This paper reports the preparation of methyl substituted all-cis tetrafluorocyclohexanes prepared from a Birch reduction of benzoic acid, worked up with a methyl iodide quench. The resultant methylcyclohexadiene carboxylic acid was reduced to the alcohol, protected as an ether and then a sequence of functional group manipulations carried out to introduce four fluorines. The cyclohexadienyl ring was then epoxidised and the C-O bonds sequentially converted through deoxyfluorination reactions to two sets of isomers of all-cis tetrafluorocyclohexane isomers. The blocking methyl group renders the ring safe to hydrogen fluoride elimination. Deprotection of the benzylic ether and then oxidation gave aldehydes which were then used in Ugi and Passerini multicomponent reactions, allowing this facially polarised cyclohexane to be incorporated into peptidic structural motifs.
A study focused on the synthesis of a derivative of all-cis phenyl-2,3,5,6-tetrafluorocyclohexane, incorporating a methyl group at the benzylic position, found that the fluorination reactions of diepoxide and diol precursors, were susceptible to rearrangement and unexpected products. The origin of these rearranged products can be rationalised by aryl migrations occurring via phenonium ion intermediates, in adventitious pathways occurring during deoxofluorination reactions with hydrogen fluoride reagents.We dedicate this paper to Professor Veronique Gouverneur in recognition of her 2015 ACS Award for Creative work in Fluorine Chemistry.
Wird 2,5‐Bis‐diäthylaminomethyl‐hydrochinon (I) mit Triäthylphosphit (II) in Xylol 4 Stdn. auf 145‐150°C erhitzt, so entsteht unter Abspaltung von Diäthyl= amin das Diphospha‐Derivat (III).
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