Subscribe to RSS
DOI: 10.1055/s-0030-1258723
Pd-Catalyzed γ-Arylation of α,β-Unsaturated Esters from Silyl Ketene Acetals
Contributor(s):Paul Knochel, Andreas J. WagnerUniversity of Illinois at Urbana-Champaign, USA
Palladium-Catalyzed γ-Arylation of α,β-Unsaturated Esters from Silyl Ketene Acetals
Angew. Chem. Int. Ed. 2010, 49: 5757-5761
Publication History
Publication Date:
21 October 2010 (online)
Key words
α,β-unsaturated esters - silyl ketene acetals - palladium
Significance
Herein, a new γ-selective arylation of α,β-unsaturated esters is reported by coupling aryl, heteroaryl or vinyl halides with the corrsponding silicon dienolates. The procedure tolerates reactive functional groups and proceeds in high yields even for sterically challenging substrates. The products are valuable compounds only available in multi-step sequences by conventional methods.
Comment
Interestingly, the typical fluoride additives usually used to activate silicon enolates are not required for this reaction. The triethylsilyl substituent (TES) has been found to be better suited than TMS or TBS groups. When the ZnCl2 additive is used in only catalytic amounts, similar yields can be obtained compared to stoichiometric use. However, the reaction time increases approximately six-fold. It should also be noted that, while aryl chlorides typically do not react, the corresponding iodides tend to react in poor yields.