Titanocene-Catalyzed Alkylation of Aryl-Substituted Alkenes with Alkyl Halides

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作者：

机构：

[1] Terao, Jun

[2] Watabe, Hiroyasu

[3] Miyamoto, Masako

[4] Kambe, Nobuaki

来源：

Kambe, N. (kambe@chem.eng.osaka-u.ac.jp) | 1600年 / Chemical Society of Japan卷 / 76期

关键词：

Alkylation - Benzene - Bromine compounds - Catalysis - Chemical bonds - Dimerization - Free radicals - Stereochemistry - Substitution reactions;

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摘要：

Aryl-substituted alkenes (ArHC=CH2) react with alkyl halides (R-X, X = Br or Cl) in the presence of a catalytic amount of [Cp 2TiCl2] and BuMgCl in Et2O to give alkylated alkenes (ArHC=CHR). This reaction proceeds regio- and stereoselectively under mild conditions to afford E-olefins. Primary and secondary alkyl bromides and secondary alkyl chlorides can be used as suitable alkylating reagents. The reactions of aliphatic alkenes, such as 1-octene and internal alkenes, were sluggish. When t-alkyl halides are employed, alkylative dimerization of alkenes proceeds exclusively to give symmetrical vic-diarylalkanes. These reactions involve addition of alkyl radicals to arylalkenes to form benzyl radicals as a carbon-carbon bond-forming step. Dimerization of thus formed benzyl radicals affords symmetrical alkanes and β-hydrogen elimination from benzyltitanocene intermediates gives alkylated alkenes. A possibility that titanocene activates alkenes as radical accepters was also proposed.

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