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Evidence for the Generation of α-Carboxy-α-hydroxy-p-xylylene from p-(Bromomethyl)mandelate by Mandelate Racemase
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Lin, David T.,Powers, Vincent M.,Reynolds, Laure J.,Whitman, Christian P.,Kozarich, John W.,Kenyon, George L.
p. 323 - 326
(1988)
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Rapid assembly of α-ketoamides through a decarboxylative strategy of isocyanates with α-oxocarboxylic acids under mild conditions
A simple and practical method for α-ketoamide synthesis via a decarboxylative strategy of isocyanates with α-oxocarboxylic acids is described. The reaction proceeds at room temperature under mild conditions without an oxidant or an additive, showing good substrate scope and functional compatibility. Moreover, the applicability of this method was further demonstrated by the synthesis of various bioactive molecules and different application examples through a two-step one-pot operation.
Huang, Junjie,Liang, Baihui,Chen, Xiuwen,Liu, Yifu,Li, Yawen,Liang, Jingwen,Zhu, Weidong,Tang, Xiaodong,Li, Yibiao,Zhu, Zhongzhi
supporting information
p. 4783 - 4787
(2021/06/11)

Photoinduced homolytic decarboxylative acylation/cyclization of unactivated alkenes with α-keto acid under external oxidant and photocatalyst free conditions: access to quinazolinone derivatives
A novel and green strategy for the synthesis of acylated quinazolinone derivativesviaphoto-induced decarboxylative cascade radical acylation/cyclization of quinazolinone bearing unactivated alkenes has been developed. The protocol provides a novel route to access acyl radicals from α-keto acids through a self-catalyzed energy transfer process. Most importantly, the reaction proceeded smoothly without any external photocatalyst, additive or oxidant, and could be easily scaled-up in flow conditions with sunlight irradiation.
Sun, Bin,Shi, Rongcheng,Zhang, Kesheng,Tang, Xiaoli,Shi, Xiayue,Xu, Jiayun,Yang, Jin,Jin, Can
supporting information
p. 6050 - 6053
(2021/06/21)

Hypervalent Iodine(III)-Promoted Radical Oxidative C-H Annulation of Arylamines with α-Keto Acids
A novel catalyst-free radical oxidative C-H annulation reaction of arylamines with α-keto acids toward benzoxazin-2-ones synthesis under mild conditions was developed. This hypervalent iodine(III)-promoted process eliminated the use of a metal catalyst or additive with high levels of functional group tolerance. Hypervalent iodine(III) was both an oxidant and a radical initiator for this reaction. The synthetic utility of this method was confirmed by the synthesis of the natural product cephalandole A.
Long, Lipeng,Wang, Jieyan,Gu, Liuqing,Yang, Shiguang,Qiao, Liang,Luo, Guotian,Chen, Zhengwang
supporting information
p. 12084 - 12092
(2021/08/24)

Possible competitive modes of decarboxylation in the annulation reactions ofortho-substituted anilines and arylglyoxylates
Annulation reactions ofortho-substituted anilines and arylglyoxylates in the presence of K2S2O8at 80 °C under metal-free neutral conditions have been investigated, which extended a platform for the tandem synthesis of nitrogen heterocycles. While arylglyoxylic acids are known to undergo decarboxylation to form an acyl radical in the presence of K2S2O8and used in the Minisci acylation of electron-deficient (hetero)aromatics, their reactions with electron-richortho-substituted anilines to form nitrogen heterocycles have recently been studied. Depending upon the experimental conditions used in the reactions, the mechanism of the formation of heterocycles involving reactions of an acyl radical or aryl iminocarboxylic acids has been postulated. Given the subtle understanding of the mechanisms of annulation reactions of 2-substituted anilines and arylglyoxylates in the presence of K2S2O8, an extensive mechanistic investigation was undertaken. In the current study, the various mechanistic pathways including the generation of acyl, imidoyl, aminal, and N,O-hemiketal radicals have been postulated based on different possible decarboxylation modes. Some of the proposed intermediates are supported based on the available analytical data. The protocol uses a single, inexpensive reagent K2S2O8, which offers not only transition-metal-free conditions but also serves as the reagent for the key decarboxylation step. Taken together, this study complements the current development of the annulation reactions of 2-substituted anilines and arylglyoxylates in terms of synthesis and mechanistic understanding.
Laha, Joydev K.,Panday, Surabhi,Tomar, Monika,Patel, Ketul V.
supporting information
p. 845 - 853
(2021/02/09)

Direct 1,2-Dicarbonylation of Alkenes towards 1,4-Diketones via Photocatalysis
1,4-Dicarbonyl compounds are intriguing motifs and versatile precursors in numerous pharmaceutical molecules and bioactive natural compounds. Direct incorporation of two carbonyl groups into a double bond at both ends is straightforward, but also challenging. Represented herein is the first example of 1,2-dicarbonylation of alkenes by photocatalysis. Key to success is that N(n-Bu)4+ not only associates with the alkyl anion to avoid protonation, but also activates the α-keto acid to undergo electrophilic addition. The α-keto acid is employed both for acyl generation and electrophilic addition. By tuning the reductive and electrophilic ability of the acyl precursor, unsymmetric 1,4-dicarbonylation is achieved for the first time. This metal-free, redox-neutral and regioselective 1,2-dicarbonylation of alkenes is executed by a photocatalyst for versatile substrates under extremely mild conditions and shows great potential in biomolecular and drug molecular derivatization.
Chen, Bin,Cheng, Yuan-Yuan,Hou, Hong-Yu,Lei, Tao,Tung, Chen-Ho,Wu, Li-Zhu,Yu, Ji-Xin
supporting information
p. 26822 - 26828
(2021/11/17)

Visible-Light-Promoted Switchable Synthesis of C-3-Functionalized Quinoxalin-2(1H)-ones
A visible-light-promoted synthesis of quinoxalin-2(1H)-ones has been developed using 9-mesityl-10-methylacridinium perchlorate as an organo-photocatalyst. The atmosphere-controlled method (Ar/air) enabled the selective synthesis of hydroxyl- and acyl-containing quinoxalin-2(1H)-ones under mild reaction conditions without the use of any metal catalysts or toxic reagents. A fluorescent labelling experiment showed that hydroxyl-containing quinoxalin-2(1H)-ones may have utility in various biological applications as potent fluorophores. (Figure presented.).
Aganda, Kim Christopher C.,Hong, Boseok,Lee, Anna
supporting information
p. 1443 - 1448
(2021/01/26)

K2S2O8mediated synthesis of 5-Aryldipyrromethanes and meso-substituted A4-Tetraarylporphyrins
The synthesis of dipyrromethanes from pyrrole and arylglyoxylic acids in the presence of K2S2O8at 90 C is reported affording dipyrromethanes in very good yields. Unlike an excess pyrrole traditionally used in dipyrromethane synthesis, the current method uses a stoichiometric amount of pyrrole avoiding any use of Br?nsted or Lewis acid. A gram scale synthesis of 5-phenyldipyrromethane is also achieved demonstrating potential scale up of dipyrromethanes using this method feasible. Subsequently, dipyrromethanes were converted to A4tetraarylporphyrins also in the presence of K2S2O8at 90C. A direct synthesis of A4-tetraphenylporphyrin from excess pyrrole and phenylglyoxylic acid in the presence of K2S2O8 at 90C is also reported.
Laha, Joydev K.,Hunjan, Mandeep Kaur
p. 664 - 673
(2021/06/03)

Ruthenium(II)-Catalyzed Cross-Coupling of Benzoyl Formic Acids with Toluenes: Synthesis of 2-Phenylacetophenones
Herein, we report a direct method to synthesize 2-phenylacetophenone through a ruthenium(II)-catalyzed cross-coupling reaction between acyl and benzyl radical. The various derivatives of 2-phenylacetophenone were prepared easily in moderate to good yields. These reactions provide a straightforward pathway to synthesize a variety of ketones bearing various functional groups.
Chen, Yujie,Dai, Chenyang,Huang, Zhibin,Jiang, Yaqiqi,Shu, Sai,Yang, Shan,Zhao, Yingsheng
p. 2955 - 2961
(2021/07/22)

Diazotrifluoroethyl Radical: A CF3-Containing Building Block in [3 + 2] Cycloaddition
We present herein a visible-light-induced [3 + 2] cycloaddition of a hypervalent iodine(III) reagent with α-ketoacids for the construction of 5-CF3-1,3,4-oxadiazoles that are of importance in medicinal chemistry. The reaction proceeds smoothly without a photocatalyst, metal, or additive under mild conditions. Different from the well-established trifluorodiazoethane (CF3CHN2), the diazotrifluoroethyl radical [CF3C(·)N2], a trifluoroethylcarbyne (CF3C?:) equivalent and an unusual CF3-containing building block, is involved in the present reaction system.
Zhao, Wen-Wen,Shao, Yong-Chao,Wang, An-Ni,Huang, Jia-Li,He, Chun-Yang,Cui, Bao-Dong,Wan, Nan-Wei,Chen, Yong-Zheng,Han, Wen-Yong
supporting information
p. 9256 - 9261
(2021/12/06)

Minisci aroylation of N-heterocycles using choline persulfate in water under mild conditions
Metal persulfate mediated thermal oxidative organic transformations invariably require a higher temperature and frequently use an organic solvent. The objective of this work was to develop persulfate mediated oxidative transformations that can be performed nearly at room temperature using water as a solvent. This report describes modified Minisci aroylation of isoquinolines with arylglyoxylic acids using choline persulfate and its pre-composition (choline acetate and K2S2O8) in water at 40 °C. A few other nitrogen heterocycles were also utilized affording various aroylated products in good to excellent yields. Unlike metal persulfate that could produce metal salt byproducts, a key feature of the chemistry reported herein includes the use of environmentally benign choline persulfate containing biodegradable choline as a counter-cation, the Minisci reaction demonstrated at 40 °C in water as the only solvent, and unconventional activation of persulfate. This journal is
Hunjan, Mandeep Kaur,Laha, Joydev K.,Tinwala, Ummehani
p. 22853 - 22859
(2021/12/24)

Visible-Light-Induced Catalyst-Free Carboxylation of Acylsilanes with Carbon Dioxide
Intermolecular carbon-carbon bond formation between acylsilanes and carbon dioxide (CO2) was achieved by photoirradiation under catalyst-free conditions. In this reaction, siloxycarbenes generated by photoisomerization of the acylsilanes added to the C═O bond of CO2 to give α-ketocarboxylates, which underwent hydrolysis to afford α-ketocarboxylic derivatives in good yields. Control experiments suggest that the generated siloxycarbene is likely to be from the singlet state (S1) of the acylsilane and the addition to CO2 is not in a concerted manner.
Fan, Zhengning,Yi, Yaping,Chen, Shenhao,Xi, Chanjuan
supporting information
p. 2303 - 2307
(2021/04/05)

Silyl Cyanopalladate-Catalyzed Friedel-Crafts-Type Cyclization Affording 3-Aryloxindole Derivatives
3-Aryloxindole derivatives were synthesized through a Friedel-Crafts-type cyclization. The reaction was catalyzed by a trimethylsilyl tricyanopalladate complex generated in situ from trimethylsilyl cyanide and Pd(OAc) 2. Wide varieties of diethyl phosphates derived from N -arylmandelamides were converted almost quantitatively into oxindoles. When N, N -dibenzylamide was used instead of an anilide substrate, a benzo-fused δ-lactam was obtained. An oxindole product was subjected to substitution reactions to afford 3,3-diaryloxindoles with two different aryl groups.
Ece, Hamdiye,Tange, Yuji,Yurino, Taiga,Ohkuma, Takeshi
p. 935 - 939
(2021/02/22)

Synthesis of α-Keto Acids via Oxidation of Alkenes Catalyzed by a Bifunctional Iron Nanocomposite
An efficient methodology for synthesis of α-keto acids via oxidation of alkenes using TBHP as oxidant catalyzed by a bifunctional iron nanocomposite has been established. A variety of alkenes with different functional groups were smoothly oxidized into their corresponding α-keto acids in up to 80% yield. Moreover, the bifunctional iron nanocomposite catalyst showed outstanding catalytic stability for successive recycles without appreciable loss of activity.
Song, Tao,Ma, Zhiming,Wang, Xiaoxue,Yang, Yong
supporting information
p. 5917 - 5921
(2021/07/31)

Iridium-catalyzed stereoselective [3+2] annulation of α-oxocarboxylic acids with 1,3-dienes
The stereoselective annulation of α-oxocarboxylic acids with 1,3-dienes proceeded in the presence of a hydroxoiridium catalyst to give α-hydroxy-γ-lactones in good yields with high 3,5-transrelative stereochemistry. The use of a chiral diene ligand for a cationic iridium complex enabled asymmetric annulation with high enantioselectivity.
Yabe, Ryota,Ebe, Yusuke,Nishimura, Takahiro
supporting information
p. 5917 - 5920
(2021/06/18)

Visible-Light-Induced Decarboxylative Cyclization/Hydrogenation Cascade Reaction to Access Phenanthridin-6-yl(aryl)methanol by an Electron Donor-Acceptor Complex
A novel and efficient visible-light-induced decarboxylative cyclization/hydrogenation cascade reaction of α-oxocarboxylic acids and 2-isocyanobiaryls has been developed. Without the need of any external photosensitizer, oxidant, and reductant, this method offers a mild and green approach for the synthesis of diverse alcohols in moderate to good yields. A mechanism indicated that an electron donor-acceptor complex-driven decarboxylation, radical addition/cyclization, and in situ photochemical reduction of ketones to alcohols could be involved in the reaction.
Shi, Wei,Ma, Fang,Li, Pinhua,Wang, Lei,Miao, Tao
p. 13808 - 13817
(2020/11/20)

Metal-free C3-H acylation of quinoxalin-2(1: H)-ones with α-oxo-carboxylic acids
Direct C3-H acylation of quinoxalin-2(1H)-ones with α-oxocarboxylic acids under thermo conditions promoted by PIDA has been achieved in a moderate to good yield in a very fast manner. Mechanistic study revealed that the reaction proceeds via a radical pro
Li, Yu,Ni, Hangcheng,Shi, Xingzi,Zhang, Xiaoning,Zhao, Fei,Zhao, Jingwei
supporting information
p. 6558 - 6563
(2020/09/04)

1D Fe3O4&at;CuSiO3 composites catalyzed decarboxylative A3-coupling for propargylamine synthesis
Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced St?ber method and subsequent hydrothermal reaction with copper ions in alkaline condition. The high content of Cu2+ as well as the unique structures of hierarchical copper silicate in the as-prepared catalysts endowed their outstanding catalytic performance. Efficient decarboxylative A3-coupling of α-keto acid, amine and alkyne was realized with the low Fe3O4&at;CuSiO3 loading. A range of propargylamines were produced in good to excellent yields under solvent-free condition. Moreover, the catalyst can be easily separated from the final organic product with an external magnet. Also, this kind of catalyst could be recycled up to six times while maintaining its activity.
Cao, Tiantian,Feng, Huangdi,Li, Huiqiong,Miao, Teng,Wang, Fang,Zhang, Min
supporting information
p. 1558 - 1563
(2020/07/30)

Aroylation of Electron-Rich Pyrroles under Minisci Reaction Conditions
The development of Minisci acylation on electron-rich pyrroles under silver-free neutral conditions has been reported featuring the regioselective monoacylation of (NH)-free pyrroles. Unlike conventional Minisci conditions, the avoidance of any acid that could result in the polymerization of pyrroles was the key to success. The umpolung reactivity of the nucleophilic acyl radical, generated in situ from arylglyoxylic acid, could help explain the mechanism of product formation with electron-rich pyrroles. Alternatively, the nucleophilic substitution of the acyl radical on the electron-deficient pyrrole radical cation is proposed.
Laha, Joydev K.,Kaur Hunjan, Mandeep,Hegde, Shalakha,Gupta, Anjali
supporting information
p. 1442 - 1447
(2020/02/22)

Photoredox Catalysis Enables Decarboxylative Cyclization with Hypervalent Iodine(III) Reagents: Access to 2,5-Disubstituted 1,3,4-Oxadiazoles
A novel approach to 2,5-disubstituted 1,3,4-oxadiazoles derivatives via a decarboxylative cyclization reaction by photoredox catalysis between commercially available α-oxocarboxylic acids and hypervalent iodine(III) reagent is described. This powerful transformation involves the coupling reaction between two different kinds of radical species and the formation of C-N and C-O bonds.
Li, Jian,Lu, Xue-Chen,Xu, Yue,Wen, Jin-Xia,Hou, Guo-Quan,Liu, Li
supporting information
p. 9621 - 9626
(2020/12/21)

Palladium-Catalyzed Decarboxylative ortho-C(sp2)?H Aroylation of N-Sulfoximine Benzamides at Room Temperature
A palladium-catalyzed method for the decarboxylative ortho C?H acylation of N-sulfoximine benzamides is developed at room temperature. The catalytic method enables easy access to various functionalized 2-aroylaromatic carboxylic acid derivatives in good isolated yields. Based on our mechanistic studies, a Pd(II)/Pd(IV) catalytic cycle that involves aroyl radical intermediate is proposed for the reaction.
Das, Prasenjit,Biswas, Promita,Guin, Joyram
supporting information
p. 920 - 925
(2020/03/04)

Long-wavelength methyl benzoylformate photoinitiator and preparation method thereof
The invention relates to the technical field of organic synthesis, and especially relates to a long-wavelength methyl benzoylformate photoinitiator and a preparation method thereof. The emission wavelength range of LED light sources used in the market at
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Paragraph 0045-0047

(2020/08/30)

Novel methyl benzoylformate photoinitiator and preparation method thereof
The invention relates to the technical field of organic synthesis, in particular to a novel methyl benzoylformate photoinitiator and a preparation method thereof. The emission wavelength range of LEDlight sources used in the market at present is 365 nm or above, while, the maximum absorption wavelength of a traditional photoinitiator MBF is 255 nm, and as a result, the wavelength of the traditional photoinitiator MBF is not matched with the emission wavelength of the LED light sources. In order to enable the maximum absorption wavelength of the MBF photoinitiator to be matched with the main emission wavelength range of the LED light sources, the invention provides the novel methyl benzoylformate photoinitiator and the preparation method thereof. The compound is obtained by condensation reaction of a carbonyl functionalized methyl benzoylformate derivative containing double alpha H and a ketone compound; the maximum absorption wavelength of the compound can reach 365 nm or above; and the compound is matched with the LED light sources used on the market and has good commercial application prospects.
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Paragraph 0038-0040; 0053-0055

(2020/09/09)

Selective photoredox decarboxylation of α-ketoacids to allylic ketones and 1,4-dicarbonyl compounds dependent on cobaloxime catalysis
A photoredox/cobaloxime co-catalyzed coupling reaction of α-ketoacids and methacrylates to obtain allylic ketones is described. Without the cobaloxime catalyst, 1,4-dicarbonyl compounds are generated. The cobaloxime catalyst enables dehydrogenation to generate the formation of new olefins. The generality, good substrate scope and mild conditions are good features in the photoredox/cobaloxime catalysis protocol, and this method will provide new opportunities for the functionalization of more olefins.
Zhang, Hong,Xiao, Qian,Qi, Xu-Kuan,Gao, Xue-Wang,Tong, Qing-Xiao,Zhong, Jian-Ji
supporting information
p. 12530 - 12533
(2020/11/02)

METHOD FOR PRODUCING BENZOYL FORMIC ACID COMPOUND AND PYRIDAZINE COMPOUND
The present invention provides an industrially-advantageous process for preparing a benzoyl formic acid compound, and an efficient process for preparing a pyridazine compound using the same process. Specifically, the present invention provides a process for preparing a compound represented by formula (2), which comprises a step (B): a step of reacting a compound represented by formula (1) with a nitrosyl sulfuric acid in water to produce the compound represented by formula (2).
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Paragraph 0098

(2020/12/18)

Arylglyoxylic acid as well as preparation method and application thereof
The invention relates to arylglyoxylic acid as well as a preparation method and application thereof, and the method comprises the following steps: carrying out hydrolysis reaction on arylglyoxylonitrile oxime as shown in a formula (I) under the catalysis of an inorganic acid to obtain arylglyoxylic acid as shown in a formula (II). The arylglyoxylic acid prepared by the preparation method is high in yield, high in product purity, simple to operate, environment-friendly and pollution-free. The arylglyoxylic acid is used as a fine chemical synthesis intermediate.
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Paragraph 0058-0062

(2021/01/15)

Synthesis of Unprotected 2-Arylglycines by Transamination of Arylglyoxylic Acids with 2-(2-Chlorophenyl)glycine
The transamination of α-keto acids with 2-phenylglycine is an effective methodology for directly synthesizing unprotected α-amino acids. However, the synthesis of 2-arylglycines by transamination is problematic because the corresponding products, 2-arylglycines, transaminate the starting arylglyoxylic acids. Herein, we demonstrate the use of commercially available l-2-(2-chlorophenyl)glycine as the nitrogen source in the transamination of arylglyoxylic acids, producing the corresponding 2-arylglycines without interference from the undesired self-transamination process.
Inada, Haruki,Shibuya, Masatoshi,Yamamoto, Yoshihiko
p. 11047 - 11059
(2020/10/12)

General Synthesis of Chiral α,α-Diaryl Carboxamides by Enantioselective Palladium-Catalyzed Cross-Coupling
A general synthesis of chiral α,α-diaryl carboxamides is developed by enantioselective cross-coupling between 2-bromo-2-aryl carboxamides and arylboronic acids, leading to a series of chiral α,α-diaryl carboxamides with various electronic properties and functionalities in moderate to excellent enantioselectivities and yields. The employment of a sterically bulky chiral P,P═O ligand L2 is critical for the reactivity and selectivity. This protocol is applied to an efficient asymmetric synthesis of a key intermediate of dopamine receptor agonist SKF 38393.
Li, Bowen,Aliyu, Muinat A.,Gao, Zhenhua,Li, Tiejun,Dong, Wei,Li, Junchen,Shi, Enxue,Tang, Wenjun
p. 4974 - 4978
(2020/07/03)

Scope and limitations of reductive amination catalyzed by half-sandwich iridium complexes under mild reaction conditions
The conversion of aldehydes and ketones to 1° amines could be promoted by half-sandwich iridium complexes using ammonium formate as both the nitrogen and hydride source. To optimize this method for green chemical synthesis, we tested various carbonyl substrates in common polar solvents at physiological temperature (37 °C) and ambient pressure. We found that in methanol, excellent selectivity for the amine over alcohol/amide products could be achieved for a broad assortment of carbonyl-containing compounds. In aqueous media, selective reduction of carbonyls to 1° amines was achieved in the absence of acids. Unfortunately, at Ir catalyst concentrations of 1 mM in water, reductive amination efficiency dropped significantly, which suggest that this catalytic methodology might be not suitable for aqueous applications where very low catalyst concentration is required (e.g., inside living cells).
Nguyen, Dat P.,Sladek, Rudolph N.,Do, Loi H.
(2020/07/15)

Method for preparing aromatic glyoxylic acid by oxidizing aromatic ethyl ketone with selenium dioxide
The invention discloses a method for preparing aromatic glyoxylic acid by oxidizing aromatic ethyl ketone with selenium dioxide. The method comprises the following steps: dissolving aromatic ethyl ketone in an alkaline organic solvent, carrying out stirri
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Paragraph 0017-0018

(2020/01/03)

Bioinspired Radical Stetter Reaction: Radical Umpolung Enabled by Ion-Pair Photocatalysis
A bioinspired, intermolecular radical Stetter reaction of α-keto acids and aldehydes is disclosed that is contingent on a formal “radical umpolung” concept. Enabled by secondary amine activation, electrostatic recognition ensures that the α-ketocarboxylic acids, which function as latent acyl radicals, are proximal to the in situ generated iminium salts. This photoactive contact ion pair is an electron donor–acceptor (EDA) complex, and undergoes facile single electron transfer (SET) and rapid decarboxylation prior to radical–radical recombination. Importantly, decarbonylation is mitigated by this strategy. The initial computational validation on which the process is predicated matches closely with experiment. Synergising organo- and photocatalysis activation principles finally expands the mechanistic and synthetic scope of the classic Stetter reaction to include α,β-unsaturated aldehydes as acceptors.
Morack, Tobias,Mück-Lichtenfeld, Christian,Gilmour, Ryan
supporting information
p. 1208 - 1212
(2019/01/04)

Copper-catalyzed coupling of anthranils and α-keto acids: Direct synthesis of α-ketoamides
Copper-catalyzed coupling of α-keto acids with anthranils is reported for the synthesis of α-ketoamides. This process involves N-O/C-O bond cleavages and C-N bond formation. Furthermore, the decarboxylation of α-keto acids can be successfully suppressed under redox-neutral conditions.
Li, Ping-Gui,Zhu, Hao,Fan, Min,Yan, Cheng,Shi, Kai,Chi, Xi-Wen,Zou, Liang-Hua
supporting information
p. 5902 - 5907
(2019/06/24)

Iron-catalyzed Minisci acylation of N-heteroarenes with α-keto acids
An efficient and mild protocol has been developed for the Minisci acylation reactions of nitrogen-containing heteroarenes with α-keto acids. Distinct from the conventional Minisci acylation conditions, the chemistry was performed using non-noble metal Fe(II), instead of expensive Ag(I) salt, as catalyst. A wide range of substrates, including aliphatic or aromatic α-keto acids, as well as various N-heteroarenes, proved to be compatible with the protocol. Scale-up experiment also demonstrates the practicality of the approach.
Wang, Xiu-Zhi,Zeng, Cheng-Chu
supporting information
p. 1425 - 1430
(2019/02/01)

Palladium-Catalyzed Primary Amine-Directed Decarboxylative Annulation of α-Oxocarboxylic Acids: Access to Indolo[1,2-a]quinazolines
An efficient protocol for the preparation of indolo[1,2-a]quinazolines via palladium-catalyzed decarboxylative annulation of indols with α-oxocarboxylic acids has been realized by using primary amine as a directing group (DG). This transformation proceeds smoothly with exclusive regioselectivity and represents an one-pot Domino synthesis of indo-lo[1,2-a]quinazolines from α-oxocarboxylic acids. (Figure presented.).
Jiang, Guangbin,Wang, Shoucai,Zhang, Jun,Yu, Jianwen,Zhang, Ziang,Ji, Fanghua
supporting information
p. 1798 - 1802
(2019/03/13)

Electrochemical synthesis of enaminones: Via a decarboxylative coupling reaction
An environmentally benign and efficient electrochemical synthesis of enaminones via a decarboxylative coupling reaction of α-keto acids using n-Bu4NI as a redox catalyst and electrolyte under constant current electrolysis in an undivided cell is reported. A broad vinyl azide substrate scope and high functional group tolerance are observed. A gram-scale reaction further demonstrates the practicability of the protocol. The results of cyclic voltammetry and control experiments indicate that I2 is likely the active species to initiate the oxidative decarboxylation via an acyl hypoiodite intermediate.
Kong, Xianqiang,Liu, Yulong,Lin, Long,Chen, Qianjin,Xu, Bo
supporting information
p. 3796 - 3801
(2019/07/31)

Pd(OAc)2-Catalyzed Asymmetric Hydrogenation of α-Iminoesters
An efficient Pd(OAc)2-catalyzed asymmetric hydrogenation of α-iminoesters was realized for the first time at 1 atm hydrogen pressure and room temperature. Pd(OAc)2, a less expensive Pd salt with low toxicity, was found to be the most suitable catalyst precursor rather than Pd(TFA)2 which is usually the catalyst of choice for homogeneous asymmetric hydrogenation. The chiral α-arylglycine fragments are widely found in many chiral products and bioactive molecules.
Chen, Jianzhong,Li, Feilong,Wang, Fang,Hu, Yawen,Zhang, Zhenfeng,Zhao, Min,Zhang, Wanbin
supporting information
p. 9060 - 9065
(2019/11/19)

Intermolecular Radical Addition to Ketoacids Enabled by Boron Activation
The intermolecular radical addition to the carbonyl group is difficult due to the facile fragmentation of the resulting alkoxyl radical. To date, the intermolecular radical addition to ketones, a valuable approach to construct quaternary carbon centers, remains a formidable synthetic challenge. Here, we report the first visible-light-induced intermolecular alkyl boronic acid addition to α-ketoacids enabled by the Lewis acid activation. The in situ boron complex formation is confirmed by various spectroscopic measurements and mechanistic probing experiments, which facilitates various alkyl boronic acid addition to the carbonyl group and prevents the cleavage of the newly formed C-C bond. Diversely substituted lactates can be synthesized from readily available alkyl boronic acids and ketoacids at room temperature merely under visible light irradiation, without any additional reagent. This boron activation approach can be extended to alkyl dihydropyridines as radical precursors with external boron reagents for primary, secondary, and tertiary alkyl radical additions. The pharmaceutically useful anticholinergic precursors are easily scaled up in multigrams under metal-free conditions in flow reactors.
Xie, Shasha,Li, Defang,Huang, Hanchu,Zhang, Fuyuan,Chen, Yiyun
p. 16237 - 16242
(2019/10/14)

Metal-, Photocatalyst-, and Light-Free Direct C-H Acylation and Carbamoylation of Heterocycles
Direct C-H acylations and carbamoylations of heterocycles can now be readily achieved without requiring any conventional metal, photocatalyst, electrocatalysis, or light activation, thus significantly improving on sustainability, costs, toxicity, waste, and simplicity of the operational procedure. These mild conditions are also suitable for gram-scale reactions and late-stage functionalizations of complex molecules, including pharmaceuticals, N,N-ligands, and light-sensitive molecules.
Westwood, Matthew T.,Lamb, Claire J. C.,Sutherland, Daniel R.,Lee, Ai-Lan
supporting information
p. 7119 - 7123
(2019/09/03)

Direct Acyl Radical Addition to 2 H-Indazoles Using Ag-Catalyzed Decarboxylative Cross-Coupling of α-Keto Acids
A direct acyl radical addition to 2H-indazoles has been achieved for the first time, where the less-aromatic quinonoid 2H-indazoles readily accepted radical species to the C-3 position. Motivated by the lack of direct acylation strategy for 2H-indazoles, the current method utilizes the radical acceptability of 2H-indazoles, discovering an ambient temperature reaction to provide facile access to a diverse array of 3-acyl-2H-indazoles with three points of structural diversification in 25%-83% yields.
Bogonda, Ganganna,Kim, Hun Young,Oh, Kyungsoo
supporting information
p. 2711 - 2715
(2018/05/22)

Visible-Light-Induced Decarboxylation Coupling/Intramolecular Cyclization: A One-Pot Synthesis for 4-Aryl-2-quinolinone Derivatives
A visible-light-induced decarboxylation coupling/intramolecular cyclization is reported. The one-pot synthesis system provides mild, efficient, and atom economical access to the synthesis of 4-aryl-2-quinolinone derivatives. It is notable that the necessa
Wang, Chenglong,Qiao, Jingyi,Liu, Xiaochong,Song, He,Sun, Zhizhong,Chu, Wenyi
p. 1422 - 1430
(2018/02/09)

Copper/Persulfate-Promoted Oxidative Decarboxylative C?H Acylation of Pyrazolones with α-Oxocarboxylic Acids: Direct Access to 4-Acylpyrazolones under Mild Conditions
A facile and efficient oxidative C?H acylation of N-substituted pyrazolones using α-oxocarboxylic acids as an acyl group source was developed. A combination of Cu(OAc)2 and K2S2O8 enables the reaction to proceed smoothly under air and provides a wide array of 4-acylpyrazolone products in moderate to excellent yields. The mechanism of this transformation is believed to proceed via a copper-induced decarboxylation to form the acyl-copper species. This method provides a convenient and useful route for a direct installation of an acyl moiety into bioactive pyrazolone derivatives, which can be further utilized in many applications. (Figure presented.).
Kittikool, Tanakorn,Thupyai, Akkharaphong,Phomphrai, Khamphee,Yotphan, Sirilata
supporting information
p. 3345 - 3355
(2018/09/10)

Silver-catalyzed Double Decarboxylative Radical Alkynylation/Annulation of Arylpropiolic Acids with α-keto Acids: Access to Ynones and Flavones under Mild Conditions
Ynones are privileged building blocks in various organic syntheses of heterocyclic derivatives due to their multifunctional nature, and flavones are an important class of natural products with a wide range of biological activities. We describe the catalytic double decarboxylative alkynylation of arylpropiolic acids with α-keto acids. With Ag(I)/persulfate as the catalysis system, the valuable ynones bearing various substituents could be easily obtained. The introduction of hydroxyl substituent on ortho-site of α-keto acids make this strategy further applicable to the construction of flavone derivatives via heteroannulation in moderate to good yields with a similar silver-catalyzed system. The reactions proceed under relatively mild reaction conditions and tolerate a wide variety of functional groups. Control experiments indicated that both the reactions undergo radical processes. (Figure presented.).
Meng, Mengting,Wang, Guofang,Yang, Liangfeng,Cheng, Kai,Qi, Chenze
supporting information
p. 1218 - 1231
(2018/02/16)

Anti-Selective Catalytic Asymmetric Nitroaldol Reaction of α-Keto Esters: Intriguing Solvent Effect, Flow Reaction, and Synthesis of Active Pharmaceutical Ingredients
A rare-earth metal/alkali metal bimetallic catalyst proved particularly effective for enantioselectively coupling nitroalkanes and α-keto esters in an anti-selective manner to afford synthetically versatile, densely functionalized, and optically active α-nitro tertiary alcohols. A chiral diamide ligand captured two distinct metal cations, giving rise to a catalytically competent solid-phase heterobimetallic catalyst by simple mixing via self-assembly. The advantage of the solid-phase asymmetric catalyst was realized by successful application to the enantio- and diastereoselective reaction in a continuous-flow platform. The use of closely related solvents in terms of structures and polarity parameters, THF and its methylated congener 2-Me-THF, had an unexpectedly large solvent effect both on the reaction rate and the stereoselectivity. The nitroaldol products share a privileged unit for active pharmaceutical ingredients, as demonstrated by the streamlined enantioselective synthesis of the marketed antifungal agents efinaconazole and albaconazole.
Karasawa, Tomoya,Oriez, Rapha?l,Kumagai, Naoya,Shibasaki, Masakatsu
supporting information
p. 12290 - 12295
(2018/09/27)

Domino Synthesis of α,β-Unsaturated γ-Lactams by Stereoselective Amination of α-Tertiary Allylic Alcohols
Tertiary allylic alcohols equipped with a carboxyl group can be smoothly aminated under ambient conditions by a conceptually new and stereoselective protocol under palladium catalysis. The in situ formed Z-configured γ-amino acid cyclizes to afford an α,β-unsaturated γ-lactam, releasing water as the only byproduct. This practical catalytic transformation highlights the use of a carboxyl group acting as an activating and stereodirecting functional group to provide a wide series of pharma-relevant building blocks. Various control reactions support the crucial role of the carboxyl group in the substrate to mediate these transformations.
Xie, Jianing,Xue, Sijing,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
supporting information
p. 16727 - 16731
(2018/11/23)

Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis
The alkynylbenziodoxole derivatives are recently developed alkynylation reagents in organic synthesis, which demonstrate excellent radical alkynylation reactivity in photoredox catalysis reactions. Herein we report the synthesis of alkynylbenziodoxole derivatives with difluoro, monofluoro, monomethoxy, and dimethoxy substitution on the benziodoxole moiety, and investigated their radical alkynylation reactivity for the first time. A series of mechanistic experiments were conducted to study the radical acceptor and oxidative quencher reactivity of alkynylbenziodoxoles, in which unsubstituted alkynylbenziodoxoles played balancing roles in both processes, while electron-rich benziodoxole derivatives demonstrate synthetic advantages in some cases.
Pan, Yue,Jia, Kunfang,Chen, Yali,Chen, Yiyun
p. 1215 - 1221
(2018/06/13)

Three-Component Activation/Alkynylation/Cyclocondensation (AACC) Synthesis of Enhanced Emission Solvatochromic 3-Ethynylquinoxalines
2-Substituted 3-ethynylquinoxaline chromophores can be readily synthesized by a consecutive activation–alkynylation–cyclocondensation (AACC) one-pot sequence in a three-component manner. In comparison with the previously published four-component glyoxylation starting from electron-rich π-nucleophiles, the direct activation of (hetero)aryl glyoxylic acids allows the introduction of substituents that cannot be directly accessed by glyoxylation. By introducing N,N-dimethylaniline as a strong donor in the 2-position, the emission solvatochromicity of 3-ethynylquinoxalines can be considerably enhanced to cover the spectral range from blue–green to deep red–orange with a single chromophore in a relatively narrow polarity window. The diversity-oriented nature of the synthetic multicomponent reaction concept enables comprehensive investigations of structure–property relationships by Hammett correlations and Lippert–Mataga analysis, as well as the elucidation of the electronic structure of the emission solvatochromic π-conjugated donor–acceptor systems by DFT and time-dependent DFT calculations with the PBEh1PBE functional for a better reproduction of the dominant charge-transfer character of the longest wavelength absorption band.
Merkt, Franziska K.,H?wedes, Simon P.,Gers-Panther, Charlotte F.,Gruber, Irina,Janiak, Christoph,Müller, Thomas J. J.
p. 8114 - 8125
(2018/04/02)

The Synthesis of Chiral α-Aryl α-Hydroxy Carboxylic Acids via RuPHOX-Ru Catalyzed Asymmetric Hydrogenation
A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX?Ru) catalyzed asymmetric hydrogenation of α-aryl keto acids has been successfully developed, affording the corresponding chiral α-aryl α-hydroxy carboxylic acids in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 5000 S/C) and the resulting products can be transformed to several chiral building blocks, biologically active compounds and chiral drugs. (Figure presented.).
Guo, Huan,Li, Jing,Liu, Delong,Zhang, Wanbin
supporting information
p. 3665 - 3673
(2017/09/11)

A Copper(I)-Catalyzed Addition/Annulation Sequence for the Two-Component Synthesis of γ-Ylidenebutenolides
A highly efficient Cu(I)-catalyzed addition/annulation sequence has been developed for the synthesis of (Z)-ylidenebutenolides employing readily available α-ketoacids and alkynes as substrates. The reactions employ a simple commercially available Cu(I)-catalyst, display good substrate scope, and deliver products with high stereoselectivity. The synthetic utility of the method is demonstrated by the straightforward derivatization of the ylidenebutenolides into a diverse range of heterocycles, and also by the preparation of the natural product bovolide, and analogs thereof.
Seo, Sangwon,Willis, Michael C.
supporting information
p. 4556 - 4559
(2017/09/11)

Copper-catalyzed oxidative decarboxylative coupling of α-keto acids and sulfoximines
A copper-catalyzed oxidative decarboxylative coupling of α-keto acids with NH-sulfoximines has been developed. With CuBr as the catalyst and K2S2O8 as the oxidant, this reaction enables the formation of a C-N bond and gives N-aroylsulfoximine products in moderate to excellent yields. The reaction mechanism is likely to involve the generation of a reactive aroyl radical intermediate.
Pimpasri, Chaleena,Sumunnee, Ladawan,Yotphan, Sirilata
supporting information
p. 4320 - 4327
(2017/07/10)

α-Keto Acids as Acylating Agents in the Synthesis of 2-Substituted Benzothiazoles and Benzoselenazoles
Herein, we report the first decarboxylative oxidation of α-keto acids that is promoted by sodium metabisulfite (Na2S2O5) to obtain 2-substituted benzothiazoles and benzoselenazoles. Diaryl disulfides and diselenides were used as chalcogen sources, and the desired products were obtained in moderate to excellent yields. This protocol does not require an inert gas, transition metals, or harsh reaction conditions, and CO2 is released as an environmentally benign coproduct. The presence of Na2S2O5 was essential to guarantee that the reaction reached completion and afforded maximum product yields.
Lima, David B.,Penteado, Filipe,Vieira, Marcelo M.,Alves, Diego,Perin, Gelson,Santi, Claudio,Lenard?o, Eder J.
supporting information
p. 3830 - 3836
(2017/07/22)

Aldehydes as Carbon Radical Acceptors: Silver Nitrate Catalyzed Cascade Decarboxylation and Oxidative Cyclization toward Dihydroflavonoid Derivatives
Silver nitrate-catalyzed cascade decarboxylation and oxidative cyclization of α-oxocarboxylic acids, alkenes, and aldehydes is demonstrated for the first time. With ammonium persulfate as the oxidant, the cascade reactions afford dihydroflavonoid derivatives as products in moderate to good yields, exhibiting a broad substrate tolerance. Control experiments indicated that the mechanism includes a radical pathway with aldehydes as the carbon radical acceptors. (Figure presented.).
Yang, Wen-Chao,Dai, Peng,Luo, Kai,Ji, Yi-Gang,Wu, Lei
supporting information
p. 2390 - 2395
(2017/07/22)