones and sulfonamides with a broad range of aryl bromides has been developed. The substrates are selectively metalated in situ with tmp·ZnCl·LiCl base (tmp: 2,2,6,6-tetramethylpiperidine) and cross-coupled in the presence of a catalyst system that is generated from Pd(dba)2 and XPhos. Electron-deficient, electron-rich, and heterocyclic aryl bromides have been successfully cross-coupled, and sensitive functional groups are well tolerated. Simple aryl bromides are converted overnight at 60 °C in THF while heteroaryl bromides are efficiently coupled within 2 h at 130 °C in a microwave reactor. The desired monoarylated α-branched benzyl sulfones and sulfonamides were obtained in good yields, and overarylation was not detected. The procedure is ideal for late stage functionalization in parallel medicinal chemistry.
- Knauber, Thomas,Tucker, Joseph
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p. 5636 - 5648
(2016/07/14)
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- Catalyst-controlled divergence in cycloisomerisation reactions of N-propargyl-N-vinyl sulfonamides: Gold-catalysed synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines
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Gold-catalysed, divergent synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines from N-propargyl-N-vinyl sulfonamides has been achieved. Echavarren's gold(i) catalyst promoted the formation of pyrrole derivatives whereas the combination of PPh3AuCl and AgSbF6 afforded dihydropyridines. The aza-enyne precursors for the cycloisomerisation reaction were prepared by a base-mediated formal vinylic substitution reaction of 2-bromoallyl sulfones.
- Undeela, Sridhar,Thadkapally, Srinivas,Nanubolu, Jagadeesh Babu,Singarapu, Kiran Kumar,Menon, Rajeev S.
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supporting information
p. 13748 - 13751
(2015/09/07)
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- Modifiable sulfur tethers as directing groups for aromatic C-H acetoxylation reactions
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A designed new class of modifiable sulfur tethers for aromatic C-H bond functionalizations is presented. As a model, the palladium-catalyzed directed acetoxylation reaction was studied. The more challenging sulfoxide tethers were the most effective in this transformation, showing a broad functionality tolerance, high S oxido-redox stability and no catalyst poisoning. Preliminary mechanistic studies indicate that the higher reactivity and selectivity shown by the sulfoxide tethers vs. the corresponding sulfones can be attributed to an extra coordination of the sulfoxide S atom to the catalyst. The utility of the presented methodology to generate structurally interesting aromatic derivatives by a subsequent modification of the S-tether is also exemplified.
- Richter, Heinrich,Beckendorf, Stephan,Mancheno, Olga Garcia
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supporting information; experimental part
p. 295 - 302
(2011/04/16)
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- THERMOLYSIS OF SODIUM SALTS OF TOSYLHYDRAZONES OF SOME HETEROCYCLIC ALDEHYDES IN THE PRESENCE OF SILVER CHROMATE: 1,3 NC MIGRATION OF TOSYL GROUP
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The thermal decompositions of sodium salts of tosylhydrazones of furfural, thiophene-2-aldehyde, 1-methylpyrrole-2-aldehyde, and pyridine-2-aldehyde in the presence of silver chromate gave 2-furyl(p-toluenesulfonyl)methane, thiophene-2-(p-toluenesulfonyl)methane, 1-methylpyrrole-2-(p-toluenesulfonyl)methane, and pyridine-2-(p-toluenesulfonyl)methane, respectively, via 1,3 NC migration of tosyl group.The same type of reactions with sodium salts of tosylhydrazones of thiophene-3-aldehyde, pyridine-3-aldehyde, and pyridine-4-aldehyde also afforded the corresponding p-toluenesulfonylmethanes but the yields were slightly lower comparing to the above cases.
- Saito, Katsuhiro,Ishihara, Hiraku
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p. 1891 - 1898
(2007/10/02)
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