Organic Chemistry: Current Research
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The Formation of Aromatic Carboxylic Acids from Acyl Radicals

Jeremy Albrecht^{* *}Correspondence: Jeremy Albrecht, Department of Organic Chemistry, Biochemistry and Catalysis, University of Bucharest, Bucharest, Romania, Email:

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Description

Carboxyl acids are used as acyl group radical precursors using visible-light photoredox chemical change. By the transient generation of a reactive compound intermediate, this redoxneutral approach offers a rapid entry to high-value heterocyclic compounds without the necessity of ultraviolet irradiation, high temperature, high carbon monoxide pressure, tin reagents, or peroxides. Carboxylic acids are abundant and cheap beginning materials readily available in structural diversity. For this reason, continuous efforts are created to interact with this category of compounds in novel catalytic organic transformations. The visible-light photoredox catalysis has emerged as a benign and powerful tool in organic synthesis, and novel strategies targeting carboxyl acids as building blocks are developed. Those strategies depend on the photo-induced reaction of carboxylates to generate, once carbon dioxide gas extrusion, reactive alkyl radical intermediates [1]. Capitalizing upon the high potential of visiblelight photoredox catalysis, we tend to question whether or not carboxyl acids could be used for the generation of acyl group radicals by single-electron reduction. This might offer an unprecedented synthetic methodology that extends beyond the present routes to access acyl group radicals, which are usually characterized by harsh conditions (ultraviolet irradiation, high temperature, high Carbon monoxide pressure, tin reagents, or peroxides) or the necessity of pre-generated acyl radical precursors like telluroesters, selenoesters, and thioesters.

We pictured that transient mixed anhydride intermediates, obtained from carboxyl acids within the presence of Dimethyl Dicarbonate (DMDC) which may be engaged as aerobic quenchers of a photocatalyst to come up with the required acyl radical species, along with Carbon dioxide and methanoate because it is the only byproducts [2]. This might give carboxyl acids with orthogonal redox reactivity under photocatalytic conditions and a completely unique entry to a broader spectrum of accessible products. The 3,3-disubstituted 2-oxindoles containing the carbonyl functionality are common structural motifs in pharmaceutical and bioactive natural products. Consequently, within the past few years, the development of economical artificial strategies for the synthesis of 3,3- disubstituted 2-oxindoles has received magnified interest.

Among these, 1,2-acylarylation of methacrylamides has emerged as a very attention-grabbing approach. However, the utilization of stoichiometric amounts of external oxidants, temperature, or high-energy ultraviolet light represents the disadvantages of the procedures.

Herein we tend to report the redox-neutral approach for the visible-light-mediated while acylarylation of olefines using carboxyl acids as an acyl radical supply [3]. We explored the acylarylation reaction using benzoic acid and N-methyl-Nphenylmethacrylamide because the model substrates within the presence of the photocatalyst, DMDC, and 2,6-lutidine beneath visible-light irradiation. In distinction, a weaker reductant like [Ir(ppy)₂(dtbbpy)]+ and [Ru(bpy)₃]2+ were unable to promote the reaction. Control experiments performed within the absence of the photocatalyst, the dicarbonate, or the light supply fully obstructed any reactivity. Fine calibration of the reaction conditions provided the required product quantitatively whereas conjointly decreasing reaction time and catalyst loading [4,5]. Once di-tert-butyl dicarbonate (Boc₂O) was used rather than DMDC to generate with the corresponding mixed anhydride, only traces of desired product were found. However, upon Lewis acid activation of Boc₂O with the addition of MgCl₂ the products were obtained in high yield. Substrates bearing electron-donating groups reacted smoothly and furnished the product it yields. Electron-poor substrates reacted slower beneath the optimized conditions, and catalyst loading and reaction times were required to get smart yields. We have developed an operationally convenient visible-light photocatalytic while acylarylation of olefins using the aromatic carboxyl acids as the beginning material. The protocol presents a light and energyefficient system that offers a viable method for the generation of acyl group radicals and their use in C-C bonding reactions.

References

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