Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Titanocene-Catalyzed Alkylation of Aryl-Substituted Alkenes with Alkyl Halides
Jun TeraoHiroyasu WatabeMasako MiyamotoNobuaki Kambe
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2003 Volume 76 Issue 11 Pages 2209-2214

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Abstract

Aryl-substituted alkenes (ArHC=CH2) react with alkyl halides (R–X, X = Br or Cl) in the presence of a catalytic amount of [Cp2TiCl2] and nBuMgCl 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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© 2003 The Chemical Society of Japan
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