Hydrogen abstraction from spiro[2.n]alkanes

Charles Roberts, John C. Walton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

Hydrogen abstraction from spiro[2.3]hexane by t-butoxyl radicals gave spiro[2.3]hex-2-yl radicals; their rearrangement to cyclobutenylethyl radicals was followed by kinetic e.s.r. spectroscopy. Hydrogen abstraction at the methylene groups adjacent to the cyclopropyl rings [cyclopropylmethyl (cpm) sites] in higher spiro[2.n]alkanes gave spiro[2.n]alk-2-yl radicals, which rearranged to cycloalkenylethyl radicals too rapidly for detection, together with secondary radicals from abstraction at the other methylene groups in the larger ring. From the measured concentrations of the cycloalkenylethyl and secondary radicals the rate of hydrogen abstraction at the cpm sites relative to the rate of hydrogen abstraction at the secondary sites was determined; significant activation of the cpm hydrogens was found. This activation was attributed to a pseudo-allyl type of effect, i.e., to delocalisation of the unpaired electron into the Walsh orbitale of the cyclopropane ring of the spiro[2.n]alk-2-yl radicals; semi-empirical SCF-MO calculations supported this explanation. Photobromination of spiro[2.3]hexane occurred mainly by S H2 attack of bromine atoms at the cyclopropane methylene carbons with fission of either C-C bond.

Original languageEnglish
Pages (from-to)841-846
Number of pages6
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number6
Publication statusPublished - 1 Dec 1985

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