Carbonyl-assisted reverse regioselective cascade annulation of 2-acetylenic ketones triggered by Ru-catalyzed C–H activation

Gollapelli, Krishna Kumar; Kallepu, Shivakrishna; Nagendra, G.; Nanubolu, Jagadeesh Babu; Chegondi, Rambabu

doi:10.1039/c6sc01456a

Cited by 76 publications

(29 citation statements)

References 72 publications

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“…To reverse the intrinsic regioselectivity, tether‐mediated intramolecular cyclizations have been introduced . Alternatively, 2‐acetylenic ketones with weakly coordinated carbonyl groups could be applied . As internal alkyne equivalents, diazo compounds led to annulated heterocycles with specific regioselectivities .…”

Section: Methodsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Heterocycles by Rhodium(III)‐Catalyzed Annulation of N‐Methoxyamides with α‐Chloroaldehydes

Huang

Bolm

2017

Angew Chem Int Ed

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α‐Chloroaldehydes have been used as alkyne equivalents in rhodium‐catalyzed syntheses of isoquinolones and 3,4‐dihydroisoquinolins starting from N‐methoxyamides. Compared to the existing technology, a complementary regioselectivity is achieved. Mechanistic investigations have been performed, and it was found that steric effects of both substrate and additive determine the product selectivity. Various other heterocycles, such as isoquinolines and lactones, can be prepared by transformation of the obtained products.

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Section: Methodsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Heterocycles by Rhodium(III)‐Catalyzed Annulation of N‐Methoxyamides with α‐Chloroaldehydes

Huang

Bolm

2017

Angew Chem Int Ed

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“…Electron‐donating Cp ligands will more readily induce [4+2] alkyne insertion into the rhodacycle to give the seven‐membered rhodacycle III‐2 , which then undergoes reductive elimination with N−O bond cleavage to furnish isoquinolinone IV‐2 . Finally, base‐mediated cyclization of IV‐2 provides tbe [4+2] product …”

Section: Methodsmentioning

confidence: 99%

[4+2] or [4+1] Annulation: Changing the Reaction Pathway of a Rhodium‐Catalyzed Process by Tuning the Cp Ligand

2017

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A change in reaction pathway was achieved for the first time by tuning the cyclopentadienyl (Cp) ligand used for the rhodium‐catalyzed cyclization of benzamides with conjugated enynones. Depending on the Cp ligand, the reaction pathway switched between [4+2] and [4+1] annulation. Electronic effects turned out to be crucial for the product distribution. The dichotomy was attributed to the alteration of the Lewis acidity of the resultant Cp‐bound rhodium species.

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“…[81] The intermolecular weak coordination of the carbonyl group to Ru(II) center sets up the regioselectivity for the alkyne insertion. Subsequent reductive elimination and re-oxidation of the catalyst followed by an intramolecular nucleophilic attack from the amide to the carbonyl group delivers the product.…”

Section: Ruthenium Catalysismentioning

confidence: 99%

A Simple and Versatile Amide Directing Group for C−H Functionalizations

et al. 2016

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Achieving selective C–H activation at a single and strategic site in the presence of multiple C–H bonds can provide a powerful and generally useful retrosynthetic disconnection. In this context, the directing group serves as a compass to guide the transition metal to C–H bonds using distance and geometry as powerful recognition parameters to distinguish between proximal and distal C–H bonds. However, the installation and removal of directing groups is a practical drawback. To improve the utility of this approach, one can seek solutions in three directions. First, simplifying the directing group; Second, use of common functional groups or protecting groups as directing groups; Third, attaching the directing group to substrates via a transient covalent bond to render directing groups catalytic. This review describes the rational development of an extremely simple and yet broadly applicable directing group for Pd(II), Rh(III) and Ru(II) catalysts, namely, the N-methoxy amide (CONHOMe). Through collective efforts in the community, a wide range of C–H activation transformations using this type of simple directing groups has been developed.

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Carbonyl-assisted reverse regioselective cascade annulation of 2-acetylenic ketones triggered by Ru-catalyzed C–H activation

Abstract: The first reverse regioselective intermolecular annulation of aryl substituted 2-acetylenic ketones with O-substituted N-hydroxybenzamides or acrylamides followed by tandem cyclization via ruthenium-catalyzed C–H activation, is reported.

Cited by 76 publications

References 72 publications

Microwave‐Assisted Synthesis of Heterocycles by Rhodium(III)‐Catalyzed Annulation of N‐Methoxyamides with α‐Chloroaldehydes

Microwave‐Assisted Synthesis of Heterocycles by Rhodium(III)‐Catalyzed Annulation of N‐Methoxyamides with α‐Chloroaldehydes

[4+2] or [4+1] Annulation: Changing the Reaction Pathway of a Rhodium‐Catalyzed Process by Tuning the Cp Ligand

A Simple and Versatile Amide Directing Group for C−H Functionalizations

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