Co(III)-Catalyzed Enaminone-Directed C–H Amidation for Quinolone Synthesis

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

[Cp*RhIII ]/Ionic Liquid as a Highly Efficient and Recyclable Catalytic Medium for C-H Amidation

A [Cp*Rh^III ]-catalyzed direct C-H amidation is carried out in ionic liquid. Both C(sp² )-H bonds of (hetero)arenes and alkenes and unactivated C(sp³ )-H bonds can be easily amidated with high functional-group tolerance and excellent yields under these conditions. Notably, using [Cp*Rh^III ]/[BMIM]BF₄ (BMIM=1-butyl-3-methylimidazolium) as the green and recyclable medium is environmentally benign, in light of characteristics such as the reusability of the expensive rhodium catalyst, avoidance of highly toxic organic solvents, and mild reaction conditions, as well as a short reaction time.

A comprehensive overview of directing groups applied in metal-catalysed C-H functionalisation chemistry

The present review is devoted to summarizing the recent advances (2015-2017) in the field of metal-catalysed group-directed C-H functionalisation. In order to clearly showcase the molecular diversity that can now be accessed by means of directed C-H functionalisation, the whole is organized following the directing groups installed on a substrate. Its aim is to be a comprehensive reference work, where a specific directing group can be easily found, together with the transformations which have been carried out with it. Hence, the primary format of this review is schemes accompanied with a concise explanatory text, in which the directing groups are ordered in sections according to their chemical structure. The schemes feature typical substrates used, the products obtained as well as the required reaction conditions. Importantly, each example is commented on with respect to the most important positive features and drawbacks, on aspects such as selectivity, substrate scope, reaction conditions, directing group removal, and greenness. The targeted readership are both experts in the field of C-H functionalisation chemistry (to provide a comprehensive overview of the progress made in the last years) and, even more so, all organic chemists who want to introduce the C-H functionalisation way of thinking for a design of straightforward, efficient and step-economic synthetic routes towards molecules of interest to them. Accordingly, this review should be of particular interest also for scientists from industrial R&D sector. Hence, the overall goal of this review is to promote the application of C-H functionalisation reactions outside the research groups dedicated to method development and establishing it as a valuable reaction archetype in contemporary R&D, comparable to the role cross-coupling reactions play to date.

Weinreb Amide Directed Versatile C-H Bond Functionalization under (η5 -Pentamethylcyclopentadienyl)cobalt(III) Catalysis

The (η⁵ -pentamethylcyclopentadienyl)cobalt(III) (Cp*Co^III )-catalyzed C-H bond functionalization of aromatic, heteroaromatic, and α,β-unsaturated Weinreb amides was explored. C-H allylation reactions with the use of allyl carbonate and a perfluoroalkene, oxidative alkenylation reactions with the use of ethyl acrylate, iodination reactions with the use of N-iodosuccinimide, and amidation reactions with the use of dioxazolones were catalyzed by Cp*Co(CO)I₂ in the presence of a cationic Ag salt and AgOAc to afford various synthetically useful building blocks. Mechanistic studies of the C-H allylation disclosed that the C-H activation step was rate determining and virtually irreversible.

Synthesis of 2,5-disubstituted oxazoles via cobalt(iii)-catalyzed cross-coupling of N-pivaloyloxyamides and alkynes

An efficient synthesis of 2,5-disubstituted oxazoles via cobalt(iii)-catalyzed cross-coupling of N-pivaloyloxyamides and alkynes is described herein.

A copper-catalyzed three component reaction of aryl acetylene, sulfonyl azide and enaminone to form iminolactone via 6π electrocyclization

We developed a copper-catalyzed three component reaction of aryl acetylene, enaminone and sulfonyl azide to construct iminolactone via copper-catalyzed alkyne–azide cycloaddition (CuAAC), Michael addition of metalated ketenimine followed by elimination and 6π electrocyclization.

Cp*Rh(iii)-catalyzed annulation of N-methoxybenzamide with 1,4,2-bisoxazol-5-one toward 2-aryl quinazolin-4(3H)-one derivatives

A [Cp*Rh^III]-catalyzed annulation of N-methoxybenzamide with 1,4,2-bisoxazol-5-one was developed, affording a series of 2-aryl quinazolin-4(3H)-one derivatives.

Synthesis of 2-aminobenzaldehydes by rhodium(iii)-catalyzed C–H amidation of aldehydes with dioxazolones

Various aldehydes were directly amidated with dioxazolones to afford 2-aminobenzaldehydes through rhodium(iii)-catalyzed CHO-directed C–H activation.

Cobalt-catalyzed C–H activation: recent progress in heterocyclic chemistry

Cobalt-catalyzed C–H activation has gone through some major advancements in the past couple of decades.

Recent advances using [Cp*Co(CO)I2] catalysts as a powerful tool for C–H functionalisation

This perspective highlights recent applications of Cp*Co^III catalysts in C–H functionalisation protocols, exemplifying both terminal couplings and heterocycle formation.