scholarly journals Electrosynthesis of 3,3′,5,5’-Tetramethyl-2,2′-biphenol in Flow

2020 ◽  
Author(s):  
Maximilian Selt ◽  
Barbara Gleede ◽  
Robert Franke ◽  
Andreas Stenglein ◽  
Siegfried R. Waldvogel
Keyword(s):  
Scale Up ◽  
Transition Metal Catalysis ◽  
Side Reactions ◽  
Narrow Gap ◽  
Metal Catalysis ◽  
Gap Flow ◽  
Electrolysis Cells ◽  
Efficient Alternative ◽  
Synthetic Approaches ◽  
Work Up

Abstract3,3′,5,5’-Tetramethyl-2,2′-biphenol is well known as an outstanding building block for ligands in transition-metal catalysis and is therefore of particular industrial interest. The electro-organic method is a powerful, sustainable, and efficient alternative to conventional synthetic approaches to obtain symmetric and non-symmetric biphenols. Here, we report the successive scale-up of the dehydrogenative anodic homocoupling of 2,4-dimethylphenol (4) from laboratory scale to the technically relevant scale in highly modular narrow gap flow electrolysis cells. The electrosynthesis was optimized in a manner that allows it to be easily adopted to different scales such as laboratory, semitechnical and technical scale. This includes not only the synthesis itself and its optimization but also a work-up strategy of the desired biphenols for larger scale. Furthermore, the challenges such as side reactions, heat development and gas evolution that arose during optimization are also discussed in detail. We have succeeded in obtaining yields of up to 62% of the desired biphenol.

Selective and Scalable Dehydrogenative Electrochemical Synthesis of 3,3′,5,5′-Tetramethyl-2,2′-biphenol

Synlett ◽  
2019 ◽  
Vol 30 (18) ◽  
pp. 2062-2067 ◽  
Author(s):  
Maximilian Selt ◽  
Stamo Mentizi ◽  
Dieter Schollmeyer ◽  
Robert Franke ◽  
Siegfried R. Waldvogel
Keyword(s):  
Transition Metal ◽  
Electrochemical Synthesis ◽  
Building Block ◽  
Electrochemical Method ◽  
Transition Metal Catalysis ◽  
Side Reactions ◽  
Metal Catalysis ◽  
Byproduct Formation ◽  
Chemical Strategies

3,3′,5,5′-Tetramethyl-2,2′-biphenol is a compound of high technical significance, as it exhibits superior properties as building block for ligands in the transition-metal catalysis. However, side reactions and overoxidation are challenging issues in the conventional synthesis of this particular biphenol. Here, an electrochemical method is presented as powerful and sustainable alternative to conventional chemical strategies, which gives good yields up to 51%. Despite using inexpensive and well-available bromide-containing supporting electrolytes, the issue of bromination and general byproduct formation is effectively suppressed by adding water to the electrolyte. Additionally, the scalability of this method was demonstrated by conducting the electrolysis on a 122 g scale.

Homogeneous visible light mediated transition metal catalysis other than Ruthenium and Iridium

2019 ◽  
Vol 4 (7) ◽  
Author(s):  
Lukas Traub ◽  
Oliver Reiser
Keyword(s):  
Transition Metal ◽  
Visible Light ◽  
Metal Complexes ◽  
Coordination Compounds ◽  
Organic Dyes ◽  
Transition Metal Catalysis ◽  
Metal Catalysis ◽  
Iron Nickel ◽  
Efficient Alternative ◽  
Cost Efficient

Abstract The field of photoredox chemistry is dominated by ruthenium- or iridium based metal complexes or organic dyes that are employed as catalysts. Other metal based coordination compounds provide a cost efficient alternative, however, the much shorter excited lifetimes generally observed for such complexes make their application more challenging. Nevertheless, a growing number of successful examples with metal complexes based on chromium, iron, nickel, zirconium, cerium, rhenium, platinum, uranium, and especially on copper exist, which is being reviewed in this chapter.

Total Syntheses of Cylindrocyclophanes Exemplifying the Power of Transition-Metal Catalysis in Natural-Product Synthesis

Synlett ◽  
2020 ◽  
Author(s):  
Bernhard Breit ◽  
Dino Berthold
Keyword(s):  
Transition Metal ◽  
Natural Product ◽  
Biological Properties ◽  
Transition Metal Catalysis ◽  
Natural Product Synthesis ◽  
Metal Catalysis ◽  
Total Syntheses ◽  
Key Steps ◽  
Synthetic Approaches ◽  
Cylindrocyclophane A

Cylindrocyclophanes are a class of naturally occurring 22-membered macrocycles with a unique architecture and interesting physical, chemical, and biological properties. This comprehensive account summarizes progress in various synthetic approaches to these compounds during the last twenty years, thereby emphasizing the key steps for establishing the [7,7]-paracyclophane scaffold, as well as alternative approaches to the construction of its stereocenters. Many of these syntheses highlight the power of transition-metal catalysis for natural-product synthesis. Furthermore, the unraveling of the biosynthesis to these natural products in Cylindrospermum licheniforme is discussed.1 Introduction2 Biosynthesis3 Smith’s Synthesis of (–)-Cylindrocyclophanes A and F4 Hoye’s Synthesis of (–)-Cylindrocyclophane A5 Iwabuchi’s Syntheses of (–)-Cylindrocyclophane A and (+)-Cylindrocyclophane A6 Nicolaou’s Synthesis of (–)-Cylindrocyclophanes A and F7 Breit’s Synthesis of (–)-Cylindrocyclophane F8 Conclusion

scholarly journals Recent Advances on Synthetic Methodology Merging C–H Functionalization and C–C Cleavage

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5900
Author(s):  
Hamid Azizollahi ◽  
José-Antonio García-López
Keyword(s):  
Organic Synthesis ◽  
Recent Progress ◽  
Transition Metal Catalysis ◽  
Synthetic Methodology ◽  
Straightforward Manner ◽  
Metal Catalysis ◽  
Radical Intermediates ◽  
Wide Range ◽  
Radical Initiators ◽  
Synthetic Approaches

The functionalization of C–H bonds has become a major thread of research in organic synthesis that can be assessed from different angles, for instance depending on the type of catalyst employed or the overall transformation that is carried out. This review compiles recent progress in synthetic methodology that merges the functionalization of C–H bonds along with the cleavage of C–C bonds, either in intra- or intermolecular fashion. The manuscript is organized in two main sections according to the type of substrate in which the cleavage of the C–C bond takes place, basically attending to the scission of strained or unstrained C–C bonds. Furthermore, the related research works have been grouped on the basis of the mechanistic aspects of the different transformations that are carried out, i.e.,: (a) classic transition metal catalysis where organometallic intermediates are involved; (b) processes occurring via radical intermediates generated through the use of radical initiators or photochemically; and (c) reactions that are catalyzed or mediated by suitable Lewis or Brønsted acid or bases, where molecular rearrangements take place. Thus, throughout the review a wide range of synthetic approaches show that the combination of C–H and C–C cleavage in single synthetic operations can serve as a platform to achieve complex molecular skeletons in a straightforward manner, among them interesting carbo- and heterocyclic scaffolds.

Carbon‐Sulfur Bond Constructions: From Transition‐Metal Catalysis to Sustainable Catalysis

2021 ◽  
Author(s):  
Pratheepkumar Annamalai ◽  
Ke‐Chien Liu ◽  
Satpal Singh Badsara ◽  
Chin‐Fa Lee
Keyword(s):  
Transition Metal ◽  
Transition Metal Catalysis ◽  
Metal Catalysis ◽  
Sulfur Bond

An electrochemical perspective on the roles of ligands in the merger of transition-metal catalysis and electrochemistry

2020 ◽  
Author(s):  
Ke-Yin Ye ◽  
Jun-Song Zhong ◽  
Yi Yu ◽  
Zhaojiang Shi
Keyword(s):  
Transition Metal ◽  
Organic Synthesis ◽  
Transition Metal Catalysis ◽  
Metal Catalysis

The merger of transition-metal catalysis and electrochemistry has been emerging as a very versatile and robust synthetic tool in organic synthesis. Like in their non-electrochemical variants, ligands also play crucial...

Insertion Reaction of 2-Halo-N-allylanilines with K2S Involving Trisulfur Radical Anion: Synthesis of Benzothiazole Derivatives under Transition-Metal-Free Conditions

Synthesis ◽  
2020 ◽  
Author(s):  
Yan-Wei Zhao ◽  
Shun-Yi Wang ◽  
Xin-Yu Liu ◽  
Tian Jiang ◽  
Weidong Rao
Keyword(s):  
Transition Metal ◽  
Radical Anion ◽  
Radical Cyclization ◽  
Transition Metal Catalysis ◽  
Insertion Reaction ◽  
Metal Catalysis ◽  
Metal Free ◽  
Benzothiazole Derivatives

AbstractA synthesis of benzothiazole derivatives through the reaction of 2-halo-N-allylanilines with K2S in DMF is developed. The trisulfur radical anion S3·–, which is generated in situ from K2S in DMF, initiates the reaction without transition-metal catalysis or other additives. In addition, two C–S bonds are formed and heteroaromatization of benzothiazole is triggered by radical cyclization and H-shift.

scholarly journals Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates

2019 ◽  
Vol 377 (6) ◽  
Author(s):  
Samson Afewerki ◽  
Armando Córdova
Keyword(s):  
Transition Metal ◽  
Metal Complex ◽  
Carbonyl Compounds ◽  
Transition Metal Catalysis ◽  
Chemical Transformations ◽  
Considerable Effort ◽  
Metal Catalysis ◽  
First Report ◽  
Wide Range ◽  
Selective Chemical

AbstractThe concept of merging enamine activation catalysis with transition metal catalysis is an important strategy, which allows for selective chemical transformations not accessible without this combination. The amine catalyst activates the carbonyl compounds through the formation of a reactive nucleophilic enamine intermediate and, in parallel, the transition metal activates a wide range of functionalities such as allylic substrates through the formation of reactive electrophilic π-allyl-metal complex. Since the first report of this strategy in 2006, considerable effort has been devoted to the successful advancement of this technology. In this chapter, these findings are highlighted and discussed.

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