A 2:1 coupling reaction of arynes with aldehydes via o-quinone methides: Straightforward synthesis of 9-arylxanthenes
(Chemical Equation Presented) A novel coupling reaction, where an aldehyde and two molar amounts of an aryne are assembled selectively, has been demonstrated to afford diverse 9-arylxanthene derivatives in one step. o-Quinone methide arising from the [2 + 2] cycloaddition of an aldehyde with an aryne was postulated as a transient intermediate.
Palladium-copper catalyzed C(sp3)-C(sp2) bond C-H activation cross-coupling reaction: Selective arylation to synthesize 9-aryl-9: H -xanthene and 9,9-diaryl-xanthene derivatives
A novel cooperatively catalyzed C(sp3)-C(sp2) bond C-H activation cross-coupling reaction has been developed. A series of 9-aryl-9H-xanthenes and 9,9-diaryl-xanthenes were selectively synthesized in moderate to good yields by control
Synergistic effect of ketone and hydroperoxide in Bronsted acid catalyzed oxidative coupling reactions
Waste not wasted: A mechanistic study of the autoxidative coupling of xanthene with cyclopentanone uncovered an autoinductive effect of the waste product hydrogen peroxide. It generates radicals in the presence of acid and ketones, which accelerate the reaction by providing an additional pathway to the reactive hydroperoxide intermediate. This discovery could be applied to achieve other Bronsted acid catalyzed oxidative coupling reactions.
Schweitzer-Chaput, Bertrand,Sud, Abhishek,Pinter, Aron,Dehn, Stefanie,Schulze, Philipp,Klussmann, Martin
supporting information
p. 13228 - 13232
(2014/01/06)
Sulfonic acid-catalyzed autoxidative carbon-carbon coupling reaction under elevated partial pressure of oxygen
An aerobic organocatalytic oxidative C-C bond formation reaction of benzylic C-H bonds with various C-nucleophiles is described. The coupling reaction proceeds by simply stirring the substrates under elevated partial pressure of oxygen in the presence of a sulfonic acid catalyst at room temperature. Elevation of the pressure enables the reaction of a broad scope of nucleophile substrates otherwise showing poor reactivity at ambient pressure. The benzylic C-H bonds of xanthene, acridanes, isochromane and related heterocycles could be functionalized with nucleophiles including ketones, 1,3-dicarbonyl compounds and aldehydes. Electron-rich arenes could be utilized as nucleophiles at elevated temperatures. The reactions are believed to proceed via autoxidation of the benzylic C-H bonds to the hydroperoxides and subsequent nucleophilic substitution catalyzed by sulfonic acids. Copyright
Pinter, Aron,Klussmann, Martin
supporting information; experimental part
p. 701 - 711
(2012/04/23)
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