Generation of allenic/propargylic zirconium complexes and subsequent cross-coupling reactions: a facile synthesis of multisubstituted allenes.
The beta-alkoxide elimination reaction of propargylic ether with Negishi reagent leads to allenes and/or alkynes after hydrolysis. The product distribution is highly dependent on the substitution pattern of starting propargylic ethers; that is, aryl- or alkyl-substituted propargylic ethers favor the allene products, whereas TMS-substituted propargylic ethers afford alkynes. DFT calculations revealed that both the large steric effect and the beta-effect of the TMS group favor the alkyne products, reversing the selectivity. Subsequent coupling reactions of the allenic/propargylic zirconium intermediates with aryl iodides in the presence of Pd(PPh(3))(4)/CuCl provide a straightforward route for the synthesis of multisubstituted allenes.
Zhang
Hao
H
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, People's Republic of China.
Fu
Xiaoping
X
Chen
Jingjin
J
Wang
Erjuan
E
Liu
Yuanhong
Y
Li
Yuxue
Y