Contributors: Grolleau, Jérémie, Frère, Pierre, Gohier, Frédéric
... Abstract Iodination of thiophene derivatives is realized using a simple, fast, and efficient methodology. Iodination of thiophene and 2- or 3-substituted or 3,4-disubstituted thiophenes with N-iodosuccinimide (NIS) activated with 4-toluenesulfonic acid in ethanol gives pure iodinated products that require no further purification.
Highly Regioselective Arylation of 1,2,3-Triazole N-Oxides with Sodium Arenesulfinates via Palladium-Catalyzed Desulfitative Cross-Coupling Reaction
Contributors: Zhu, Jiayi, Chen, Yu, Lin, Feng, Wang, Baoshuang, Huang, Qing, Liu, Liangxian
... Abstract A convenient and highly regioselective palladium-catalyzed direct C5-arylation of 1,2,3-triazole N-oxides was developed in the presence of silver carbonate and tripotassium phosphate. This protocol allowed use of sodium arylsulfinates, diphenylphosphine oxide, and triphenylphosphine as arylating reagents to produce 2-aryl-5-aryl-1,2,3-triazole N-oxides in good to excellent yields, providing a complement to the existing methods for the direct arylation of 1,2,3-triazole N-oxides.
En Route to Novel Furanoside Mimics through Stereoselective Zinc-Mediated Propargylation of N-Benzyl Glycofuranosylamines Using Ultrasound Activation
Contributors: Nicolas, Cyril, Engo-Ilanga, Francis, Cocaud, Chloé, Martin, Olivier
... Abstract Preliminary results on a novel zinc-mediated, ultrasound-promoted chain extension of glycofuranosylamines with a propargyl group are reported. The procedure was applied to d-arabino and d-xylo substrates to give, via Cram-chelate transition states, 1-C-1-(3-trimethylsilyl-2-propynyl)-1-benzylamino pentionols in moderate to good yields and acceptable stereoselectivities (syn/anti ≥4:1). To apply the reaction to the synthesis of galactofuranoside mimics, the d-xylo intermediate was cyclized to afford a 1-C-1-(2-propynyl)-1,4-dideoxy-1,4-imino-l-arabinitol derivative in excellent yield. This building block was used in three examples of CuAAC click reactions with azide compounds to provide the corresponding galactofuranoside mimics.
Nickel-Catalyzed sp3 C–H Bond Activation from Decarboxylative CrossCoupling of α,β-Unsaturated Carboxylic Acids with Amides
Contributors: Zhang, Jia-Xiang, Wang, Yan-Jing, Wang, Nai-Xing, Zhang, Wei, Bai, Cui-Bing, Li, Yi-He, Wen, Jia-Long
... Abstract Nickel-catalyzed functionalization of C(sp3)–H bonds adjacent to a nitrogen atom in amides through decarboxylative cross-coupling of α,β-unsaturated carboxylic acids is reported. A possible reaction mechanism is proposed that involves radical intermediate species.
Regioselectivity of Intramolecular Rhodium-Catalyzed C–H Insertion Reactions of α-Aryl-α-diazocarboxylates: Influence of the Aryl Substituent
Contributors: Wamser, Maximilian, Bach, Thorsten
... Abstract It was found that α-aryl-α-diazocarboxylates react with variable regioselectivity in intramolecular rhodium-catalyzed C–H insertion reactions. 3-(Trialkoxysilyl)propyl esters underwent a clean cis-γ-lactone formation (62–69%) if the aryl rest was a phenyl group while the analogous α-(2-bromophenyl)-α-diazocarboxylates produced the respective β-lactones. In general β-lactone formation was shown to be the only detectable C–H insertion pathway for the latter substrate class irrespective of the ester substituent. The β-lactone products (eight examples) were obtained in yields of 41–68% with a diastereomeric ratio (dr) of 75:25 to 96:4 in favor of the trans diastereoisomer. The 2-bromo substituent could be displaced by an aryl group in a subsequent Suzuki cross-coupling reaction.
Synthesis of 1-Aminoisoquinolines via the Coinage Metal Cocatalyzed Reaction of 2-Alkynylbenzaldoximes with Isocyanoacetates
Contributors: Wang, Tao, Li, Rou, Yu, Danhong, Gu, Chenghao, Xiong, Fei, Chen, Zhiyuan
... Abstract An efficient reaction of 2-alkynylbenzaldoximes with 2-isocyanoacetates cocatalyzed by silver triflate and gold(I) chloride is described, providing 1-aminoisoquinolines in good to excellent yields under mild conditions. Mechanistic experiments suggest that the gold(I) cation might play a crucial role in the activation of the isocyanide substrate. The observed reactivity and the unique pathway of substrate activation in the cocatalyzed processes are quite informative for further study.
Thio-Michael–Aldol–Cyclization Cascade of N-Enoyl Thiazolidinethiones with Aliphatic Aldehydes and Cyclic Ketones
Contributors: Rivas, Veronica, Munive, Laura, Olivo, Horacio
... Abstract A thio-Michael–aldol–cyclization cascade reaction of N-enoyl thiazolidinethiones with aliphatic aldehydes and cyclic ketones was promoted by Ti(IV) chloride to deliver highly complex tricyclic adducts possessing a carbon atom tetrasubstituted with heteroatoms and up to four stereogenic centers in good to very good yields.
A Convenient and Efficient Synthesis of 2-(Het)arylthieno[3,2-b]pyridin-7(4H)-ones and 2,3-Di(het)arylthieno[3,2-b]pyridin-7(4H)-ones
Contributors: Puvvala, Srinu, Jadhav, Vinod, Farooq, Sheikh, Reddy, C., Machiraju, Pavan
... Abstract A simple and efficient synthesis of 2-aryl-3-hydroxythieno[3,2-b]pyridin-7(4H)-ones, 7-methoxy-2,3-diarylthieno[3,2-b]pyridines, and 2,3-diarylthieno[3,2-b]pyridin-7(4H)-ones is presented. The synthesis involves thioalkylation of methyl 4-methoxypicolinate at the 3-position, followed by cyclization in situ to give 2-aryl-7-methoxythieno[3,2-b]pyridin-3-ols. Demethylation of these compounds gives the corresponding 2-arylthieno[3,2-b]pyridin-7(4H)-ones. Further functionalization of 7-methoxy-2-arylthieno[3,2-b]pyridin-3-ols was achieved by converting the hydroxy group into the corresponding triflate, which underwent palladium-catalyzed cross-coupling to give 7-methoxy-2,3-di(het)arylthieno[3,2-b]pyridines. Subsequent demethylation of the 7-methoxy group gave the corresponding pyridinones.
Synthetic and Mechanistic Aspects on the Competition between C–H Insertion and Hydride Transfer in Copper-Mediated Transformations of α-Diazo-β-Keto Sulfones
Contributors: Slattery, Catherine, Ford, Alan, Eccles, Kevin, Lawrence, Simon, Maguire, Anita
... Abstract Competition between C–H insertion and hydride transfer is reported for the copper-catalysed reactions of a range of phenyl-substituted α-diazo-β-keto sulfones. Control of chemoselectivity is possible by alteration of the electronic properties of the diazo substrate. The production of enantioenriched cyclopentanones (up to 89% ee), formed via C–H insertion, and alkylidene tetrahydrofurans (up to 43% ee), produced via hydride transfer, is described. The isolation of products derived from hydride transfer provides mechanistic insight into the copper-mediated C–H insertion of α-diazocarbonyl compounds.
Contributors: Li, Nan, Chen, Dian-Feng, Wang, Pu-Sheng, Han, Zhi-Yong, Gong, Liu-Zhu
... Abstract The hybrid gold(I)/Brønsted acid binary catalyst system enables enynes to participate in an asymmetric relay catalytic cascade intramolecular hydrosiloxylation and asymmetric hetero-Diels–Alder reaction with fluorenyl glyoxylate.