Carbenoid insertions and cyclometallations of zirconacycles

Abstract

The synthesis of zirconacycles and further elaborations to produce a wide variety of
carbocyclic and heterocyclic systems is well established. This thesis focuses on the
insertion of chloro(aryl)methyllithiums (benzyl carbenoids) into a range of
zirconacyclopentenes and zirconacyclopentanes.

Benzyl carbenoid insertion into a zirconacyclopentene generated the
zirconacyclohexene via a 1,2-metalate rearrangement. A low temperature quench
afforded the expected benzyl inserted product. Quenching at higher temperatures
afforded a styrene containing product. It was proposed that the styrene product was
formed via a novel endocyclic cyclometallation to afford a zirconocene n2-alkene
complex followed by decomplexation. A wide variety of zirconacyclopentenes and
benzyl carbenoids have been investigated.

A range of benzyl carbenoids were inserted into a zirconacyclopentane to afford the
expected benzyl inserted product. Double benzyl carbenoid insertion was also observed
and afforded a mono-alkene product. It was speculated that the bis-inserted products
were formed via a zirconacycloheptane followed by a novel endocyclic
cyclometallation.

Having shown that zirconacyclohexenes underwent an endocyclic cyclometallation to
afford a zirconocene n2-alkene complex, the concept of intramolecular trapping of the
zirconocene n2-alkene complex, to generated bicyclic compounds, was investigated.

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Identifiers

ORCID for Richard J. Whitby: orcid.org/0000-0002-9891-5502

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