Functional group divergence and the structural basis of acridine photocatalysis revealed by direct decarboxysulfonylation

Nguyen, Vu Tuan; Haug, Graham C.; Nguyễn, Việt Dũng; Vuong, Ngan T. H.; Karki, Guna B.; Arman, Hadi D.; Larionov, Oleg V.

doi:10.1039/d2sc00789d

Cited by 62 publications

(37 citation statements)

References 89 publications

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“…It is also apparent that putting additional groups at the ortho ‐positions of the 9‐aryl group of the acridine would decrease this acridine deactivation pathway, thereby increasing the catalyst performance. Recently, the influence of steric and electronic effects of the C‐9 substituents on catalytic performance of an acridine was studied by Larionov [10f] …”

Section: Resultsmentioning

confidence: 99%

“…Besides apparent functional group limitations, these reactions cannot be applied to the synthesis of bulky acridines (e. g., Ar=2,6‐diisopropylphenyl). The addition of Grignard reagents to N ‐protected acridone followed by aromatization was used for the preparation of a 9‐mesitylacridine catalyst (Scheme 2B) [10f,17] . However, we failed to obtain acceptable results for the introduction of a bulkier aryl group.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and Evaluation of Sterically Hindered Acridine Photocatalysts

et al. 2022

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A practical nickel‐catalyzed protocol for the synthesis of sterically hindered 9‐arylacridines via Negishi type cross‐coupling was developed. The method enables a convenient approach to a set of active acridine photocatalysts starting from commercially available 9‐chloroacridine, inexpensive catalyst [NiCl2(Ph3P)2], and organozinc reagent with no need for additional ligands and precious metals. The synthetic protocol could be readily performed on a gram scale. The photocatalytic efficiency of obtained acridines was tested in decarboxylative thiolation and amination reactions. Structures of 19 acridines were studied by X‐ray analysis, which allowed to propose a steric descriptor relevant to the catalytic activity.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preparation and Evaluation of Sterically Hindered Acridine Photocatalysts

et al. 2022

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“…Photocatalytic direct decarboxylative functionalization has opened new directions in the synthetic methodology by enabling one-step functional group interconversions between abundant and structurally diverse carboxylic acids and other valuable functionalities without the need for preactivation of the carboxylic group. − However, photoactivation of the carboxylic group toward decarboxylation poses significant challenges with respect to the scope of the acids and the diversity of carbon–carbon and carbon–heteroatom bond-forming reactions, due to the combination of the acidity of the carboxylic group that may interfere with other catalytic processes and the resistance of acids to oxidative cleavage ( E ox > 2.0 V vs standard calomel electrode (SCE)) or O–H hydrogen atom transfer (bond dissociation energy (BDE) 112 kcal/mol) …”

Section: Introductionmentioning

confidence: 99%

“…We recently described a new class of photocatalysts for visible light-induced direct decarboxylative functionalization of carboxylic acids that enabled a one-step access to several important functionalities and provided insights into the mechanistic underpinnings of complex dual and triple catalytic systems (Scheme B) . The reaction scope of the new photocatalytic system has also recently been successfully expanded to the synthetically useful hydrazone additions and perfluoropyridinethiolation by the Dilman group .…”

Section: Introductionmentioning

confidence: 99%

Tricomponent Decarboxysulfonylative Cross-coupling Facilitates Direct Construction of Aryl Sulfones and Reveals a Mechanistic Dualism in the Acridine/Copper Photocatalytic System

et al. 2022

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Dual catalytic systems involving photocatalytic activation and transition metal-catalyzed steps have enabled innovative approaches to the construction of carbon–carbon and carbon–heteroatom bonds. However, the mechanistic complexity of the dual catalytic processes presents multiple challenges for understanding of the roles of divergent catalytic species that can impede the development of future synthetic methods. Here, we report a dual catalytic process that enables the previously inaccessible, broad-scope, direct conversion of carboxylic acids to aromatic sulfonescentrally important carbonyl group bioisosteric replacements and synthetic intermediatesby a tricomponent decarboxysulfonylative cross-coupling with aryl halides. Detailed mechanistic and computational studies revealed the roles of the copper catalysts, bases, and halide anions in channeling the acridine/copper system via a distinct dual catalytic manifold. In contrast to the halide-free decarboxylative conjugate addition that involves cooperative dual catalysis via low-valent copper species, the halide counteranions divert the decarboxysulfonylative cross-coupling with aryl halides through a two-phase, orthogonal relay catalytic manifold, comprising a kinetically coupled (via antithetical inhibitory and activating roles of the base in the two catalytic cycles), mechanistically discrete sequence of a photoinduced, acridine-catalyzed decarboxylative process and a thermal copper-catalyzed arylative coupling. The study underscores the importance of non-innocent roles of counteranions and key redox steps at the interface of catalytic cycles for enabling previously inaccessible dual catalytic transformations.

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“…Generally, strategies for the construction of these frameworks mainly focus on the fluoride–chloride exchange from the corresponding sulfonyl chlorides. 3 Other methods, including conjugate addition, 4 electrophilic fluorination of thiols, 5 anodic oxidative fluorination, 6 and SO 2 insertion/fluorination, 7 for the preparation of sulfonyl fluorides have also been reported. Compared with these methods via S–F bond formation, direct fluorosulfonylation by using FSO 2 -containing reagents represents a concise and effective approach for C–SO 2 F bond formation.…”

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confidence: 99%