A One‐Pot Approach for Bio‐Based Arylamines via a Combined Photooxidative Dearomatization‐Rearomatization Strategy

Abstract

The synthesis of arylamines from renewable resources under mild reaction conditions is highly desired for the sustainability of the chemical industry, where the production of hazardous waste is a prime concern. However, to date, there are very few tools in chemists’ toolboxes that are able to produce arylamines in a sustainable manner. Herein, a robust one‐pot approach for constructing bio‐based arylamines via a combined photooxidative dearomatization‐rearomatization strategy is presented. The developed methodology enables the synthesis of structurally complex amines in moderate‐to‐good isolated yields using biomass‐derived phenols, natural α‐amino acids, and naphthols under remarkably mild reaction conditions. For the photooxygenation of phenols, a novel chrysazine‐based catalyst system was introduced, demonstrating its efficiency for the synthesis of natural products – hallerone, rengyolone, and the pharmaceutically relevant prodrug DHED.

Photocatalytic Synthesis of para-Peroxyquinols: Total Synthesis of (±)-Stemenone B and (±)-Parvistilbine B

“…Their conditions used in batch also required longer reaction times . Additional photochemical and nonphotochemical methods have afforded para -quinols efficiently.…”

Aniline Derivatives from Lignin under Mild Conditions Enabled by Electrochemistry

“…[23a] Furthermore, the photooxidative dearomatization of phenols targeting the coupling with α-amino acids has been recently reported, nevertheless, this method displays low selectivity in the case of ortho-methoxy substituted phenols and also the stoichiometric use of triphenylphosphine is mandatory. [24] The dearomatization of phenols by electrochemical oxidation [25] allows a clean pathway, avoiding the use of any sacrificial reagent and only consuming electric energy, which can be potentially afforded by renewable technologies. [26] More specifically for the electrochemical oxidation of lignin-derived phenols, we envisage that the inherent functionalities might play an active role in the formation of more reactive cyclohexadienone intermediates.…”

“…In that regard, we have earlier demonstrated the synthesis of anilines via chemically‐driven oxidative dearomatization of phenols applying hypervalent iodine reagents (PIDA or PIFA) [23a] . Furthermore, the photooxidative dearomatization of phenols targeting the coupling with α‐amino acids has been recently reported, nevertheless, this method displays low selectivity in the case of ortho ‐methoxy substituted phenols and also the stoichiometric use of triphenylphosphine is mandatory [24] …”

Bridged‐Ring Skeletons from Organoaluminium‐Mediated Nucleophilic Addition‐Cyclization Sequence of p‐Quinone Monoacetals and Grignard Reagents

“…[3,4] Being long regarded as versatile intermediates with manifold reactivities, [5] these compounds recently regain much attention as "aromatic to be" surrogates in selective organic synthesis. [6][7][8] Besides, it is noteworthy that the multi-reactivities arising from the cyclic dienone functionality of p-QMAs also render these compounds promising cyclo-C 6 building blocks for the construction of various bridged-ring skeletons such as bicyclo[n. 3.1] ring systems, [9][10][11][12] analogous motifs of which are frequently encountered in bio-active small molecules, natural products as well as synthetic intermediates (Scheme 1A). [13] Previously, the groups of Aubé, Lin, Zheng, etc.…”

“…Specifically, we report here an organoaluminum-mediated nucleophilic addition-cyclization of 2siloxyphenyl-magnesium reagents with p-QMAs to provide a modular synthesis of benzo-fused 2oxabicyclo[3.3.1]nonones (Scheme 1C). During the course of this project, rewardingly, we further discovered a new conjugate-addition-dimerization sequence of p-QMAs with Grignard reagents that results in a facile and diastereoselective synthesis of a portfolio of otherwise difficultly accessible bridged-ring compounds with tricyclo[6.2.2.0 2,7 ]dodecene skeletons. We present these results here as well.…”