A General and Highly Selective Cobalt‐Catalyzed Hydrogenation of N‐Heteroarenes under Mild Reaction Conditions

Abstract

Herein, a general and efficient method for the homogeneous cobalt-catalyzed hydrogenation of N-heterocycles, under mild reaction conditions, is reported. Key to success is the use of the tetradentate ligand tris(2-(diphenylphosphino)phenyl)phosphine). This non-noble metal catalyst system allows the selective hydrogenation of heteroarenes in the presence of a broad range of other sensitive reducible groups.

Directly Bridging Indoles to 3,3′‐Bisindolylmethanes by Using Carboxylic Acids and Hydrosilanes under Mild Conditions

“…In addition, the common metal-based Lewis acids failed in promoting this reaction (entries 5-7). The unique catalytic activity of B(C 6 F 5 ) 3 may be attributed to its ability to form af rustrated Lewis pair with acarboxyl group to activate the hydrosilane, [11c] which derives from both the Lewis acid center, that is, electrophilic borane, and large steric hindrance of B(C 6 F 5 ) 3 .S ubsequently, varioush ydrosilanes were investigated for the reductive alkylation of 1a with formic acid (entries 4a nd [8][9][10][11][12]. PMHS (polymethylhydrosiloxane), Ph 3 SiH, and PhSiH 3 were found to be inactive (entries8-10).…”

“…Therefore, we speculated that carboxylic acid could also act as alkylating agent to run reductive C−C bond couplings. To the best of our knowledge, direct synthesis of BIM from indole with carboxylic acid has not been explored and only a related example for the cobalt‐catalyzed alkylation of indole with carboxylic acid was described in which BIM was only identified as a byproduct (yield <5 %) . Notably, as a typical carboxylic acid, formic acid can be prepared from CO 2 through catalytic hydrogenation .…”

“…To the best of our knowledge,d irect synthesis of BIM from indole with carboxylic acid has not been explored and only ar elated example for the cobalt-catalyzed alkylation of indole with carboxylic acid was described in which BIM was only identified as ab yproduct (yield < 5%). [12] Notably,a satypical carboxylic acid, formic acid can be prepared from CO 2 through catalytic hydrogenation. [13] From this perspective, reductive alkylation by using formic acid as aC 1s ynthon can be considered as indirect utilization of CO 2 ,t hus providing an alternative synthetic methoda nd promising protocolf or CO 2 utilization.…”

Environmental Catalysis: Present and Future

“…Another promising strategy for the development of a more sustainable chemistry and particularly catalysis, representing as well an economic advantage, is the replacement of noble metal catalyst by non‐noble metal catalytic systems (Figure ) . Although there is still a long way to go in order to achieve such objective, some studies have reported the use of transition metal nanoparticles as hydrogenation catalysts with encouraging performance . For instance, Abe and coworkers have explore the replacement of Pt‐based catalysts by a supported Cu−Ni nanomaterial with potential applicability for gas phase reactions ,…”

Gold(I)‐Catalysed Hydroarylation of Lactam‐Derived Enynes as an Entry to Tetrahydrobenzo[g]quinolines

“…Hence, many bioactive compounds based on this scaffold are used as drugs and agrochemicals, and some efforts have been devoted to their synthesis . In particular, tetrahydrobenzoquinolines have been synthesized by cycloaromatization, ring expansion, hydrogenation, and more recently by Au(I)‐catalysed formal [4+2] cycloaddition . In continuation of our studies on the chemistry and synthetic applications of lactam‐derived enol phosphates and triflates, we recently reported that N ‐protected‐2‐alkynyl tetrahydropyridines are versatile substrates for gold‐catalysed transformations.…”