Palladium-catalyzed direct arylation and cyclization of o-iodobiaryls to a library of tetraphenylenes.

Chendan Zhu,Yue Zhao,Di Wang,Wei-Yin Sun,Zhuangzhi Shi

doi:10.1038/srep33131

Abstract

Aryl–aryl bond formation constitutes one of the most important subjects in organic synthesis. The recent developments in direct arylation reactions forming aryl–aryl bond have emerged as very attractive alternatives to traditional cross-coupling reactions. Here, we describe a general palladium-catalyzed direct arylation and cyclization of o-iodobiaryls to build a library of tetraphenylenes. This transformation represents one of the very few examples of C-H activation process that involves simultaneous formation of two aryl–aryl bonds. Oxygen plays a vital role by ensuring high reactivity, with air as the promoter furnished the best results. We anticipate this ligand-free and aerobic catalytic system will simplify the synthesis of tetraphenylenes as many of the reported methods involve use of preformed organometallic reagents and will lead to the discovery of highly efficient new direct arylation process.

Highlights

State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
The second possible pathway is the oxidative addition of palladacycle B with another substrate molecule to generate C, which can undergo a second C-H activation providing the spiropalladacycle D
Employing two iodoarene substrates such as o-iodobiphenyl (1a) and 1-iodo-4-methylbenzene (11) in our catalytic system, the cross-coupling and cyclization product 1251 was formed in 13% yield via intermediate C’ along with 65% yield of homo-coupling product 2aa (Fig. 7c)

Summary

Introduction

State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China. Removal of the ligand maintained the similar reactivity and afforded the desired product in 39% yield (entry 4). Raising the reaction temperature to 130 °C under air, the desired product 2a was isolated in maximum yield (86%, entry 7). The use of 2-bromo-1,1′-biphenyl (1a’) and [1,1′-biphenyl]-2-yl trifluoromethanesulfonate (1a”) as the substrates provided lower yield of the desired product 2aa (entries 8–9).

Results

Conclusion