Manganese- and Borane-Mediated Synthesis of Isobenzofuranones from Aromatic Esters and Oxiranes via C–H Bond Activation

Abstract

A manganese- and borane-mediated synthesis of isobenzofuranones from esters and oxiranes is developed. The reaction proceeded at aromatic, heteroaromatic, and olefinic C-H bonds with high functional group tolerance. This is the first example of a manganese-catalyzed C-H transformation using an oxygen-directing group. Triphenylborane played an important role in this reaction to cooperatively promote the annulation reaction. Kinetic isotope effect experiments revealed that C-H bond activation of the aromatic rings was the rate-determining step.

Methylenecyclopropane Annulation by Manganese(I)‐Catalyzed Stereoselective C−H/C−C Activation

“…Based on our mechanistic studies and literature precedence, [5][6][7][8][9] we propose aplausible catalytic cycle to be initiated by aa cetate-assisted organometallic C À Ha ctivation through chelation assistance (Scheme 6). Thereafter,C À Ccleavage [18] occurs to deliver the intermediate 8,w hich subsequently undergoes intramolecular nucleophilic attack.…”

“…Theu nique performance of the manganese(I) catalysis was reflected by attempted C À H/C À Ca ctivations with either manganese(II) salts or frequently used cobalt, ruthenium, rhodium, and palladium catalysts,all of which fell short in delivering any of the desired product 3aa (entries [6][7][8][9][10][11][12]. Theu nique performance of the manganese(I) catalysis was reflected by attempted C À H/C À Ca ctivations with either manganese(II) salts or frequently used cobalt, ruthenium, rhodium, and palladium catalysts,all of which fell short in delivering any of the desired product 3aa (entries [6][7][8][9][10][11][12].…”

“…[3] While notable progress has been realized with precious 4d and 5d transition-metal catalysts,recent focus has shifted towards the use of naturally abundant base metals. [4] In this context, considerable recent advances have been realized with less toxic organometallic manganese(I) catalysis, [5] with key contributions by the groups of Kuninobu, [6] Wang, [7] and Ackermann, [8] among others. [9] As ignificant stimulus in CÀHa ctivation chemistry has very recently been gained by merging CÀHfunctionalization with challenging C À C [10,11] cleavage strategies.I ns pite of these undisputed advances,catalytic [12] C À H/C À Cfunctionalizations continue to be scarce,w ith the reported examples thus far calling for precious rhodium catalyst, [13] and/or activated vinylcyclopropanes.…”

Synergistic Manganese(I) C−H Activation Catalysis in Continuous Flow: Chemoselective Hydroarylation

“…[4] While notable progress was accomplished with noble 4d and 5d transition metals,r ecent focus has shifted towards the use of more sustainable 3d base metals. [5] In this context, considerable recent advances were achieved with the aid of less toxic manganese catalysis, [6] with key contributions by the groups of Kuninobu/Takai, [7] Wang, [8] and Ackermann, [9] among others. [10] Am ajor stimulus has very recently been gained by substitutive CÀHf unctionalizations through hydroarylations with concurrent b-O-elimination processes.W hile this represented significant progress,i ta tt he same time constituted amajor limitation in hydroarylation [11] catalysis.Hence, all manganese-catalyzed hydroarylations of substrates,b earing leaving groups in proximity to the C À Cm ultiple bond, thus far resulted in b-heteroatom eliminations.…”

Hochselektive Mangan(I)/Lewis‐Säure‐cokatalysierte direkte C‐H‐Propargylierung unter Verwendung von Bromallenen

“…[13] In diesem Bereich wurden in den letzten Jahren bedeutende Fortschritte von den Gruppen von Kuninobu und Takai, [14] Wang [15] und Ackermann [16] sowie unserer Gruppe [17] und anderen erzielt. Mangankomplexe werden hingegen immer noch selten verwendet, obwohl Mangan reichlich vorhanden, günstig und wenig toxisch ist.…”