Synthesis of Quinolino[3′,4′:4,5]pyrrolo[1,2-f]phenanthridines by Regioselective Sonogashira Reaction Followed by Domino C-N Coupling/Hydroamination/C-H Arylation

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

Rapid Access to 3-Substituted Pyridines and Carbolines via a Domino, Copper-free, Palladium-Catalyzed Sonogashira Cross-Coupling/6π-Aza Cyclization Sequence

Herein, we report a one-pot, three-component method for the preparation of 3-substituted pyridines and carbolines via copper-free, palladium-catalyzed Sonogashira cross-coupling with aryl iodides, followed by 6π-aza cyclization. This arylation cross-coupling/annulation cascade provides easy access to substituted, fused pyridines from readily available substrates in good yields (67-92%) with complete selectivity.

Palladium-catalyzed highly regioselective mono and double Sonogashira cross-coupling reactions of 5-substituted-1,2,3-triiodobenzene under ambient conditions

An efficient synthesis of 2,3-diiodinated diphenylacetylene and iodinated meta-terphenylacetylene derivatives through highly regioselective mono and double Sonogashira cross-coupling reactions of 5-substituted-1,2,3-triiodobenzene is reported. Significantly, the regioselectivity of coupling reactions is exclusively performed at the terminal C-I bonds, the less sterically hindered and the most regioactive positions. The highest isolated yields were achieved from reactions of electron-poor/neutral 1,2,3-triiodoarene and electron-rich arylacetylene derivatives. The use of 2.0 equiv. of arylacetylenes in one-pot fashion afforded the iodinated meta-terphenylacetylenes in excellent site selectivity and in good isolated yields. Different functional groups were found to be suitable under optimized conditions. This report discloses the first method to synthesize hitherto unknown 2,3-diiodinated diphenylacetylenes and iodinated meta-terphenylacetylenes that is facile, highly regioselective, general in scope and produces remarkable building blocks for other chemical transformations.