A Visible Light and Iron‐mediated Carbocationic Route to Polysubstituted 1‐Halonaphthalenes by Benzannulation using Allylbenzenes and Polyhalomethanes

Abstract

A wide array of polysubstituted 1‐bromo and chloronaphthalenes are obtained from coupling of allylbenzenes and polyhalomethanes. The reaction is mediated by iron metal under visible light irradiation and proceeds via a Kharasch addition intermediate followed by intramolecular FeIII mediated Friedel‐Crafts alkylation, with the formation of two Csp2−Csp2 bonds in the process. This method gives easy access to 1‐halonaphthalenes with substituent(s) at C‐5 to C‐8 that are otherwise hard to synthesize.

Photo‐Induced Halogen‐Atom Transfer: Generation of Halide Radicals for Selective Hydrohalogenation Reactions

“…Those conditions completely inhibited the formation of compound 2 a , and two TEMPO adducts could be detected by MS analysis in both reactions (Scheme 3). Indeed, while TEMPO‐Br was not detected, [18] TEMPO‐CH 2 CH 2 Br and TEMPO‐Si(TMS) 3 were observed from the crude reaction mixtures. This result comforts the proposition that ⋅CH 2 CH 2 Br and ⋅Si(TMS) 3 radicals are generated in the medium during the reaction, which is consistent with the mechanistic proposal.…”

Visible photons as ideal reagents for the activation of coloured organic compounds

“…131 The generation of a trihalomethyl radical was also exploited in the iron(0) catalysed benzannulation of allylarenes to form 1-halonaphthalenes. 132…”

“…131 The generation of a trihalomethyl radical was also exploited in the iron(0) catalysed benzannulation of allylarenes to form 1-halonaphthalenes. 132 Umemoto's reagent 24.1 (Scheme 24) has traditionally been employed in photoredox catalysed trifluoromethylation. Recently, the possibility of generating a trifluoromethyl radical 135 The same photoactivatable substrates have been also employed in the acylation of nitrogen-based heterocycles, thioflavones 136 and benzothiazoles.…”