Jump to main content
Jump to site search

Issue 30, 2011
Previous Article Next Article

Cyclisation of α,ω-dienes promoted by bis(indenyl)zirconium sandwich and ansa-titanocene dinitrogen complexes

Author affiliations

Abstract

Metallation of a variety of α,ω-dienes has been explored with an η95-bis(indenyl)zirconium sandwich compound and an ansa-titanocene dinitrogen complex. The η95-bis(indenyl)zirconium sandwich compound, 9-C9H5-1,3-Pr2)(η5-C9H5-1,3-iPr2)Zr, served as an isolable source of Negishi's reagent and readily formed a kinetic mixture of cis and trans diastereomers of the corresponding zirconacyclopentanes upon diene metallation. For pure hydrocarbon substrates such as 1,6-heptadiene and 1,7-octadiene, an equimolar amount of cis and trans diastereomers were the kinetic products; isomerization to the thermodynamically favoured trans isomers was observed over time at ambient temperature or upon heating to 105 °C, respectively. By contrast, substitution of the methylene or ethylene spacer in the α, ω-diene with a fluorenyl group (e.g. 9,9-diallylfluorene) resulted in exclusive kinetic formation of the trans diastereomer. Amino-substituted dienes were also readily cyclised and one example was characterised by single-crystal X-ray diffraction. Similar studies were also conducted with the ansa-titanocene dinitrogen complex, [Me2Si(η5-C5Me4)(η5-C5H3-3-tBu)Ti]2211-N2), and both kinetic and thermodynamic selectivities evaluated. The use of a C1 symmetric ansa-metallocene increases the number of isomeric possibilities. For diallyl tert-butyl amine, diene metallation was more selective than for the bis(indenyl)zirconium sandwich compound and isomerization was also more rapid. Preliminary functionalisation reactivity for both the zircona- and titanocycles was also explored.

Graphical abstract: Cyclisation of α,ω-dienes promoted by bis(indenyl)zirconium sandwich and ansa-titanocene dinitrogen complexes

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 26 Jan 2011, accepted on 25 Mar 2011 and first published on 13 May 2011


Article type: Paper
DOI: 10.1039/C1DT10149H
Citation: Dalton Trans., 2011,40, 7737-7747
  •   Request permissions

    Cyclisation of α,ω-dienes promoted by bis(indenyl)zirconium sandwich and ansa-titanocene dinitrogen complexes

    D. Pun, D. J. Knobloch, E. Lobkovsky and P. J. Chirik, Dalton Trans., 2011, 40, 7737
    DOI: 10.1039/C1DT10149H

Search articles by author