Fe(OTf)3-catalysed Friedel-Crafts reaction of benzenoid arenes with α,β-unsaturated carbonyl compounds: easy access to 1,1-diarylalkanes.

Aditya Bhattacharya,Biswajit Maji,Pushpendra Mani Shukla

doi:10.1098/rsos.170748

Aditya Bhattacharya, Biswajit Maji + Show 1 more

Open Access

https://doi.org/10.1098/rsos.170748

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Abstract

A simple and efficient method for the synthesis of 1,1-diarylalkanes via the Friedel–Crafts-type alkylation reaction of electron-rich arenes with cinnamic acid ester derivatives or chalcones is reported. Iron triflate has been found to be the best catalyst for the Friedel–Crafts-type alkylation reaction with α,β-unsaturated carbonyl compounds. This reaction afforded β,β-diaryl carbonyl compounds in good yields (65–93%) and with excellent regioselectivities. Remarkably, this method is also compatible with a variety of indoles to provide 3-indolyl-aryl carbonyl compounds in excellent yields. Great efforts have been made to deduce a plausible reaction mechanism based on isotopic labelling experiments.

Highlights

Friedel–Crafts alkylated compounds are of huge importance for the chemical industry as pharmaceuticals, agrochemicals and fine chemicals [1–13]
Iron triflate has been found to be the best catalyst for the Friedel–Crafts-type alkylation reaction with α,β-unsaturated carbonyl compounds
This reaction afforded β,β-diaryl carbonyl compounds in good yields (65–93%) and with excellent regioselectivities. This method is compatible with a variety of indoles to provide 3-indolylaryl carbonyl compounds in excellent yields

Summary

Introduction

Friedel–Crafts alkylated compounds are of huge importance for the chemical industry as pharmaceuticals, agrochemicals and fine chemicals [1–13]. Three-member cyclic and reactive intermediates, such as epoxides [24–32], aziridines [33–47] and halonium ions [48–53], or other unstable intermediates [54–58] derived in situ from alkenes have been found as potential electrophiles to afford functionalized Friedel–Crafts alkylated products Another important strategy to afford 1,1diarylalkanes is Friedel–Crafts-type hydroarylation reaction with olefins. Report an environmentally benign iron triflate-catalysed Friedel–Crafts-type alkylation reaction of electron-rich benzenoid arenes with electron-deficient alkenes such as α,β-unsaturated cinnamic acid ester and chalcone derivatives (scheme 1). This reaction provides β,β-diaryl carbonyl compounds; these are interestingly found in many biologically active compounds and pharmaceuticals (figure 1).

Result and discussion

Mechanism investigation

Findings

Conclusion

48. Friedel-Crafts reactions with