Investigations into the Bromination of Substituted Phenols using Diethyl Bromomalonate and Diethyl Dibromomalonate

Abstract

Substituted 4-bromophenols can be synthesised efficiently by heating the corresponding phenol in either neat diethyl bromomalonate or diethyl dibromomalonate. We discuss the regioselectivity of such reactions and comment on the scope and limitation of this procedure.

Accelerated Discovery in Photocatalysis using a Mechanism‐Based Screening Method

“…Armed with these results,w en ext sought to rationally design ap roof-of-concept transformation involving phenols as direct quenchers.U pon single-electron oxidation by an excited photocatalyst, the resulting radical cation could react further in ahalogen-transfer pathway to generate bromophenol compounds useful as feedstocks for organic synthesis. [25] An analogous visible-light-promoted phenol bromination has been previously developed although this process does not involve direct quenching by phenols. [21a] Taking as ubstrate and catalyst combination shown by the screen to result in efficient quenching, 4-methoxyphenol (Q7)w as treated with iridium(III) complex 1 (1 mol %) in the presence of dimethyl bromomalonate (9,1equiv) in acetonitrile under irradiation with visible light from blue LEDs (5 W, l max = 455 nm).…”

“…[25] An analogous visible-light-promoted phenol bromination has been previously developed although this process does not involve direct quenching by phenols. [25] An analogous visible-light-promoted phenol bromination has been previously developed although this process does not involve direct quenching by phenols.…”

New heteroatom-rich ring systems from N,N-dialkyl-N’-chlorosulfonyl chloroformamidines

“…Bromination by diethyl bromomalonate is known; 48,49 however, the present results are the first reported examples of diethyl bromomalonate and ethyl 2-bromoacetoacetate acting as brominating agents for the pyrazole ring and further highlight the considerable nucleophilicity of the C5 atom of pyrazolo-thiatriazines 40. Accordingly, a 5-bromo substituent was introduced into 40e in high yield by treatment with N-bromosuccinimide (NBS) in hot chloroform (Scheme 31).…”

Novel Spiroannulated 3-Benzofuranones. Synthesis and Inhibition of the Human Peptidyl Prolyl cis/trans Isomerase Pin1

“…Thus, phenolic ketone 10 was treated with ethyl bromomalonate in the presence of potassium carbonate and butanone, leading to 3-benzofuranone 4 in 36% yield. As a mechanistic explanation of this transformation, it is assumed that ethyl bromomalonate acts as an electrophilic brominating agent [ 10 , 11 ] that brings about the introduction of the α-bromo substituent into the ketone 10 . Under the basic conditions, a final intramolecular nucleophilic substitution leads to a ring closure.…”