Tetrahedron p. 991 - 997 (1983)
Update date:2022-08-16
Topics:
Demuth, Martin
Mikhail, Gamal
Electrophile-mediated cyclopropane cleavage in tricyclo<3.3.0.02,8>octan-3-one (1a) is increasingly directed towards the maximum bond overlap site in the following order of reagents: acetyl methanesulfonate, +Br(1-) or I(1-); t-butyl-dimethylsilyl iodide; t-butyldimethylsilyl trifluoroacetate; trimethylsilyl trifluoroacetate.The latter reagent gives rise to one single regioisomer (->6a).Routine yields of isolated products lie between 78 and 87percent.Increasing regioselectivity is governed by increasing electrophilic power and lowered nucleophilic strength of the reagents.Independent of these two factors, a C(4)-exo substituent in 1 directs the opening modes undirectionally (->2b, 6b).Irrespective of the substitution pattern at C(4) (1a-d), the cyclopropane moiety rearranges smoothly to olefinic ketones (8a-d) when the polymer-supported triflate analog Nafion-TMS is used in toluene at 80 deg C.The reaction proceeds via intramolecular proton (deuterion) abstraction by the transient electron-rich enoxy double bond.This is the first fully proved case of such an intramolecular process.Aro-semibullvalenes (18,22) similarly rearrange to aro-semibarrelenes (e.g. 21, 23) in the presence of Nafion-TMS.The latter rearrangement also takes place at room temperature when 18 or 22 are treated with commercial tetramethylsilane (TMS) and a catalytic amount of trifluoroacetic acid.An unknown impurity in the TMS reacts with the acid to form a powerful electrophilic composition.A cheap and convenient in situ preparation of TMS-triflate is described by mixing trifluoromethanesulfonic acid and TMS at room temperature.
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Doi:10.1016/S0040-4039(01)87697-8
(1969)Doi:10.1002/cmdc.201800178
(2018)Doi:10.1016/j.bmcl.2017.07.057
(2017)Doi:10.1016/j.ejmech.2020.112113
(2020)Doi:10.1063/1.442252
(1981)Doi:10.1021/ja00395a051
(1981)