Iron-Catalyzed Cross-Dehydrogenative-Coupling Reactions

Itazaki, Masumi; Nakazawa, Hiroshi

doi:10.1007/3418_2015_105

Cited by 24 publications

(4 citation statements)

References 71 publications

(84 reference statements)

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“…This chemistry is further explained by Masumi Itazaki and Hiroshi Nakazawa in [51]. Two notable examples of the reaction are shown in Scheme 3 [43,44].…”

Section: C-c Bond-forming Reactionsmentioning

confidence: 91%

Iron Catalysis: Historic Overview and Current Trends

Bauer

2015

Topics in Organometallic Chemistry

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Iron catalysis is a growing area of research, as seen by an exponential increase in the publication activities on the topic. This introductory chapter provides a historic overview of the development of iron catalysis including some notable milestones. The advantages of iron, i.e., its abundance, low price, and relative nontoxicity, are discussed, and an overview of the main type of reactions catalyzed by iron is outlined. The advances of heterogeneous iron catalysis (which is not covered in this volume) are exemplified with a few notable cases. Finally, the potential impact of metal impurities in iron sources on the catalytic activity is discussed.

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“…This chemistry is further explained by Masumi Itazaki and Hiroshi Nakazawa in [51]. Two notable examples of the reaction are shown in Scheme 3 [43,44].…”

Section: C-c Bond-forming Reactionsmentioning

confidence: 91%

Iron Catalysis: Historic Overview and Current Trends

Bauer

2015

Topics in Organometallic Chemistry

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“…A growing number of examples, however, suggest that even this assessment needs to be revisited, since iron-catalyzed Fenton-type reactions were tamed and used to form various C−C and C−X bonds by dehydrogenative coupling with appreciable selectivity and yield. 135 ■ THE ROLE OF SPIN STATE AND SPIN CHANGE These and many other examples suggest that the somehow pertinacious view that high-spin iron complexes favor unselective organic transformations is improper at best. Even less appreciated is the possibility that high spin iron complexes may actually provide distinct advantages and could be used as enabling vehicles in catalysis.…”

Section: Reach Of the Noble Cousinsmentioning

confidence: 99%

“…For its aggressiveness, this chemistry was hardly appreciated in a synthetic context. A growing number of examples, however, suggest that even this assessment needs to be revisited, since iron-catalyzed Fenton-type reactions were tamed and used to form various C–C and C–X bonds by dehydrogenative coupling with appreciable selectivity and yield …”

Section: Radical Approaches and Tasks Beyond Reach Of The Noble Cousinsmentioning

confidence: 99%

Iron Catalysis in Organic Synthesis: A Critical Assessment of What It Takes To Make This Base Metal a Multitasking Champion

2016

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The current status of homogeneous iron catalysis in organic chemistry is contemplated, as are the reasons why this particular research area only recently starts challenging the enduring dominance of the late and mostly noble metals over the field. Centered in the middle of the d-block and able to support formal oxidation states ranging from −II to +VI, iron catalysts hold the promise of being able to encompass organic synthesis at large. They are expected to serve reductive as well as oxidative regimes, can emulate “noble tasks”, but are also able to adopt “early” transition metal character. Since a comprehensive coverage of this multidimensional agenda is beyond the scope of an Outlook anyway, emphasis is laid in this article on the analysis of the factors that perhaps allow one to control the multifarious chemical nature of this earth-abundant metal. The challenges are significant, not least at the analytical frontier; their mastery mandates a mindset that differs from the routines that most organic chemists interested in (noble metal) catalysis tend to cultivate. This aspect notwithstanding, it is safe to predict that homogeneous iron catalysis bears the chance to enable a responsible paradigm for chemical synthesis and a sustained catalyst economy, while potentially providing substantial economic advantages. This promise will spur the systematic and in-depth investigations that it takes to upgrade this research area to strategy-level status in organic chemistry and beyond.

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“…One potential solution is to expand the redox sphere beyond the metal center by harnessing cooperative metal–ligand redox processes for multielectron chemistry. ,− In this approach, the capacity of redox-active ligands to store and deliver charge is a tool to bring about precious metal-like two-electron organometallic reactivity at metal ions that are more commonly prone to one-electron transfer or that are even redox inert. This strategy has recently been applied to a wide array of bond-making and -breaking reactions. − However, while redox-active ligand complexes have found some applications in base-metal catalysis, − in most cases advancements are still needed to make these preformed complexes competitive with catalysts generated in situ from base-metal salts, reductants, and potential ligand additives. ,− Successes in rational base-metal catalyst design often begin with robust, tunable ligands. For instance, the redox-active bis(imino)pyridine [NNN] pincer ligands , were termed “privileged” because of their utility in Fe and Co catalysis .…”

Section: Introductionmentioning

confidence: 99%

Redox-Active Bis(phenolate) N-Heterocyclic Carbene [OCO] Pincer Ligands Support Cobalt Electron Transfer Series Spanning Four Oxidation States

et al. 2017

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A new family of low-coordinate Co complexes supported by three redox-noninnocent tridentate [OCO] pincer-type bis(phenolate) N-heterocyclic carbene (NHC) ligands are described. Combined experimental and computational data suggest that the charge-neutral four-coordinate complexes are best formulated as Co(II) centers bound to closed-shell [OCO] dianions, of the general formula [(OCO)CoL] (where L is a solvent-derived MeCN or THF). Cyclic voltammograms of the [(OCO)CoL] complexes reveal three oxidations accessible at potentials below 1.2 V vs Fc/Fc, corresponding to generation of formally Co(V) species, but the true physical/spectroscopic oxidation states are much lower. Chemical oxidations afford the mono- and dications of the imidazoline NHC-derived complex, which were examined by computational and magnetic and spectroscopic methods, including single-crystal X-ray diffraction. The metal and ligand oxidation states of the monocationic complex are ambiguous; data are consistent with formulation as either [(OCO)Co(THF)] containing a closed-shell [OCO] diphenolate ligand bound to a S = 1 Co(III) center, or [(OCO)Co(THF)] with a low-spin Co(II) ion ferromagnetically coupled to monoanionic [OCO] containing a single unpaired electron distributed across the [OCO] framework. The dication is best described as [(OCO)Co(THF)], with a single unpaired electron localized on the d Co(II) center and a doubly oxidized, charge-neutral, closed-shell OCO ligand. The combined data provide for the first time unequivocal and structural evidence for [OCO] ligand redox activity. Notably, varying the degree of unsaturation in the NHC backbone shifts the ligand-based oxidation potentials by up to 400 mV. The possible chemical origins of this unexpected shift, along with the potential utility of the [OCO] pincer ligands for base-metal-mediated organometallic coupling catalysis, are discussed.

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Iron-Catalyzed Cross-Dehydrogenative-Coupling Reactions

Cited by 24 publications

References 71 publications

Iron Catalysis: Historic Overview and Current Trends

Iron Catalysis: Historic Overview and Current Trends

Iron Catalysis in Organic Synthesis: A Critical Assessment of What It Takes To Make This Base Metal a Multitasking Champion

Redox-Active Bis(phenolate) N-Heterocyclic Carbene [OCO] Pincer Ligands Support Cobalt Electron Transfer Series Spanning Four Oxidation States

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