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Reaktionen Pentafluorethyl‐substituierter Bicyclo[2.1.1]hexan‐Derivate
Author(s) -
Kirmse Wolfgang,
Wonner Aribert
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931260218
Subject(s) - chemistry , solvolysis , bicyclic molecule , carbocation , trifluoroacetic acid , medicinal chemistry , trifluoromethanesulfonate , sulfonate , bromide , stereochemistry , organic chemistry , hydrolysis , catalysis , sodium
Reactions of Pentafluoroethyl‐Substituted Bicyclo[2.1.1]hexane Derivatives The effect of inductively electron‐withdrawing substituents on the generation of 2‐bicyclo[2.1.1]hexyl cations was probed by means of pentafluoroethyl groups. 2‐Pentafluoroethyl‐2‐bicyclo[2.1.1]hexyl brosylate ( 4a ) and triflate ( 4b ) were found to rearrange with formation of the analogous 1‐pentafluoroethyl‐2‐bicyclo[2.1.1]hexyl sulfonates 5a, b . Solvolytic displacement did not compete with the rearrangement but occurred on 5b at elevated temperatures. Deuterium labels revealed that the rearrangement proceeded stereospecifically, with the sulfonate departing and rebonding on the same side of the molecular plane. Complete inversion was observed during solvolysis of 5b in aqueous dioxane while some retention (16%) occurred in trifluoroacetic acid. Predominant inversion even with the analogous diazonium ion in water attests to the reluctant formation of 1‐pentafluoroethyl‐2‐bicyclo[2.1.1]hexyl cations. Solvolysis rates of 4a, b and 5b were in close agreement with those of the analogous cyano derivatives, thus confirming that the resonance interaction of α1‐cyano groups with carbocations is small.