26767-16-8Relevant articles and documents
α-Oxocarboxylic Acids as Three-Carbon Insertion Units for Palladium-Catalyzed Decarboxylative Cascade Synthesis of Diverse Fused Heteropolycycles
Zhou, Liwei,Qiao, Shujia,Zhou, Fengru,Xuchen, Xinyu,Deng, Guobo,Yang, Yuan,Liang, Yun
, p. 2878 - 2883 (2021/05/05)
A novel palladium-catalyzed decarboxylative cascade cyclization for the assembly of diverse fused heteropolycycles by employing α-oxocarboxylic acids as three-carbon insertion units is reported. This protocol enables the synthesis of isoquinolinedione- and indolo[2,1-a]isoquinolinone-fused benzocycloheptanones in moderate to good yields by the use of different aryl iodides, including alkene-tethered 2-iodobenzamides and 2-(2-iodophenyl)-1H-indoles. Notably, the approach achieves simultaneous construction of both six- and seven-membered rings via sequential intramolecular carbopalladation, C-H activation, and decarboxylation.
Possible competitive modes of decarboxylation in the annulation reactions ofortho-substituted anilines and arylglyoxylates
Laha, Joydev K.,Panday, Surabhi,Tomar, Monika,Patel, Ketul V.
supporting information, p. 845 - 853 (2021/02/09)
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.
Hypervalent Iodine(III)-Promoted Radical Oxidative C-H Annulation of Arylamines with α-Keto Acids
Long, Lipeng,Wang, Jieyan,Gu, Liuqing,Yang, Shiguang,Qiao, Liang,Luo, Guotian,Chen, Zhengwang
supporting information, p. 12084 - 12092 (2021/08/24)
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.
