- Ruphos-mediated Suzuki cross-coupling of secondary alkyl trifluoroborates
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A Ruphos-mediated Suzuki cross-coupling between (hetero)aryl bromides and secondary alkyltrifluoroborates is described using palladium catalysis. The Ruphos ligand showed superior properties as compared to S-Phos in this type of reaction. This method constitutes a valuable extension to current methods for the straightforward production of secondary-alkylated (hetero)aryl derivatives.
- van den Hoogenband, Adri,Lange, Jos H.M.,Terpstra, Jan Willem,Koch, Melle,Visser, Gerben M.,Visser, Martin,Korstanje, Ties J.,Jastrzebski, Johann T.B.H.
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p. 4122 - 4124
(2008/09/21)
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- Friedel-crafts benzoylation of alkylbenzenes with brazoic anhydride catalyzed by solid superacids
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The liquid-solid phase benzoylation of mono-alkylbenzenes with methyl, ethyl, propyl, and butyl groups and xylenes was carried out with benzoic anhydride at 100-110°C over solid superacids: SO4/ZrO 2, WO3/ZrO2, and SO4/ HfO 2. The reactivity ratio obtained by the competitive method of reaction over WO3/ZrO2 was 1 to 4.6 for toluene to p-xylene and 1.1:10:1 among o-, m-, and p-xylenes, respectively. Although the SO4/ZrO2 catalyst gave high yields of 92 and 97% for toluene and ethylbenzene in a 3:7 distribution of o- and p-isomers, respectively, low yields were observed with propyl and butylbenzenes over the catalyst: that is, 5 and 2% for propylbenzene and isopropylbenzene, 14% for isobutylbenzene, and trace yields for butylbenzene, s-butylbenzene, and t-butylbenzene, respectively. The usual Friedel-Crafts benzoylation using AlCl3 was examined in the present alkylbenzenes in order to confirm the low reactivity of both propyl and butylbenzenes. The results were similar to those with the SO4/ZrO2 catalyst; that is, the yields at 0°C for 1 h were 37, 21, 6, 1, 0, 3, and 2% for toluene, ethylbenzene, propylbenzene, isopropylbenzene, butylbenzene, s-butylbenzene, and t-butylbenzene, respectively, showing an unexpected result where there was no distinction between homogeneous and heterogeneous conditions.
- Nakamura, Hideo,Arata, Kazushi
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p. 1893 - 1896
(2007/10/03)
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- A comparative product investigation between Grignard reactions of benzophenone and coupling reactions of electrogenerated benzophenone radical anions and alkyl radicals in THF
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The 1,6-to 1,2-addition product ratios of the Grignard reactions of benzophenone with t-, s- and n-C4H9MgCl have been compared with the corresponding ratios obtained by the electrolysis of benzophenone in presence of t-, s- and n-C4H9S+(CH3)2, ClO4-in THF. The Grignard reaction ratios 0.81, 0.50 and 0.19, respectively, were obtained whereas the corresponding electrolysis ratios were 2.26, 1.23 and 1.61. From this comparison of product ratios it is concluded that none of the Grignard reactions of benzophenone proceeds through a complete free coupling process of benzophenone radical anions and butyl radicals. The ET character of the Grignard reactions of benzophenone with t-, s- and n-C4H9MgCl was estimated to be 65, 61 and 26%, respectively.
- Lund, Torben,Ohlrich, Ditte,Borling, Pernille
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p. 932 - 937
(2007/10/03)
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