Bromine-Lithium Exchange in 1,2-Dibromobenzene and the Intermediacy of 1,2-Dilithiobenzene

Matthias Filthaus ,  Holger F. Bettinger 

Ruhr Universität Bochum Organische Chemie II, Universitätsstr. 150, Bochum 44780, Germany

Abstract

Halogen-metal exchange in ortho-dibromobenzene 1 using four equivalents of tert-butyl lithium (t-BuLi) in Et2O:THF (1:1) at -120° C was observed to yield ortho-difunctionalized benzenes 2 after quenching with an excess of electrophiles based on analysis by GC/MS.

Two reaction pathways are conceivable. The thermally unstable ortho-lithiobromobenzene 3 formed in the first exchange step could again be lithiated to give ortho-dilithiobenzene 4 (path A). Our trapping studies with electrophiles of differing reactivities show that a successive exchange-functionalisation mechanism (path B) through 5 and 6 is operating.

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Presentation: poster at 18th Conference on Physical Organic Chemistry, Posters, by Matthias Filthaus
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-31 15:02
Revised:   2009-06-07 00:44
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