Cobalt(III)‐Catalyzed CH/NO Functionalizations: Isohypsic Access to Isoquinolines

Wang, Hui; Koeller, Julian; Liu, Weiping; Ackermann, Lutz

doi:10.1002/chem.201503624

Cited by 185 publications

(45 citation statements)

References 89 publications

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“…In both cases, AgSbF 6 was necessary to achieve satisfied yields. For Ackermann's reaction system (Scheme ), the site‐selectivity took place at the sterically less hindered position, while the existence of a secondary interaction (F, dioxole) furnished the product at the congested position . In many substrates, high yielding C−H/N−O functionalization was observed within only 15 min.…”

Section: C−h Activation/functionalizations Catalyzed By Using Cp*coimentioning

confidence: 95%

High‐Valent‐Cobalt‐Catalyzed C−H Functionalization Based on Concerted Metalation–Deprotonation and Single‐Electron‐Transfer Mechanisms

et al. 2016

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C−H functionalization has been established as a powerful strategy for the commercial construction of organic molecules. This review encompasses the most recent advances in C−H activation catalyzed by earth‐abundant cobalt complexes, involving two types of fundamental reaction paths, that is, the concerted metalation–deprotonation (CMD) path associated with non‐oxidative C−H activation and the intermolecular single‐electron‐transfer (SET) path. Transformations catalyzed by high‐valent cobalt based on the two mechanisms and used in organic syntheses, including those involving C−C and C−X (X=O and N) bond formation, are herein presented.

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Section: C−h Activation/functionalizations Catalyzed By Using Cp*coimentioning

confidence: 95%

High‐Valent‐Cobalt‐Catalyzed C−H Functionalization Based on Concerted Metalation–Deprotonation and Single‐Electron‐Transfer Mechanisms

et al. 2016

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“…[1] Tr ansition metals mediate the efficient and selective activation of CÀHb onds,w ith recent attention focusing on environmentally benign and sustainable metals,f or example, Mn, Co,F e, and Cu. [2] Mn I promotes CÀHa ctivation of substrates containing nitrogen-directing groups. [3] Fore xample, 1 gives cyclomanganated complex 2,w ith subsequent reaction with alkyne 3 forming aproposed 7-membered ring intermediate 4 (Scheme 1).…”

mentioning

confidence: 99%

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

et al. 2016

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Manganese-catalyzed C À Hbond activation chemistry is emerging as ap owerful and complementary method for molecular functionalization. Ah ighly reactive seven-membered Mn I intermediate is detected and characterized that is effective for H-transfer or reductive elimination to deliver alkenylated or pyridinium products,r espectively.T he two pathwaysa re determined at Mn I by judicious choice of an electron-deficient 2-pyrone substrate containing a2 -pyridyl directing group,w hichu ndergoes regioselective C À Hb ond activation, serving as av aluable system for probing the mechanistic features of Mn CÀHb ond activation chemistry.C À Hb ond activation-functionalization chemistry is ac entral arena for catalyst development and synthetic application.[1] Tr ansition metals mediate the efficient and selective activation of CÀHb onds,w ith recent attention focusing on environmentally benign and sustainable metals,f or example, Mn, Co,F e, and Cu.[2] Mn I promotes CÀHa ctivation of substrates containing nitrogen-directing groups.[3] Fore xample, 1 gives cyclomanganated complex 2,w ith subsequent reaction with alkyne 3 forming aproposed 7-membered ring intermediate 4 (Scheme 1).[4] Formation of either 5, 6,o r7 results from reductive elimination, H-transfer,o rd ehydrogenative annulation, respectively.Processes utilizing Mn I ,p articularly [Mn(C^N)(CO) 4 ] 2, [5, 6] have been of broad interest. Them echanistic features of the remarkable synthetic work of Ackermann and Wang, [3,4] where intermediates 4a-c have been proposed, prompted us to examine whether they could be detected and characterized and then subsequently be shown to deliver organic products such as 5-7.C omplexes 4d-f,f ormed by insertion of internal alkynes are known, [6,7] but their competence in terms of af ully connected reaction system, affording organic products,h as not been examined. As 18-electron species containing four CO ligands,p ossessing high thermodynamic stability,t hey are unlikely to be directly involved in the catalytic cycle.[8]Herein we describe asuitable reaction system (1g!4g! 5g or 6g,S cheme 1) that takes advantage of the exquisite reactivity of an electron-deficient 2-pyrone ring system containing a2 -pyridyl directing group (1g). We recognized that the 2-pyrone could act as ah emilabile ligand in 7-membered manganacycle 4g,p otentially providing sufficient stabilisation for observation of this key intermediate.O ur findings demonstrate that 4g acts as ac entral manifold to reductive elimination and H-transfer, giving products 5g and 6g,respectively,w ith details described herein.Our study began with the reaction of 2-pyrone 1g with BnMn(CO) 5 in hexane at 75 8 8C, which gave cyclometalated 2g cleanly and in quantitative yield (Scheme 2). Complex 2g was fully characterized (see the Supporting Information);asingle crystal X-ray structure confirmed that regioselective CÀH activation occurred at C3, in keeping with Pd II -direct arylations of 2-pyrones, [9] albeit most likely by a s-CAM-type process. [10] We hypothesized tha...

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“…The transition‐metal catalyzed synthesis of isoquinolines via redox‐neutral strategy is well documented in the literature and in that context, many noble metals have been used . Nonetheless, Co III ‐catalyzed redox‐neutral directed synthesis of isoquinolines was not reported and very recently, this was independently achieved by Kanai/Matsunaga, Ackermann, Sundararaju, and Cheng from the coupling of various oximes with alkynes. A variety of functional groups on oximes and different type of alkynes, including aliphatic alkynes, terminal alkynes were well tolerated, and excellent regioselectivity was observed with internal alkynes under these reaction conditions.…”

Section: Cocp* Catalyzed Annulation Reactionsmentioning

confidence: 99%

Cobalt‐Catalyzed Annulation Reactions via C−H Bond Activation

2018

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Considerable research attention has been directed towards the use of first‐row transition metals in organic synthesis. The more abundant, and less expensive cobalt is considered to be an effective alternative for expensive second and third‐row noble metals, especially in C−H bond functionalization reactions. In this Minireview, we will summarize the features, and recent achievements of the Co‐catalyzed directing group assisted C−H activation/cyclization reactions and their mechanistic insights.

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Cobalt(III)‐Catalyzed CH/NO Functionalizations: Isohypsic Access to Isoquinolines

Abstract: C-H/N-O functionalizations by cobalt(III) catalysis allowed the expedient synthesis of a broad range of isoquinolines. Thus, internal and challenging terminal alkynes proved to be viable substrates for an isohypsic annulation, which was shown to proceed by a facile C-H cobaltation.

Cited by 185 publications

References 89 publications

High‐Valent‐Cobalt‐Catalyzed C−H Functionalization Based on Concerted Metalation–Deprotonation and Single‐Electron‐Transfer Mechanisms

High‐Valent‐Cobalt‐Catalyzed C−H Functionalization Based on Concerted Metalation–Deprotonation and Single‐Electron‐Transfer Mechanisms

Manganese(I)‐Catalyzed C−H Activation: The Key Role of a 7‐Membered Manganacycle in H‐Transfer and Reductive Elimination

Cobalt‐Catalyzed Annulation Reactions via C−H Bond Activation

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