Chemoselective Suzuki-cross coupling reactions of 5-bromoquinolin-8-yl trifluoromethanesulfonate

Cross-Coupling Reactions of Polyhalogenated Heterocycles

Palladium-catalyzed cross-coupling reactions of polyhalogenated heterocycles provide a convenient access to multifold arylated and alkynylated ring systems with a broad spectrum of physical and medicinal properties. Products include thiophenes, selenophenes, pyrroles, indoles, furans, benzofurans, pyrazoles, pyridines, quinolines, pyrimidines, pyrazines, naphthyridines, quinoxalines, and others. The regioselectivity of the coupling reactions is controlled by a combination of electronic and steric parameters. While a number of couplings can be carried out essentially under standard conditions, others require the use of more sophisticated ligands and a thorough optimization of the conditions, such as solvent, temperature, or reaction time. The present Account provides a personalized overview of coupling reactions of polyhalogenated heterocycles.

1 Introduction

2 Thiophenes

3 Selenophenes

4 Pyrroles and Indoles

5 Furans and Benzofurans

6 Pyrazoles

7 Pyridines

8 Quinolines

9 Pyrimidines and Pyrazines

10 Naphthyridines and Quinoxalines

11 Miscellaneous

12 Conclusions

Some mechanistic aspects regarding the Suzuki-Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

Background: Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. ortho-Substituted arylpyridines are an important group of them. A regio- and atropselective Suzuki–Miyaura cross-coupling reaction on 3,4,5-tribromo-2,6-dimethylpyridine was studied.

Results: Reactions with various amounts of ortho-substituted phenylboronic acids with 3,4,5-tribromo-2,6-dimethylpyridine gave a series of mono- di- and triarylpyridine derivatives which allowed to draw conclusions about the order of substitution. Also, the observed selectivity in the case of ortho-methoxyphenylboronic acid suggested an additional metal O-chelation effect in the transition state, apparently not present in the ortho-chloro analogues. The rotational barrier in selected atropisomers was determined on the basis of HT NMR and thermal epimerisation experiments. The structure of most presented atropisomeric derivatives of 2,6-dimethylpyridine was confirmed by single-crystal X-ray analysis. Racemic chiral, differently substituted atropisomers were also examined by ¹H NMR spectroscopy in the presence of a chiral solvating agent.

Conclusion: This regio- and atropselectivity may be generally applicable to other arylpyridine systems. A regio- and atropselective Suzuki–Miyaura cross-coupling process has been observed, giving an efficient access to a class of atropisomeric compounds. An opposite selectivity using a differently ortho-substituted phenylbornic acid was observed.

Chemoselective synthesis and biological evaluation of arylated 2-(Trifluoromethyl) quinolines as nucleotide pyrophosphatase (NPPs) inhibitors

A new approach to arylated 2-trifluoromethylquinolines based on novel regioselective Suzuki-Miyaura coupling reactions has been developed. Moreover, site-selective, chemo-selective amination reactions were performed. The new 2-trifluoromethylquinoline derivatives were tested as potential NPPs inhibitors and evaluated for their potential to inhibit two families of ecto-nucleotidases, i.e. NPPs and nucleoside triphosphate diphosphohydrolases (NTPDases). Several derivatives were active on a nanomolecular concentration. The results were validated based on docking studies to study the active binding site of the molecules.

Rapid Room-Temperature, Chemoselective Csp2 -Csp2 Coupling of Poly(pseudo)halogenated Arenes Enabled by Palladium(I) Catalysis in Air

While chemoselectivities in Pd⁰‐catalyzed coupling reactions are frequently non‐intuitive and a result of a complex interplay of ligand/catalyst, substrate, and reaction conditions, we herein report a general method based on Pd^I that allows for an a priori predictable chemoselective Csp2 −Csp2 coupling at C−Br in preference to C−OTf and C−Cl bonds, regardless of the electronic or steric bias of the substrate. The C−C bond formations are extremely rapid (<5 min at RT) and are catalyzed by an air‐ and moisture‐stable Pd^I dimer under open‐flask conditions.

Regioselective Suzuki couplings of non-symmetric dibromobenzenes: alkenes as regiochemical control elements

The regioselective Suzuki coupling of dibromobenzenes has been investigated. The regiochemistry is high when one bromine atom is proximal to an alkene.