Room temperature observation of p-xylylenes by 1H NMR and evidence for diradical intermediates in their oligomerization

Walter S Trahanovsky; Steven P Lorimor

doi:10.1021/jo0516279

Room temperature observation of p-xylylenes by 1H NMR and evidence for diradical intermediates in their oligomerization

J Org Chem. 2006 Mar 3;71(5):1784-94. doi: 10.1021/jo0516279.

Authors

Walter S Trahanovsky¹, Steven P Lorimor

Affiliation

¹ Department of Chemistry, Iowa State University and Ames Laboratory, Ames, Iowa 50011-3111, USA. wtrahan@iastate.edu

PMID: 16496962
DOI: 10.1021/jo0516279

Abstract

p-Quinodimethanes (p-QDMs) are reactive molecules that have been invoked as transient intermediates in a number of reactions. Dilute solutions of benzene-based p-QDMs, p-xylylene (1), alpha-methyl-p-xylylene (10), and 2,5-dimethyl-p-xylylene (11) can be prepared by fluoride-induced elimination of trimethylsilyl acetate from the appropriate precursor. It has been found that these solutions are stable enough to allow these reactive p-QDMs to be observed by 1H NMR spectroscopy at room temperature. For the first time, the 13C NMR spectrum of p-QDM 1 was observed. After several hours at room temperature, these p-QDMs form dimers, trimers, and insoluble oligomers. Formation of trimers provides evidence that p-QDMs 1, 10, and 11 dimerize by a stepwise mechanism involving dimeric diradicals as intermediates.