ChemInform Abstract: C-C Bond Formation via C-H Bond Activation Using an in situ Generated Ruthenium Catalyst.

: Transition-metal-catalyzed C−H bond activation employing a directing group is becoming a powerful tool to access C−C or C−hetero bond formation. Oxygen and nitrogen atoms are commonly applied as the electron donor for these directing groups. In contrast, there are only few studies on sulfur-containing groups, probably due to their toxicity to transition-metal catalysts. Nowadays a large amount of C−H activation reactions directed by sulfur-containing auxiliary groups have been successfully achieved. Because these groups can be facilely removed or modified in situ or in further steps, they are of great value in creative synthetic strategies. This paper reviews recent advances in the studies using thioether, thiol/thiophenol/disulfide, sulfoxide, and thiocarbonyl as directing groups for intermolecular C−H functionalizations as well as intramolecular oxidative annulations.

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Imine as a Linchpin Approach for Distal C(sp2)–H Functionalization

10.26434/chemrxiv.11521827 ◽

2020 ◽

Author(s):

Sukdev Bag ◽

Sadhan Jana ◽

Sukumar Pradhan ◽

Suman Bhowmick ◽

Nupur Goswami ◽

...

Keyword(s):

Organic Molecules ◽

Bond Activation ◽

Bond Formation ◽

Ancillary Ligand ◽

Significant Challenge ◽

Site Selectivity ◽

Directing Group ◽

Covalently Linked ◽

Complex Organic ◽

Post Functionalization

Despite the widespread applications of C–H functionalization, controlling site selectivity remains a significant challenge. Covalently attached directing group (DG) served as an ancillary ligand to ensure proximal ortho-, distal meta- and para-C-H functionalization over the last two decades. These covalently linked DGs necessitate two extra steps for a single C–H functionalization: introduction of DG prior to C–H activation and removal of DG post-functionalization. We introduce here a transient directing group for distal C(sp2)-H functionalization via reversible imine formation. By overruling facile proximal C-H bond activation by imine-N atom, a suitably designed pyrimidine-based transient directing group (TDG) successfully delivered selective distal C-C bond formation. Application of this transient directing group strategy for streamlining the synthesis of complex organic molecules without any necessary pre-functionalization at the distal position has been explored.

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Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

10.26434/chemrxiv.7138088.v2 ◽

2018 ◽

Author(s):

Mohit Kapoor ◽

Pratibha Chand-Thakuri ◽

Michael Young

Keyword(s):

Carbon Dioxide ◽

Transition Metal ◽

Bond Activation ◽

Bond Formation ◽

Carbon Bond ◽

Chelate Effect ◽

Free Amine ◽

Carbon Carbon Bond ◽

New Strategy ◽

Metal Catalyzed

Carbon-carbon bond formation by transition metal-catalyzed C–H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of ortho-arylbenzylamines, however, effective ortho-C–C bond formation from C–H bond activation of free primary and secondary benzylamines using PdII remains an outstanding challenge. Presented herein is a new strategy for constructing ortho-arylated primary and secondary benzylamines mediated by carbon dioxide (CO2). The use of CO2 is critical to allowing this transformation to proceed under milder conditions than previously reported, and that are necessary to furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, a chelate effect is demonstrated to facilitate selective monoarylation.

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Peptide Modifications: Versatile Tools in Peptide and Natural Product Syntheses

Synlett ◽

10.1055/s-0037-1612417 ◽

2019 ◽

Vol 30 (11) ◽

pp. 1289-1302 ◽

Cited By ~ 4

Author(s):

Phil Servatius ◽

Lukas Junk ◽

Uli Kazmaier

Keyword(s):

Amino Acids ◽

Natural Product ◽

Bond Activation ◽

Bond Formation ◽

Side Chain ◽

Peptide Backbone ◽

Claisen Rearrangements ◽

The Past ◽

Allylic Alkylations ◽

Peptide Modifications

Peptide modifications via C–C bond formation have emerged as valuable tools for the preparation and alteration of non-proteinogenic amino acids and the corresponding peptides. Modification of glycine subunits in peptides allows for the incorporation of unusual side chains, often in a highly stereoselective manner, orchestrated by the chiral peptide backbone. Moreover, modifications of peptides are not limited to the peptidic backbone. Many side-chain modifications, not only by variation of existing functional groups, but also by C–H functionalization, have been developed over the past decade. This account highlights the synthetic contributions made by our group and others to the field of peptide modifications and their application in natural product syntheses.1 Introduction2 Peptide Backbone Modifications via Peptide Enolates2.1 Chelate Enolate Claisen Rearrangements2.2 Allylic Alkylations2.3 Miscellaneous Modifications3 Side-Chain Modifications3.1 C–H Activation3.1.1 Functionalization via Csp3–H Bond Activation3.2.2 Functionalization via Csp2–H Bond Activation3.2 On Peptide Tryptophan Syntheses4 Conclusion

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