Document Detail


Mechanism and Origins of Ligand-Controlled Selectivities in [Ni(NHC)]-Catalyzed Intramolecular (5+2) Cycloadditions and Homo-Ene Reactions: A Theoretical Study.
MedLine Citation:
PMID:  23273283     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The mechanism and origins of selectivities in [Ni(NHC)]-catalyzed intramolecular (5+2) cycloadditions and homo-ene reactions of vinylcyclopropanes (VCPs) and alkynes have been studied using density functional theory. The preferred mechanism involves oxidative alkyne-alkene cyclization to form a metallacyclopentene intermediate, in contrast to cyclopropane cleavage pathway in the reaction with Rh(I) catalysts. The selectivity between the (5+2) and homo-ene products is determined in the subsequent competing reductive elimination and β-hydride elimination steps. Two similar-sized N-heterocyclic carbene (NHC) ligands, SIPr and ItBu yielded reversed product selectivity, favoring the (5+2) and homo-ene products respectively. This is attributed to the anisotropic steric environment of these NHC ligands, which position the bulky substituents on the ligand to different directions and leads to distinct steric control in the reductive elimination and β-hydride elimination transition states.
Authors:
Xin Hong; Peng Liu; K N Houk
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-31
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  -     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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