Photocatalytic Dehydrogenative Lactonization of 2-Arylbenzoic Acids
Nieves P Ramirez1, Irene Bosque1, Jose C Gonzalez-Gomez1
1Departamento de Química Orgánica, Facultad de Ciencias and Instituto de Síntesis Orgánica (ISO), Universidad de Alicante , Apdo. 99, 03080 Alicante, Spain.
Abstract:
A metal-free dehydrogenative lactonization of 2-arylbenzoic acids at room temperature was developed. This work illustrates the first application of visible-light photoredox catalysis in the preparation of benzo-3,4-coumarins, an important structural motif in bioactive molecules. The combination of photocatalyst [Acr(+)-Mes] with (NH4)2S2O8 as a terminal oxidant provides an economical and environmentally benign entry to different substituted benzocoumarins. Preliminary mechanistic studies suggest that this reaction most likely occurs through a homolytic aromatic substitution pathway.
Related Concept Videos
Reactions of Aldehydes and Ketones: Baeyer–Villiger Oxidation
The carbonyl center is activated by...
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Preparation of Carboxylic Acids: Overview
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Acid Halides to Carboxylic Acids: Hydrolysis
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic...
Acid-Catalyzed Aldol Addition Reaction


