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Performing asymmetric cross‐coupling reactions between propargylic electrophiles and aryl nucleophiles is a well‐established method to build enantioenriched benzylic alkynes. Here, a catalytic enantioselective propargyl‐aryl cross‐coupling between two electrophiles was achieved for the first time in a stereoconvergent manner. Propargylic chlorides were treated with aryl iodides as well as heteroaryl iodides in the presence of a chiral nickel complex, and manganese metal was used as a stoichiometric reductant, allowing for the construction of a propargyl C‐aryl bond under mild conditions. An alternative dual nickel/photoredox catalytic protocol was also developed for this cross‐electrophile coupling in the absence of a metal reductant. The potential utility of this conversion is demonstrated in the facile construction of stereoenriched bioactive molecule derivatives and medicinal compounds based on the diversity of acetylenic chemistry. Detailed experimental studies have revealed the key mechanistic features of this transformation. [ABSTRACT FROM AUTHOR]

Enamides, functional derivatives of enamines, play a significant role as synthetic targets. However, the stereoselective synthesis of these molecules has posed a longstanding challenge in organic chemistry, particularly for acyclic enamides that are less thermodynamically stable. In this study, we present a general strategy for constructing β‐borylenamides by C−H borylation, which provides a versatile platform for generating the stereodefined enamides. Our approach involves the utilization of metalloid borenium cation, generated through the reaction of BBr3 and enamides in the presence of two different additives, avoiding any exogenous catalyst. Importantly, the stereoconvergent nature of this methodology allows for the use of starting materials with mixed E/Z configurations, thus highlighting the unique advantage of this chemistry. Mechanistic investigations have shed light on the pivotal roles played by the two additives, the reactive boron species, and the phenomenon of stereoconvergence. [ABSTRACT FROM AUTHOR]

Hemilabile ligands have been applied extensively in transition metal catalysis, but preparations of these molecules typically require multistep synthesis. Here, modular assembly of diverse phosphine‐amide ligands, including related axially chiral compounds, is first reported through ruthenium‐catalyzed C−H activation of phosphines with isocyanate directed by phosphorus(III) atoms. High reactivity and regioselectivity can be obtained by using a Ru3(CO)12 catalyst with a mono‐N‐protected amino acid ligand. This transformation significantly expands the pool of phosphine‐amide ligands, some of which have shown excellent efficiency for asymmetric catalysis. More broadly, the discovery constitutes a proof of principle for facile construction of hemilabile ligands directly from the parent monodentate phosphines by C−H activation with ideal atom, step and redox economy. Several dinuclear ruthenium complexes were characterized by single‐crystal X‐ray diffraction analysis revealing the key mechanistic features of this transformation. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed C−H activation is a step‐economical strategy for peptide functionalization. Herein, we report the method of late‐stage peptide ligation and macrocyclization through rhodium‐catalyzed alkylation of tryptophan residues at the C7 position. This method utilizes a N‐PtBu2 directing group and tolerates various peptide and alkene substrates. Utilizing internal olefins, this study represents the first example of site‐selective peptide C−H alkylation through deconjugative isomerization. Furthermore, our method provides access to peptide macrocycles with unique Trp(C7)‐alkyl crosslinks and potent cytotoxicity towards cancer cells. [ABSTRACT FROM AUTHOR]

Stereo‐ and enantioselective cross‐electrophile coupling involving C−F bond activation is reported. Treatment of gem‐difluoroalkenes with racemic benzyl electrophiles in the presence of a chiral nickel complex using B2pin2 as a stoichiometric reductant allows the construction of a C(sp2)−C(sp3) bond under mild conditions, affording a broad range of monofluoroalkenes bearing stereogenic allylic centers. Initial mechanistic studies indicate that a radical chain pathway may be operating, wherein the ester group in the gem‐difluoroalkene promotes C−F bond activation through oxidative addition to a Ni species. [ABSTRACT FROM AUTHOR]

An efficient method for photocatalytic perfluoroalkylation of vinyl‐substituted all‐carbon quaternary centers involving 1,2‐aryl migration has been developed. The rearrangement reactions use fac‐Ir(ppy)3, visible light and commercially available fluoroalkyl halides and can generate valuable multisubstituted perfluoroalkylated compounds in a single step that would be challenging to prepare by other methods. Mechanistically, the photoinduced alkyl radical addition to an alkene leads to the migration of a vicinal aryl substituent from its adjacent all‐carbon quaternary center with the concomitant generation of a C‐radical bearing two electron‐withdrawing groups that is further reduced by a hydrogen donor to complete the domino sequence. [ABSTRACT FROM AUTHOR]

The first aromatic C−H silylation between arylphosphines and hydrosilanes enabled by a ruthenium complex has been developed. The excellent ortho‐selectivity results from a four‐membered metallacyclic intermediate involving phosphorus chelation. The developed system can be extended to the benzylic C−H silylation of arylphosphines. Diverse silylated arylphosphines are produced, exhibiting broad functional group compatibility. Further functionalization of the products under mild conditions renders the formed compounds useful building blocks. [ABSTRACT FROM AUTHOR]

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Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)