Palladium-Catalyzed Selective α-Arylation of ortho-Bromoacetophenones

Jonnada Krishna,Alavala Gopi Krishna Reddy,Gedu Satyanarayana

doi:10.1080/00397911.2014.880789

Jonnada Krishna, Alavala Gopi Krishna Reddy + Show 1 more

Open Access

https://doi.org/10.1080/00397911.2014.880789

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Abstract

Synthesis of 1-(2-bromophenyl)-2-phenylethanones via an intermolecular Pd-catalyzed α-arylation of 1-(2-bromophenyl)ethanones is presented. The method relies on selective C-H activation (α-arylation) of relatively more reactive external iodo-arenes as coupling partners without affecting the bromo-substituent. Moreover, the scope and generality of the method has been well studied by employing the reaction with iodo-arenes as coupling partners bearing electron-withdrawing, simple, and electron-donating groups on the aromatic ring.

Highlights

Synthetic organic chemistry has always faced the challenge of developing sustainable methods
In an extension to our ongoing research passion on transition-metal catalysis,[10] in domino one-pot,[10f,g] domino sequential one-pot[10d,e] processes,we recently reported a novel domino Pd-catalysis for the synthesis of novel 7-Methyl-5H-dibenzo[a,c][7]annulen-5-ones,[10g] we present selective arylation of 1-(2-bromophenyl)ethanones using external iodo-arenes without affecting the bromosubstituent of 1-(2-bromophenyl)ethanones (Scheme 1)
When Pd-catalysis of 1b was explored with the external halobenzenes (2a, 2e & 6g) as the coupling partners, it did not deliver the expected fused cyclic system (5ba & 5be) via bi-aryl formation followed by intramolecular Buchwald-Hartwig coupling, rather, impeded just after -arylation stage and gave the ketones (3ba & 3be)

Summary

Introduction

Synthetic organic chemistry has always faced the challenge of developing sustainable methods. Classical arylation of ketones follow the nucleophilic aromatic substitution reaction of a stabilized enolate on the aryl halide. In this regard Buchwald and Hartwig contributed a core part and developed various unusual and active palladium catalytic systems, by means of synthesizing diverse sterically hindered alkyl and electron-rich phosphine ligands for the selective -arylation8 of ketones.

Results

Conclusion