Synthesis of Triborylalkenes from Terminal Alkynes by Iridium‐Catalyzed Tandem C?H Borylation and Diboration

A two‐step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B₂pin₂.     

Copper‐Catalyzed Regioselective ortho C?H Cyanation of Vinylarenes

A copper‐based catalytic technique for the regioselective ortho C H cyanation of vinylarenes has been developed. This method provides an effective means for the selective functionalization of vinylarene derivatives. A copper‐catalyzed cyanative dearomatization mechanism is proposed to account for the regiochemical course of this reaction.     

Iridium‐Catalyzed Regioselective Silylation of Aromatic and Benzylic C?H Bonds Directed by a Secondary Amine

Reported herein is an iridium‐catalyzed, regioselective silylation of the aromatic C H bonds of benzylamines and the benzylic C H bonds of 2,N‐dialkylanilines. In this process, (hydrido)silyl amines, generated in situ by dehydrogenative coupling of benzylamine or aniline with diethylsilane, undergo selective silylation at the C H bond γ to the amino group. The products of this silylation are suitable for subsequent oxidation, halogenation, and cross‐coupling reactions to deliver benzylamine and arylamine derivatives.     

Amide‐Directed Tandem C?C/C?N Bond Formation through C?H Activation

The transformation of C? H bonds into other chemical bonds is of great significance in synthetic chemistry. C? H bond‐activation processes provide a straightforward and atom‐economic strategy for the construction of complex structures; as such, they have attracted widespread interest over the past decade. As a prevalent directing group in the field of C? H activation, the amide group not only offers excellent regiodirecting ability, but is also a potential C? N bond precursor. As a consequence, a variety of nitrogen‐containing heterocycles have been obtained by using these reactions. This Focus Review addresses the recent research into the amide‐directed tandem C? C/C? N bond‐formation process through C? H activation. The large body of research in this field over the past three years has established it as one of the most‐important topics in organic chemistry.     

Iron‐Catalyzed Chemoselective ortho Arylation of Aryl Imines by Directed C?H Bond Activation

Naheliegende Alternative : Eine eisenkatalysierte Imin‐gesteuerte C‐H‐Aktivierung mit einem Diarylzinkreagens führt eine Arylgruppe in ortho‐Stellung an einem von Acetophenon abgeleiteten Imin ein (siehe Schema); mit einem Palladiumkatalysator tritt dagegen eine gewöhnliche Substitution auf. Die Titelreaktion ist eine milde C‐H‐Aktivierung, die in Gegenwart von 1,2‐Dichlorisobutan mit Arylbromiden, ‐chloriden oder ‐sulfonaten selektiv verläuft.

     

Iron‐Catalyzed Chemoselective ortho Arylation of Aryl Imines by Directed C?H Bond Activation

No Fe‐ar : Iron catalyzes an imine‐directed C? H bond activation to introduce an ortho‐aryl group to an acetophenone‐derived imine using a diarylzinc reagent (see scheme), whereas palladium catalyzes the conventional substitution reaction . The title reaction features mild and selective C? H bond activation in the presence of aryl bromide, chloride, or sulfonate groups, and 1,2‐dichloroisobutane is essential to achieve such selectivity.

     

Synthesis of Phenanthridinones from N‐Methoxybenzamides and Aryltriethoxysilanes through RhIII‐Catalyzed C?H and N?H Bond Activation

An efficient method for the one‐pot synthesis of substituted phenanthridinone derivatives from N‐methoxybenzamides and aryltriethoxysilanes through rhodium‐catalyzed dual C? H bond activation and annulation reactions is described. A double‐cycle mechanism is proposed to account for this catalytic reaction. In addition, isotope‐labeling studies were performed to understand the intimate mechanism of the reaction.     

Cobalt‐Catalyzed C?H Cyanation of Arenes and Heteroarenes

Carboxylate assistance proved to be the key for the success of efficient cobalt(III)‐catalyzed C H cyanations. Thus, an in situ generated cationic cobalt complex was identified as a versatile catalyst for the site‐selective synthesis of various aromatic and heteroaromatic nitriles with ample substrate scope.