C-H bond activation Research Papers (original) (raw)

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.

- by Carlo Sambiagio and +1
- •
- Organic Chemistry, Catalysis, Synthetic Organic Chemistry, Organic Synthesis

Traditional cross-coupling reactions, like Mizoroki-Heck Reaction and Suzuki Reaction, have revolutionized organic chemistry and are widely applied in modern organic synthesis. With the rapid development of C–H activation and asymmetric catalysis in recent years, enantioselective C–H activation/cross-coupling reactions have drawn much attention from researchers. This review summarizes recent advances in enantioselective C–H activation/Mizoroki-Heck Reaction and Suzuki Reaction, with emphasis on the structures and functions of chiral ligands utilized in different reactions.

- by Shah Nawaz Khan and +2
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- C-H bond activation, Enantioselectivity, Suzuki and Heck Coupling Reactions
- by Oana Luca
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- Quinones, C-H bond activation, Oxidation, DDQ Oxidant

Pyrans constitute an important class of 6-member heterocycles with one oxygen atom. Together with its benzo derivatives, pyrans can formulate a prevalent verity of natural and synthetic products with industrial applications. This is an important core molecule having versatile use with its derivatives in pharmaceuticals, dye industry, catalysis, agrochemicals and many more. Several methods for the preparation of pyran derivatives have been reported earlier. This article reports the development of an efficient method for the construction of a fused pyran ring by intramolecular Heck reaction followed by β-H elimination from O-allylated ether. A tetracyclic pyran ring has also been synthesized by intramolecular Heck reaction followed by C–H bond activation from O-methallylated ether.

- by Gourisankar Roymahapatra
- •
- C-H bond activation, heck reaction

The complex [Ru(bpy)2(ttma)]+ (bpy = 2,2’-
bipyridine; ttma = 3-hydroxy-2-methylthiopyran-
4-thionate, 1, has previously been
shown to undergo an unusual C-H activation of
the dithiomaltolato ligand upon outer-sphere
oxidation. The reaction generated alcohol and
aldehyde products 2 and 3 from C-H oxidation
of the pendant methyl group. In this report, we
demonstrate that the same products are formed
upon photolysis of 1 in presence of mild
oxidants such as methyl viologen,
[Ru(NH3)6]3+ and [Co(NH3)5Cl]2+, which do
not oxidize 1 in the dark.
This reactivity is engendered only upon
excitation into an absorption band attributed
to the ttma ligand. Analogous experiments
with the homoleptic Zn(ttma)2, 4, also result
in reduction of electron acceptors upon
excitation of the ttma absorbance band.
Complexes 1 and 4 exhibit short-lived
visible fluorescence and long-lived nearinfrared
phosphorescence bands. Singlet
oxygen is both generated and quenched
during aerobic excitation of 1 or 4, but is not
involved in the C-H activation process.

- by farooq zia
- •
- Organic Chemistry, Catalysis, Synthetic Organic Chemistry, Organic Synthesis

A simple and highly practical method for the synthesis of 2-N-substituted benzothiazoles has been
developed by using nano copper ferrite as a magnetically separable, recyclable catalyst. The present
tandem process allows to get access to a wide range of 2-N-substituted benzothiazoles in good to
excellent yields by the reaction of benzothiazole with nitrogen nucleophiles in the presence of Cs2CO3 as a base. The nano CuFe2O4 could be recovered and reused with no significant loss of catalytic activity.

- by Dr. Harsha Vardhan Reddy Kasireddy
- •
- C-H bond activation

Ap aper-based colorimetrics ensor system (PBCSS)w as developedt od etect the amounto fb is(pina-colato)diboron(B 2 Pin 2)a nd applied as ah igh-throughput screening protocol in Ir-catalyzed CÀHb orylation. First, 96 ligandsw ere screened for the borylation of benzene,a nd then 12 of them were selected and tested for five sub-strates.T hese reactionm ixtures were spotted in the PBCSS,s howingablue-violet color.T he value of the gray scale of each reaction was obtained from these colored spots and converted to the extent of conversion of B 2 Pin 2. The extentso fc onversion of B 2 Pin 2 obtained from the PBCSS showed good correlation with those obtained from gas chromatography analysis.I na ddition, the modified conversion using blank data showedg ood correlation with the yield of products.

- by Sunwoo Lee
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- High throughput screening, C-H bond activation, Borylation

Rhodium catalysed dehydrogenative C-H/N-H functionalization was developed to construct phthalazino[2,3-a]-/indazolo[1,2-a]cinnolines by reacting N-phenyl phthalazine/indazole with alkynes. The synthesized compounds exhibit prominent fluorescence properties in solid and aggregation states. Their application in cell imaging was investigated using various cancer cell lines.

- by Paramasivan Perumal
- •
- Organic Chemistry, Medicinal Chemistry, Catalysis, Fluorescence

We describe here an efficient ruthenium-catalyzed C–H bond ortho-arylation of 9-(pyrimidin-2-yl)-9H-carbazole by using boronic acids. This methodology exhibits excellent and high site-selectivity, functional group tolerance and was found... more

Tetrabutylammonium decatungstate (TBADT) has emerged as an efficient and versatile photocatalyst for hydrogen atom transfer (HAT) processes that enables the cleavage of both activated and unactivated aliphatic C−H bonds. Using a recently developed oscillatory millistructured continuous-flow photoreactor, investigations of a decatungstate-catalyzed C(sp 3)−H alkylation protocol were carried out, and the results are presented here. The performance of the reactor was evaluated in correlation to several chemical and process parameters, including residence time, light intensity, catalyst loading, and substrate/reagent concentration. In comparison with previously reported batch and flow protocols, conditions were found that led to considerably higher productivity, achieving a throughput up to 36.7 mmol/h with a residence time of only 7.5 min.

- by Carlo Sambiagio
- •
- Organic Chemistry, Photochemistry, Flow Chemistry, Organic Synthesis

A copper-catalyzed aerobic oxidation of benzylpyridine N-oxides is reported. The N-oxide moiety acts as a built-in activator for the benzylic methylene oxidation, without requirement of additives. Reaction conditions were identified which suppress undesired benzoylpyridine formation via N-deoxygenation involving intermolecular oxygen transfer. The versatility of the N-oxide group of the benzoylpyridine N-oxide reaction products for post-functionalization of the pyridine ring is demonstrated through efficient C–C, C–N, C–O and C–Cl bond forming procedures, with both nucleophiles and electrophiles. Finally, the applicability of the new synthetic methodology is demonstrated in an alternative route towards the antihistaminic drug Acrivastine via three consecutive N-oxide activated C–H functionalization processes, starting from picoline N-oxide.

The catalytic potential of different metal Lewis acids has been assessed for the one-pot tandem
Friedländer annulation and Knoevenagel condensation involving 2-aminobenzophenone, ethyl
10 acetoacetate, and benzaldehyde to form 2-styryl quinoline under solvent free condition. While various
metal Lewis acids were effective in promoting the Friedländer annulation step, In(OTf)3
was the only
effective catalyst for the subsequent Knoevenagel condensation reaction suggesting In(OTf)3
as the standalone
catalyst for the tandem Friedländer-Knoevenagel reaction to form 2-styryl quinolines. The protocol
is compatible with different variation of aromatic/hetero-aromatic aldehydes and α, β unsaturated
15 aromatic aldehyde giving highly functionalized 2-aryl/heteroaryl vinyl quinolines. The catalyst can be
recovered and reused to afford the desired product in very good to excellent yields.

- by ASIM KUMAR, Ph.D.
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- Medicinal Chemistry, Organocatalysis, Organic Synthesis, C-H bond activation
- by Grigory Shamov
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- Computational Chemistry, Reaction Mechanisms, C-H bond activation

Unusual light induced C–H oxidation initiated by excitation into Ru-bound dithiomaltol ligand absorption.

- by Patrick Farmer
- •
- Chemistry, Inorganic Chemistry, Coordination Chemistry, Electrochemistry
- by Michael Schnürch
- •
- Organic Chemistry, Palladium, C-H bond activation, Benzofuran
- by mayakrishnan S and +2
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- Medicinal Chemistry, Live-cell imaging, Synthetic Organic Chemistry, C-H bond activation