Visible‐Light‐Photosensitized Aryl and Alkyl Decarboxylative Functionalization Reactions

Patra, Tuhin; Mukherjee, Satobhisha; Ma, Jiajia; Strieth‐Kalthoff, Felix; Glorius, Frank

doi:10.1002/ange.201904671

Cited by 53 publications

(20 citation statements)

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“…2a). 39,40 Likewise, the use of benzoic acid derived 2b was also not successful to overcome this issue. 41 Aiming to prevent such a decarboxylation pathway, n-pentanol derived benzophenone oxime ether 2c was next considered owing to its computed low triplet energy (41.8 kcal mol -1 ).…”

Section: Resultsmentioning

confidence: 99%

“…Tetrasubstituted alkenes were however found to be unreactive. Subsequently, the efficiency of other bifunctional reagents was evaluated with styrene (39)(40)(41)(42)(43). Notably, side products originating from 1,5-hydrogen atom transfer (HAT) by the alkoxycarbonyloxyl radical were not observed when n-hexyl and cyclohexyl based carbonate esters were used (41, 42).…”

Section: Reaction Scopementioning

confidence: 99%

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Metal-free photosensitized oxyimination of unactivated alkenes with bifunctional oxime carbonates

et al. 2021

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The 1,2-aminoalcohol motif is one of the most prevalent structural components found in high-value organic molecules including pharmaceuticals and natural products. Generally, their preparation requires pre-functionalised substrates and manipulations of one functional group at a time to achieve the desired regioisomer. Herein, we describe a metal-free photosensitisation protocol for the installation of both amine and alcohol functionalities into alkene feedstocks in a single step. This approach is enabled by the identification of oxime carbonate as a suitable bifunctional source of both oxygen-and nitrogen-centred radicals for addition across alkenes with complementary regioselectivity compared to Sharpless aminohydroxylation. Use of orthogonal protection for amine and alcohol functionalities enables direct synthetic diversifications of one functional handle without influencing the other. With the use of readily available starting materials, convergent synthesis and mild reaction conditions, this process is well suited for use in various synthetic endeavors.The vicinal aminoalcohol motif is one of the most abundant structural units in natural products, pharmaceuticals, agrochemicals and privileged ligands. [1][2][3] Synthetic routes to this motif rely typically on multistep, iterative manipulations of functional groups to introduce both amine and alcohol functionalities in their desired positions. [4][5][6] Usually transition metal-catalysed directed β-C-H functionalisation of alcohols or amines offers a synthetic alternative with the necessity of a preinstalled directing group. [7][8][9][10] Nevertheless, all these approaches involve manipulation of one functional group at a time (Fig. 1a). By comparison, aminohydroxylation of alkenes is the most straightforward yet powerful approach for the synthesis of 1-amino-2-alcohols allowing simultaneous introduction of both functionalities into the molecule in a single step, as pioneered by Sharpless. 11,12 The generality of this approach however is often plagued by poor regioselectivity and the need for N-haloamides. 13 The use of a similar concept to synthesise 2-amino-1-alcohol skeleton requires a complete regioselectivity switch and remains a challenge to date (Fig. 1b). 14,15 So far, transient N-centred radical initiated aminohydroxylation strategy has been exploited in different intramolecular cyclisation context through ingenious substrate design to generate 2-amino-1-alcohol framework. [16][17][18][19] Clearly, lack of substrate generality and intramolecular nature of these transformations obviates there widespread use. In this regard, Yoon has elegantly utilized high strain of oxaziridine ring in aminal synthesis with analogous regioselectivity. [20][21][22] However, the requirement for initial radical attack by the alkene substrate to the copper-activated oxaziridine limits the use of unactivated alkenes in this aminohydroxylation approach. Alternatively, a two-step aziridination of alkene followed by nucleophilic ring opening can also deliver a similar regiosel...

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Section: Resultsmentioning

confidence: 99%

Section: Reaction Scopementioning

confidence: 99%

Metal-free photosensitized oxyimination of unactivated alkenes with bifunctional oxime carbonates

et al. 2021

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“…Compound II (1 mmol), compound III (1.2 mmol), 4‐dimethylaminopyridine (0.12 mmol), 1‐ethyl‐3(3‐dimethylpropylamine) carbodiimide (2.5 mmol) and dichloromethane (15 ml) were mixed in a round‐bottomed flask and left to react at room temperature for 12 h. The solvent was then removed under reduced pressure, and the crude product was purified using column chromatography on silica gel to give the target compounds IV , which are shown in Table 2 36–39 …”

Section: Methodsmentioning

confidence: 99%

Design, synthesis, and herbicidal activity of novel phenoxypyridine derivatives containing natural product coumarin

Zhao

Wang

Peng

et al. 2021

Pest Management Science

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BACKGROUND In recent years, protoporphyrinogen oxidase (PPO, EC 1.3.3.4) inhibitors have been widely studied as important agricultural herbicides. Our research focused on the design and synthesis of novel PPO inhibitor herbicides, through linking of a diphenylether pyridine bioisostere structure to substituted coumarins, which aims to enhance environmental and crop safety while retaining high efficacy. RESULTS A total of 21 compounds were synthesized via acylation reactions and all compounds were characterized using infrared, 1H NMR, 13C NMR, and high‐resolution mass spectra. The respective configurations of compounds IV‐6 and IV‐12 were also confirmed using single crystal X‐ray diffraction. The bioassay results showed that the title compounds displayed notable herbicidal activity, particularly compound IV‐6 which displayed better herbicidal activity in greenhouse and field experiments, crop selectivity and safety for cotton and soybean compared with the commercial herbicide oxyfluorfen. CONCLUSION The work revealed that compound IV‐6 deserves further attention as a candidate structure for a novel and safe herbicide. © 2021 Society of Chemical Industry.

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“…Several protocols for the decarboxylative and decarbonylative iodination of aryl carboxylic acids have been developed since the initial report of the Hunsdiecker reaction [22–24] . However, current reactions still exhibit several drawbacks: they either require preactivation of the carboxylic acid, [23b] stoichiometric amounts of transition metal, [23c,d] or a tailor‐made Ir‐photocatalyst for the installation of the carbon−iodine bond [23b,e] . In addition, several reports show limited substrate scope, [23f,g] or afford the desired aryl iodides in only modest yields [23h] .…”

Section: Introductionmentioning

confidence: 99%

Palladium‐Catalyzed Decarbonylative Iodination of Aryl Carboxylic Acids Enabled by Ligand‐Assisted Halide Exchange

et al. 2021

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We report an efficient and broadly applicable palladium-catalyzed iodination of inexpensive and abundant aryl and vinyl carboxylic acids via in situ activation to the acid chloride and formation of a phosphonium salt. The use of 1iodobutane as iodide source in combination with a base and a deoxychlorinating reagent gives access to a wide range of aryl and vinyl iodides under Pd/Xantphos catalysis, including complex drug-like scaffolds. Stoichiometric experiments and kinetic analysis suggest a unique mechanism involving CÀP reductive elimination to form the Xantphos phosphonium chloride, which subsequently initiates an unusual halogen exchange by outer sphere nucleophilic substitution.

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Visible‐Light‐Photosensitized Aryl and Alkyl Decarboxylative Functionalization Reactions

Cited by 53 publications

References 65 publications

Metal-free photosensitized oxyimination of unactivated alkenes with bifunctional oxime carbonates

Metal-free photosensitized oxyimination of unactivated alkenes with bifunctional oxime carbonates

Design, synthesis, and herbicidal activity of novel phenoxypyridine derivatives containing natural product coumarin

Palladium‐Catalyzed Decarbonylative Iodination of Aryl Carboxylic Acids Enabled by Ligand‐Assisted Halide Exchange

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