Cobalt-catalyzed coupling reactions of 2-halobenzamides with alkynes: investigation of ligand-controlled dual pathways

Abstract

The Co-catalyzed reactions of 2-halobenzamides and alkynes to form isoquinolones or 2-vinyl benzamides are described. Formation of the two selective products can be fully controlled by adopted ligands. Study of...

Cobalt-Catalyzed Cyclization of 2-Bromobenzamides with Carbodiimides: A New Route for the Synthesis of 3-(Imino)isoindolin-1-ones

“…Based on the above results and a previous report [ 35 ], we propose the reaction mechanism of this cobalt-catalyzed cyclization reaction as below ( Scheme 5 ). The reaction is likely to be initiated by reduction of the Co(II) catalyst to form an active Co(I) species, which activates the C-Br bond of substrate 1 via oxidative addition or a two-times single-electron-transfer process to form the resulting Co(III) complex A [ 20 ].…”

“…We carried out the cobalt-catalyzed cyclization reaction of 2-bromobenzamides with alkynes [ 35 ], then attempted to replace alkynes with carbodiimides to investigate the reactivity of this replacement. Our study started from the optimization of the reaction conditions by using the model substrates 2-bromo- N -methylbenzamide ( 1a ) and N , N ’-dicyclohexylcarbodiimide ( 2a ) with various cobalt catalysts and bases.…”

“…The results are summarized in Table 1 . We first surveyed the optimized condition of our previous reaction [ 35 ]; however, the desired product 3a was obtained in only 47% yield (Entry 1). Although the reaction proceeded smoothly, this result was still unsatisfying and thus made us further investigate various factors of the conditions for this cobalt catalytic cyclization reaction.…”

“…A variety of late-transition-metals have been shown to possess the ability to form this intermediate for further transformations [ 5 , 7 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], which have been commonly indicated to construct six- or five-membered N -heterocyclic structures via the 1,2- or 1,1-insertion of molecules containing multiple bonds. For those revealed catalysts, the first-row transition-metal complexes exhibit comparably higher economic efficiency, and our continuing studies on cobalt-catalyzed coupling reactions [ 25 ], as well as the experiences in cyclization reactions [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], encouraged us to attempt the synthesis of diverse N -heterocyclic scaffolds by using the five-membered cobalacycle intermediate and switching different cyclization partners ( Scheme 2 ). Under this reaction concept, we were able to obtain several N -heterocyclic compounds, including indenoisoquinolinones, chiral 1-aminoindenes, and isoquinolones.…”

A Ruthenium-Catalyzed Cyclization to Dihydrobenzo[c]phenanthridinone from 7-Azabenzonorbornadienes with Aryl Amides

“…The benzo­[ c ]­phenanthridine alkaloid represents an important class of biologically active molecules and has found widespread application in the pharmaceutical industry . Generally, based on structures, these alkaloids are classified into three categories, namely, aromatic benzophenathridines, 13,14-dehydrobenzophenanthridines, and hexahydrobenzophenanthridines.…”