Zr-Catalyzed Coupling Reaction of Alkyl Halides, Tosylates, and Sulfates with β-Phenethyl Grignard Reagents via Styrene-Zirconate Intermediates

Abstract

β-Phenethylmagnesium chlorides react with alkyl halides, tosylates, and sulfates in the presence of a catalytic amount of Cp₂ZrCl₂ to afford 2-arylalkanes via alkylation of styrene-zirconate intermediates at the benzylic position. Competitive reaction using mixtures of alkyl halides (alkyl-X; X = F, Cl, Br) showed that the reactivities of the halides increase in the order of alkyl-Cl < alkyl-F < alkyl-Br with the relative rates of 1:19:428.

Key words

zirconocene - β-phenethyl Grignard reagent - coupling reaction - alkyl halide - alkyl tosylate

References

• 1 Lipshutz BH. Sengupta S. In Organic Reactions   Vol. 41:  Joyce RM. John Wiley and Sons, Inc.; New York: 1992.  p.135 
• 2a Cárdenas DJ. Angew. Chem. Int. Ed.  1999,  38:  3018 
• 2b Luh T.-Y. Leung M.-K. Wong K.-T. Chem. Rev.  2000,  100:  3187 
• 2c Cárdenas DJ. Angew. Chem. Int. Ed.  2003,  42:  384 
• 2d Netherton MR. Fu GC. Adv. Synth. Catal.  2004,  346:  1525 
• 2e Terao J. Kambe N. J. Synth. Org. Chem. Jpn.  2004,  62:  1192 
• 2f Frisch AC. Beller M. Angew. Chem. Int. Ed.  2005,  44:  674 
• 3a Terao J. Watanabe T. Saito K. Kambe N. Sonoda N. Tetrahedron Lett.  1998,  39:  9201 
• 3b Armas J. Kolis SP. Hoveyda AH. J. Am. Chem. Soc.  2000,  122:  5977 
• 5 Nii S. Terao J. Kambe N. J. Org. Chem.  2000,  65:  5291 
• 4It is known that Ni-catalyzed cross-coupling reaction of aryl halides with isopropyl Grignand reagent affords n-propyl-benzene as the major product via isomerization of isopropyl group, see:
• 4 Kiso Y. Tamao K. Kumada K. J. Organomet. Chem.  1973,  50:  C12 
• Ni-catalyzed coupling reactions using alkyl fluorides, see:
• 6a Terao J. Ikumi A. Kuniyasu H. Kambe N. J. Am. Chem. Soc.  2003,  125:  5646 
• 6b Terao J. Todo H. Watanabe H. Kambe N. Angew. Chem. Int. Ed.  2004,  43:  6180 
• 6c Terao J. Watabe H. Kambe N. J. Am. Chem. Soc.  2005,  127:  3656 
• 7 As the similar pathways leading to 12, it has been proposed that zirconate complex [Cp₂ZrEt(CH₂=CH₂)MgBr] are formed by the reaction of Cp₂ZrCl₂ with 3 equiv of EtMgBr, see: Takahashi T. Suzuki N. Kageyama M. Nitto Y. Saburi M. Negishi E. Chem. Lett.  1991,  1579 
• 8 s-Butylbenzene was formed in 81% yield by the direct reaction of EtOTs with PhCHMeMgBr in THF for 5 min at 50 °C. This result indicates that α-substituted benzyl Grignard reagents readily react with alkyl electrophiles, see also: Terao J. Saito K. Nii S. Kambe N. Sonoda N. J. Am. Chem. Soc.  1998,  120:  11822 
• 9 Reactivities of alkyl groups on Zr as β-hydrogen donors, see: Negishi E. Nguyen T. Maye JP. Choueiri D. Suzuki N. Takahashi T. Chem. Lett.  1992,  2367 
• 10 Negishi E. Swanson DR. Takahashi T. Chem. Commun.  1990,  1254 
• 11 Ura Y. Hara R. Takahashi T. Chem. Commun.  2000,  875