Electrooxidative o-carborane chalcogenations without directing groups: cage activation by copper catalysis at room temperature

Abstract

Copper-catalyzed electrochemical direct chalcogenations of o-carboranes was established at room temperature. Thereby, a series of cage C-sulfenylated and C-selenylated o-carboranes anchored with valuable functional groups was accessed with high levels...

Electrochemical Cage Activation of Carboranes

“…Electrophilic attack of the copper(III) center at the relatively electron-rich B( 4 In contrast to the oxygenation of o-carboranes, Ackermann and co-workers reported an intriguing copper-catalyzed electrochemical cage CÀ H chalcogenations of ocarboranes through a dehydrogenative pathway, notably without a directing group. [34] This approach constitutes an unprecedented strategy for the assembly of a variety of Csulfenylated and C-selenylated o-carborane derivatives 12 under mild conditions (Scheme 11). This electrochemical cage functionalization approach was demonstrated to proceed with good substrate scope and outstanding levels of chemo-and regioselectivity.…”

“…In addition, DFT calculations were also supportive of iodide serving as a competent redox mediator to achieve the transformation from complex V to complex VI (Scheme 13). [34] From the findings of the control experiments and mechanistic studies, a plausible catalytic cycle (Scheme 14) was proposed to feature an anodic single-electron-transfer (SET) oxidation of the thiol anion I to deliver the sulfurcentered radical II, which further reacts with the copper(I) species III to form copper(II) complex IV. Thereafter, carborane cage activation and anodic oxidation by the anodically generated redox mediator I 2 furnishes the copper-(III) species VI, which subsequently undergoes reductive elimination to afford the final product 12 and regenerate the catalytically active complex III.…”

“…In addition, DFT calculations were also supportive of iodide serving as a competent redox mediator to achieve the transformation from complex V to complex VI (Scheme 13). [34] …”

Elektrochemische Carborankäfig‐Aktivierung

“…DFT‐Berechnungen bestätigen die Funktion des Iodids als Redox‐Mediator in der Umwandlungsreaktion von Komplex V zum Komplex VI (Schema 13). [34] …”

“…Im Gegensatz zur Oxygenierung von o ‐Carboranen berichteten Ackermann und Mitarbeiter von einer faszinierenden cupra‐elektrokatalysierten C−H‐Chalkogenierung von o ‐Carborankäfigen auf eine dehydrierende Weise ohne den Einsatz von dirigierenden Gruppen [34] . Letzteres bildet einen beispiellosen Ansatz zum Aufbau einer Vielzahl verschiedener C‐sulfenylierter und C‐selenylierter o ‐Carboranderivate 12 unter milden Reaktionsbedingungen (Schema 11).…”