Abstract
Palladium catalysed carbonylation reactions using the meta- and para-iodo derivatives of all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane (4) are illustrated as the start point for a variety of functional group interconversions. The resultant benzaldehyde and benzoic acids offer novel building blocks for further derivatisation and facilitate the incorporation of the facially polarised all-cis-1,2,4,5-tetrafluorocyclohexane motif into more advanced molecular scaffolds.
Highlights
Fluorinated building blocks have proven invaluable in drug discovery [1] and agrochemical research programmes [2]
In the case of the hexafluorocyclohexane, the ring maintains a chair conformation and there are three C–F bonds orientated triaxial, on one face of the ring. This gives rise to a large dipole moment (6.2 D) and a molecule which is among the most polar aliphatics known in organic chemistry
A key reaction for this programme involved the carbonylation of aryl iodides 5, 6 and 7 which are derived by HIO4 treatment of all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane (4)
Summary
Fluorinated building blocks have proven invaluable in drug discovery [1] and agrochemical research programmes [2]. The all-cistetrafluorocyclohexanes 2 and 3 are facially polarised because in the chair conformation, they always have two 1,3diaxial C–F bonds on one face of the ring, and this results in ring systems with large dipole moments (4.9 D for 2 and 5.2 D for 3). Compounds 1–3 are unfunctionalised and not amenable to derivatisation, and we started to explore the chemistry of all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane (4) [6], to access derivatives carrying this ring motif. In this paper it is demonstrated that palladium mediated carbonylation of the aryl iodinated derivatives 5–7 forms the basis of a diversity of new products which may prove attractive as building blocks for structure activity studies in bioactive research projects.
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