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1. Conversion of esters to thioesters under mild conditions

   https://doi.org/10.1039/D1OB00187F  

   Shi, Yijun; Liu, Xuejing; Cao, Han; Bie, Fusheng; Han, Ying; Yan, Peng; Szostak, Roman; Szostak, Michal; Liu, Chengwei (April 2021, Organic & Biomolecular Chemistry)

   null (Ed.)

   We report conversion of esters to thioesters via selective C–O bond cleavage/weak C–S bond formation under transition-metal-free conditions. The method is notable for a general and practical transition-metal-free system, broad substrate scope and excellent functional group tolerance. The strategy was successfully deployed in late-stage thioesterification, site-selective cross-coupling/thioesterification/decarbonylation and easy-to-handle gram scale thioesterification. Selectivity and computational studies were performed to gain insight into the formation of weak C–S bonds by C–O bond cleavage, which contrasts with the traditional trend of nucleophilic additions to carboxylic acid derivatives. 

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2. Decarbonylative sulfide synthesis from carboxylic acids and thioesters via cross-over C–S activation and acyl capture

   https://doi.org/10.1039/D1QO00824B  

   Liu, Chengwei; Szostak, Michal (August 2021, Organic Chemistry Frontiers)

   A method for the synthesis of sulfides from carboxylic acids via thioester C–S activation and acyl capture has been developed, wherein thioesters serve as dual electrophilic activators of carboxylic acids and S-nucleophiles through the merger of decarbonylative palladium catalysis and sulfur coupling. This new concept employs readily available carboxylic acids as coupling partners to directly intercept sulfur reagents via redox-neutral thioester-enabled cross-over thioetherification. The scope of this platform is demonstrated in the highly selective decarbonylative thioetherification of a variety of carboxylic acids and thioesters, including late-stage derivatization of pharmaceuticals and natural products. This method operates under mild, external base-free, and operationally practical conditions, providing a powerful new framework to unlock aryl electrophiles from carboxylic acids and increase the reactivity by employing common building blocks in organic synthesis. 

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3. Palladium-catalyzed decarbonylative Suzuki–Miyaura cross-coupling of amides by carbon–nitrogen bond activation

   https://doi.org/10.1039/c9sc03169c  

   Zhou, Tongliang; Ji, Chong-Lei; Hong, Xin; Szostak, Michal (October 2019, Chemical Science)

   Palladium-catalyzed Suzuki–Miyaura cross-coupling or aryl halides is widely employed in the synthesis of many important molecules in synthetic chemistry, including pharmaceuticals, polymers and functional materials. Herein, we disclose the first palladium-catalyzed decarbonylative Suzuki–Miyaura cross-coupling of amides for the synthesis of biaryls through the selective activation of the N–C(O) bond of amides. This new method relies on the precise sequence engineering of the catalytic cycle, wherein decarbonylation occurs prior to the transmetallation step. The reaction is compatible with a wide range of boronic acids and amides, providing valuable biaryls in high yields (>60 examples). DFT studies support a mechanism involving oxidative addition, decarbonylation and transmetallation and provide insight into high N–C(O) bond activation selectivity. Most crucially, the reaction establishes the use of palladium catalysis in the biaryl Suzuki–Miyaura cross-coupling of the amide bond and should enable the design of a wide variety of cross-coupling methods in which palladium rivals the traditional biaryl synthesis from aryl halides and pseudohalides. 

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4. Decarbonylative ether dissection by iridium pincer complexes

   https://doi.org/10.1039/d0sc03736b  

   Yoo, Changho; Dodge, Henry M.; Farquhar, Alexandra H.; Gardner, Kristen E.; Miller, Alexander J. (November 2020, Chemical Science)

   A unique chain-rupturing transformation that converts an ether functionality into two hydrocarbyl units and carbon monoxide is reported, mediated by iridium( i ) complexes supported by aminophenylphosphinite (NCOP) pincer ligands. The decarbonylation, which involves the cleavage of one C–C bond, one C–O bond, and two C–H bonds, along with formation of two new C–H bonds, was serendipitously discovered upon dehydrochlorination of an iridium( iii ) complex containing an aza-18-crown-6 ether macrocycle. Intramolecular cleavage of macrocyclic and acyclic ethers was also found in analogous complexes featuring aza-15-crown-5 ether or bis(2-methoxyethyl)amino groups. Intermolecular decarbonylation of cyclic and linear ethers was observed when diethylaminophenylphosphinite iridium( i ) dinitrogen or norbornene complexes were employed. Mechanistic studies reveal the nature of key intermediates along a pathway involving initial iridium( i )-mediated double C–H bond activation. 

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5. Crystal structure of N , N -diisopropyl-4-methylbenzenesulfonamide

   https://doi.org/10.1107/S2056989020007185  

   Stenfors, Brock A.; Staples, Richard J.; Biros, Shannon M.; Ngassa, Felix N. (July 2020, Acta Crystallographica Section E Crystallographic Communications)

   The synthesis of the title compound, C 13 H 21 NO 2 S, is reported here along with its crystal structure. This compound crystallizes with two molecules in the asymmetric unit. The sulfonamide functional group of this structure features S=O bond lengths ranging from 1.433 (3) to 1.439 (3) Å, S—C bond lengths of 1.777 (3) and 1.773 (4) Å, and S—N bond lengths of 1.622 (3) and 1.624 (3) Å. When viewing the molecules down the S—N bond, the isopropyl groups are gauche to the aromatic ring. On each molecule, two methyl hydrogen atoms of one isopropyl group are engaged in intramolecular C—H...O hydrogen bonds with a nearby sulfonamide oxygen atom. Intermolecular C—H...O hydrogen bonds and C—H...π interactions link molecules of the title compound in the solid state. 

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