Efficient synthesis of functionalized dibenzofurans by domino ‘twofold Heck/6π-electrocyclization’ reactions of 2,3-di- and 2,3,5-tribromobenzofuran

Recent advances in the synthesis of dibenzofurans

This review reports recent accesses to the dibenzofuran nucleus described in the literature since 2008. This article starts with synthesizing dibenzofurans by creating the C-O bond of the furan ring. In the following section, we evoke the formation of dibenzofurans by cyclizing diarylether derivatives. The last part of this update concerns the construction of dibenzofurans from benzofuran or phenol derivatives. Representative examples showing the scope of these processes illustrate new approaches and biological activities of dibenzofurans. Reaction mechanisms explaining certain dibenzofuran formation are described, as suggested by their authors.

Synthesis of Nitrogen Heterocycles by Domino C–N Coupling/Hydroamination Reactions

The present article presents a personalized Account on the synthesis of nitrogen heterocycles by domino C–N coupling/hydroamination reactions and related processes. The starting materials, 2-alkynyl-1-halohetarenes, are regioselectively available by Sonogashira reactions of various 1,2-dihalogenated heterocycles, such as thiophenes, benzothiophenes, furans and benzofurans, pyridines, quinolines, pyrimidines, and other ring systems. More complex products are formed by domino C–N coupling/hydroamination/C–H arylation reactions of 2-alkynyl-1-halohetarenes with 2-bromoanilines. In these reactions, not only two, but three bonds are formed in one step. In many cases, the products constitute new heterocyclic core structures and show interesting pharmacological or fluorescence properties.

1 Introduction

2 Domino C–N Coupling/Hydroamination Reactions

3 Domino C–N Coupling/Hydroamination/C–H Arylation Reactions

4 Conclusions

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

Total synthesis of diptoindonesin G and its analogues as selective modulators of estrogen receptors

We have developed a versatile synthetic strategy for the synthesis of the natural product diptoindonesin G and its analogues as selective modulators of estrogen receptors. The strategy involves a regioselective dehydrative cyclization of arylacetals, a regioselective bromination of benzofurans, a sequential cross-coupling of bromo-benzofurans with aryl boronic acids, and a BBr₃-mediated tandem cyclization and demethylation. Preliminary biological studies uncovered the critical and dispensable phenolic hydroxyl groups in the natural product and also revealed unexpected selectivity for isoforms of estrogen receptor.

Rapid regio- and multi-coupling reactivity of 2,3-dibromobenzofurans with atom-economic triarylbismuths under palladium catalysis

A regio- and chemoselective cross-coupling study using 2,3-dibromobenzofurans and 2,3,5-tribromobenzofuran was achieved with sub-stoichiometric loadings of triarylbismuths as atom-economic reagents under Pd-catalyzed conditions. As part of this study, various 2,3-diaryl- and 2,3,5-triarylbenzofuran products were obtained in high yields, involving one-pot operations and short reaction times.

Site-Selective Suzuki-Miyaura and Sonogashira Cross Coupling Reactions of the Bis(triflate) of 2,4'-Bis(hydroxy)diphenyl Sulfone

Described is the synthesis of novel arylated and alkynylated 2,4′‐diphenyl sulfones based on what are, to the best of our knowledge, the first palladium(0)‐catalyzed cross‐coupling reactions of bis(triflates) of 2,4′‐bis(hydroxy)diphenyl sulfone. The reactions proceed with very good site‐selectivity.