10.1021/acs.joc.7b00512
The study titled "DBU-mediated Diastereoselective Aldol-type Cyanomethylation of Isatins" explores an efficient, metal-free approach to synthesizing 3-substituted 3-hydroxy oxindoles through DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) mediated addition of aryl acetonitrile to N-protected isatin under mild conditions. The researchers optimized the reaction conditions using various N-protected isatins and benzyl cyanides as substrates, achieving good yields and excellent diastereoselectivity. The study also includes DFT calculations to provide mechanistic insights into the aldol-type cyanomethylation process. The cyanomethylated adducts can be further transformed into advanced intermediates of natural product analogues, demonstrating the synthetic utility of this method.
10.1246/cl.1982.1123
The research focuses on the novel synthesis of 4-azoloyl-2-aminoquinolines, which are heterocyclic compounds with potential biological and medicinal activities. The purpose of the study is to explore the synthetic potential, scope, and limitations of activated nitriles in heterocyclic synthesis. The researchers reported a new method for synthesizing these compounds by reacting 3-cyanomethylene derivatives of isatin (Ia, Ib) with 2-pyrazolin-5-one derivatives (IIa, IIb) and 2-ethoxycarbonylmethyl-2-thiazolin-4-one (X). The process involves equimolar amounts of the reactants being refluxed in ethanol with a catalyst, triethylamine, to yield products with molecular formulas corresponding to the addition of IIa,b to Ia. The study concluded that the synthesized compounds possess latent functional substituents, making them promising for further chemical transformations and of interest for biological studies. The research also noted that this is the first reported conversion of indoles into quinolines via a similar route, expanding the understanding of heterocyclic synthesis.
10.1002/ardp.19913240605
The study investigates the reaction between isatin and thiocarbohydrazide, aiming to clarify the structure of the resulting compound. Isatin, a versatile intermediate in heterocyclic chemistry, and thiocarbohydrazide, a thiosemicarbazide derivative, are the primary chemicals involved. The authors challenge the previously reported structure of the reaction product as a spiro system (2-oxo-1',2',4',5'-tetrahydro-spiro[3H-indole-3,3'-1,2,4,5-tetrazine]-6'-thione) and propose that the actual product is a thiocarbohydrazone. They support their claim through various experiments, including condensation reactions with benzaldehyde and α-keto acids, which yield different derivatives. The study also examines the biological activity of these compounds against various strains of bacteria, yeast, and fungi, revealing varying levels of sensitivity. The findings highlight the importance of additional spectral and chemical evidence in determining the structure of complex organic compounds and underscore the potential biological applications of these derivatives.
10.1016/S0040-4039(00)82160-7
The study focuses on the synthesis of isotopically labeled pyrroloquinoline quinone (PQQ), a cofactor found in various microbial dehydrogenases, oxidases, and mammalian copper-containing amine oxidases. The researchers adopted and modified existing chemical synthesis schemes to prepare different isotopically labeled PQQ derivatives, such as 3-13C-PQQ, 3-2H-PQQ, and 8-2H-PQQ. The synthesis of 3-13C-PQQ and 3-2H-PQQ involved the Japp-Klingemann hydrazone synthesis, Fischer indolixation, and Doebner-Von Miller type condensation, using starting materials like methoxy-nitro-aniline and methyl-acetoacetate. For 8-2H-PQQ, a Pfitzinger quinoline synthesis was employed, starting from aminoindole and using reagents like isatin, pyruvic acid, and ceric ammonium nitrate. These isotopically labeled PQQ compounds are valuable for studying the biosynthesis, enzymatic redox catalysis, and physiological role of PQQ in different organisms.
10.1080/00397910903318591
Indirubin derivatives are known for their high activity against various experimental solid tumors and their ability to inhibit cyclin-dependent kinases (CDKs) and glycogen synthase kinases-3 (GSK-3), which play important roles in diseases like cancers. The study explores a simple and convenient route involving oxidation and subsequent condensation of indoxyl and isatin. Acidic reaction conditions are crucial for the condensation of 4-substituted derivatives due to steric hindrance, while both acidic and basic conditions work well for 6-substituted derivatives. The authors successfully synthesized a range of 4- and 6-substituted indirubin derivatives and confirmed their structures using various spectroscopic techniques. The findings provide a novel approach to synthesizing these potentially therapeutic compounds, which could have significant implications for cancer treatment and other related diseases.
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