‘Aromatic ring umpolung’, a rapid access to the main core of several natural products
作者:Kimiaka C. Guérard、Cyrille Sabot、Marc-André Beaulieu、Marc-André Giroux、Sylvain Canesi
DOI:10.1016/j.tet.2010.03.096
日期:2010.7
substituted phenols in the presence of (diacetoxyiodo)benzene promotes the formation of a phenoxenium ion, a very electrophilic species able to react with various nucleophiles leading rapidly to a plethora of different cores present in natural products via several novel oxidative processes. This strategy fits within the concept of ‘aromatic ring umpolung’; in this paper a personal account by our laboratory
An oxidative allylation process mediated by a hypervalent iodine reagent has been performed on polysubstituted phenols. This reaction, occurring in useful to good yields, leads to a rapid access to dienones containing a quaternary carbon center.
ortho‐selective nucleophilicaddition reaction of amines to 3‐substituted benzynes has been achieved. Despite a large trimethylsilyl substituent, primary amines attack the C2 position of 3‐silylbenzynes to produce 2‐silylanilines (see scheme). This outcome is likely to result from the inductive electron‐donating effect of the silyl group, which overrides its steric repulsion with the approaching amines.
Regioselective and stereoselective cyclizations of cyclohexadienones tethered to active methylene groups
作者:Rodolfo Tello-Aburto、Kyle A. Kalstabakken、Kelly A. Volp、Andrew M. Harned
DOI:10.1039/c1ob06125a
日期:——
of 2,5-cyclohexadienones tethered to activated methylene groups was studied. The substitution around the cyclohexadienone ring serves to regioselectively direct these cyclizations based primarily on electronic effects. In the case of brominated substrates, these reactions proceed to give highly unusual electron-deficient tricyclic cyclopropanes. By using a Cinchona alkaloid-based phase-transfer catalyst