The cyclopropyl effect on the regioselectivity of coupling reactions involving the lithiation of 1-cyclopropyl-2-arylacetylenes
摘要:
The cyclopropyl effect controlled the regioselectivity of the cross coupling reactions of propargylic/allenylic metallic species with electrophiles affording alkynic cycloproparies. It was proposed that the strain in cyclopropyl ring, which makes the formation of vinylidenecyclopropanes unfavorable, determined the regioselectivity. Control experiment of i-propyl, cyclobutyl, and cyclohexylphenylacetylenes were conducted to support the above speculation. (c) 2006 Elsevier Ltd. All rights reserved.
Generation of Allenic/Propargylic Zirconium Complexes and Subsequent Cross-Coupling Reactions: A Facile Synthesis of Multisubstituted Allenes
作者:Hao Zhang、Xiaoping Fu、Jingjin Chen、Erjuan Wang、Yuanhong Liu、Yuxue Li
DOI:10.1021/jo9020419
日期:2009.12.18
The β-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