A novel route to fluoroarenes from trifluoroethanol

This Thesis describes the preparation of fluoroarenes using a palladium-catalysed coupling/electrocyclisation methodology. Difluoroenolzinc coupling partners, 1-(N,N-diethylcarbamoyloxy)-2,2-difluoro-1-zinc chloride and 2,2-difluoro-1-(2'-methoxy-ethoxymethoxy)-1-zinc chloride were prepared from trifluoroethanol at near ambient temperature and underwent Negishi coupling with a range of aryl-halides. A co-solvent (N,N-dimethylpropylene urea) was necessary to generate 2,2-difluoro-1-(2'-methoxy-ethoxymethoxy)-1-zinc chloride in good yield. The zinc coupling partners were also converted to (iodo)difluoroenols which participated in Suzuki-Miyaura coupling with a range of aryl-boronic acids and potassium aryl-trifluoroborates. Side reactions of the Suzuki-Miyaura couplings were circumvented by using tertiary butanol as the reaction solvent. Low temperature preparation of trifluoroborate coupling partners, potassium 2,2-difluoro-1-(N,N-diethylcarbamoyloxy)ethenyl trifluoroborate and potassium 2,2-difluoro-1-(2'-methoxy-ethoxymethoxy)ethenyl trifluoroborate, from trifluoroethanol was also accomplished. The trifluoroborates underwent Suzuki-Miyaura coupling with a range of aryl-halides. This Suzuki-Miyaura coupling protocol was used to prepare a range of fluorinated electrocyclisation precursors in modest to good yield. Subsequent electrocyclisation afforded fluorobenzene, fluoronaphthalene and fluorophenanthrene species. The electrocyclisations were investigated computationally in an attempt to rationalise the ease/difficulty of cyclisation.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2014

Author dc:creator

• Wilson, Peter

DOI

10.48730/0xk1-ck07

Identifier

T13938

OAI identifier oai:identifier

oai:strathclyde:7s75dc423