Synthesis and Rh-catalyzed reductive cyclization of 1,6-enynes and 1,6-diynes containing alkynylboronate termini

Recent Trends in Group 9 Catalyzed C–H Borylation Reactions: Different Strategies To Control Site-, Regio-, and Stereoselectivity

Organoboron compounds continue contributing substantially to advances in organic chemistry with their increasing role as both synthetic intermediates and target compounds for medicinal chemistry. Particularly attractive methods for their synthesis are based on the direct borylation of C–H bonds of available starting materials since no additional pre-functionalization steps are required. However, due to the high abundance of C–H bonds with similar reactivity in organic molecules, synthetically useful C–H borylation protocols demand sophisticated strategies to achieve high regio- and stereoselectivity. For this purpose, selective transition-metal-based catalysts have been developed, with group 9 centered catalysts being among the most commonly utilized. Recently, a multitude of diverse strategies has been developed to push the boundaries of C–H borylation reactions with respect to their regio- and enantioselectivity. Herein, we provide an overview of approaches for the C–H borylation of arenes, alkenes, and alkanes based on group 9 centered catalysts with a focus on the recent literature. Lastly, an outlook is given to assess the future potential of the field.

1 Introduction

1.1 Mechanistic Considerations

1.2 Selectivity Issues in C–H Borylation

1.3 Different Modes of Action Employing Directing Group Strategies in C–H Borylation

1.4 Scope and Aim of this Short Review

2 Trends in C–H Borylation Reactions

2.1 Photoinduced Catalysis

2.2 Transfer C–H Borylation

2.3 Lewis Acid Mediated C–H Borylation

2.4 Directed Metalation

2.5 Miscellaneous C–H Borylation Reactions

2.6 Electrostatic Interactions

2.7 Hydrogen Bonding

3 Conclusion and Outlook

Synthesis and reactivity of alkynyl boron compounds

Over the last century, there have been considerable developments in organoboron chemistry due to the stability, non-toxicity, and easy commercial availability of various boronic esters. Several organoboron reagents have emerged and play an increasingly important role in everyday organic synthesis. Among them, alkynyl boron compounds have attracted significant attention due to their easy synthesis and diverse reactivity. In this review, we summarize the advancement of research on alkynyl boron compounds, highlighting their importance in the synthesis of valuable compounds.

Using Catalysts To Make Catalysts: Titanium-Catalyzed Hydroamination To Access P,N-Ligands for Assembling Catalysts in One Pot

Using a diamido-bis(amidate) titanium precatalyst, the hydroamination of alkynylphosphines afforded phosphinoenamine products. After reduction, 2-aminophosphines are prepared in excellent yield and on gram scale. A broad variety of alkynylphosphines and primary amines with different electronic and steric features are tolerated in this sequential transformation, enabling the rapid assembly of a collection of ligands. Additionally, intermediate phosphinoenamines can be used directly as proligands for coordination to transition metals using protonolysis or salt metathesis reactions. These transformations result in easy-to-use one pot protocols to prepare metal P,N-complexes for catalysis or small molecule activation.