Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light.

Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes.






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Figure 1


Ruthenium polypyridyl complexes: versatile visible light photocatalysts.

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Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

1.1 Introduction to Pd-catalyzed directed C–H functionalization
The development of methods for the direct conversion of carbon–hydrogen bonds into carbon-oxygen, carbon-halogen, carbon-nitrogen, carbon-sulfur, and carbon-carbon bonds remains a critical challenge in organic chemistry. Mild and selective transformations of this type will undoubtedly find widespread application across the chemical field, including in the synthesis of pharmaceuticals, natural products, agrochemicals, polymers, and feedstock commodity chemicals. Traditional approaches for the formation of such functional groups rely on pre-functionalized starting materials for both reactivity and selectivity. However, the requirement for installing a functional group prior to the desired C–O, C–X, C–N, C–S, or C–C bond adds costly chemical steps to the overall construction of a molecule. As such, circumventing this issue will not only improve atom economy but also increase the overall efficiency of multi-step synthetic sequences.

Direct C–H bond functionalization reactions are limited by two fundamental challenges: (i) the inert nature of most carbon-hydrogen bonds and (ii) the requirement to control site selectivity in molecules that contain diverse C–H groups. A multitude of studies have addressed the first challenge by demonstrating that transition metals can react with C–H bonds to produce C–M bonds in a process known as “C–H activation”.1 The resulting C–M bonds are far more reactive than their C–H counterparts, and in many cases they can be converted to new functional groups under mild conditions.

The second major challenge is achieving selective functionalization of a single C–H bond within a complex molecule. While several different strategies have been employed to address this issue, the most common (and the subject of the current review) involves the use of substrates that contain coordinating ligands. These ligands (often termed “directing groups”) bind to the metal center and selectively deliver the catalyst to a proximal C–H bond. Many different transition metals, including Ru, Rh, Pt, and Pd, undergo stoichiometric ligand-directed C–H activation reactions (also known as cyclometalation).2,3 Furthermore, over the past 15 years, a variety of catalytic carbon-carbon bond-forming processes have been developed that involve cyclometalation as a key step.1b–d,4

The current review will focus specifically on ligand-directed C–H functionalization reactions catalyzed by palladium. Palladium complexes are particularly attractive catalysts for such transformations for several reasons. First, ligand-directed C–H functionalization at Pd centers can be used to install many different types of bonds, including carbon-oxygen, carbon-halogen, carbon-nitrogen, carbon-sulfur, and carbon-carbon linkages. Few other catalysts allow such diverse bond constructions,5,6,7 and this versatility is predominantly the result of two key features: (i) the compatibility of many PdII catalysts with oxidants and (ii) the ability to selectively functionalize cyclopalladated intermediates. Second, palladium participates in cyclometalation with a wide variety of directing groups, and, unlike many other transition metals, promotes C–H activation at both sp2 and sp3 C–H sites. Finally, the vast majority of Pd-catalyzed directed C–H functionalization reactions can be performed in the presence of ambient air and moisture, making them exceptionally practical for applications in organic synthesis.

While several accounts have described recent advances, this is the first comprehensive review encompassing the large body of work in this field over the past 5 years (2004–2009). Both synthetic applications and mechanistic aspects of these transformations are discussed where appropriate, and the review is organized on the basis of the type of bond being formed.

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Palladium-Catalyzed Ligand-Directed C−H Functionalization Reactions

https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

Palladium-Catalyzed Synthesis of 2-Substituted Benzothiazoles via a C−H Functionalization/Intramolecular C−S Bond Formation Process

N‐Heterocyclic Carbene Derived Nickel–Pincer Complexes: Efficient and Applicable Catalysts for Suzuki–Miyaura Coupling Reactions of Aryl/Alkenyl Tosylates and Mesylates

Palladium-catalysed direct synthesis of benzo[b]thiophenes from thioenols

A catalytic synthetic approach for the synthesis of 2-quinolinone compounds through a Pd-catalyzed C(sp2)−H functionalization/intramolecular amidation sequence is described. The cyclization process efficiently proceeds in the presence of a catalytic amount of PdCl2 and Cu(OAc)2 under an O2 atmosphere, providing practical access to a range of variously substituted 4-aryl-2-quinolinones.

Takayuki Doi

Papers

Palladium-Catalyzed Synthesis of 2-Substituted Benzothiazoles via a C−H Functionalization/Intramolecular C−S Bond Formation Process

N‐Heterocyclic Carbene Derived Nickel–Pincer Complexes: Efficient and Applicable Catalysts for Suzuki–Miyaura Coupling Reactions of Aryl/Alkenyl Tosylates and Mesylates

Palladium-catalysed direct synthesis of benzo[b]thiophenes from thioenols

Palladium-catalyzed intramolecular amidation of C(sp2)-H bonds: synthesis of 4-aryl-2-quinolinones.

Total synthesis of (R)-telomestatin.