Subscribe to RSS
DOI: 10.1055/s-2007-992479
Carboannulation of o-Bromobenzyl Zinc Bromide with Alkenes and Alkynes
Contributor(s):Paul Knochel, Andrei GavryushinTianjin University, P. R. of China
Nickel-Catalyzed Carboannulation Reaction of o-Bromobenzyl Zinc Bromide with Unsaturated Compounds
Org. Lett. 2007, 9: 5207-5210
Publication History
Publication Date:
23 January 2008 (online)
Key words
carboannulation - benzyl zinc halides - nickel catalysis
Significance
Indene and indane scaffolds are present in many biologically active compounds. Indene is also an important motif in modern catalysts for selective olefin polymerization. This reaction gives an operationally simple one-step method for the regioselective preparation of indenes and indanes from readily available starting materials. The use of TMS alkynes, followed by the removal of the TMS group by CF3CO2H provides a general method for the preparation of both 1- and 2-substituted indenes from the same alkyne.
Comment
An intramolecular variant of the Negishi coupling has almost never been used in synthetic chemistry. This carboannulation process is relatively regioselective, being governed by both steric and electronic effects. Interestingly, the electronic effects are opposite for the formation of indenes and indanes, as shown by the preparation of molecules bearing a -CO2Me group. The reaction mechanism has not been confirmed, but supposedly involves the formation of annulated nickelacyclobutane species.