- Hydrogen-Bond Catalysis of Imine Exchange in Dynamic Covalent Systems
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The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
- Schaufelberger, Fredrik,Seigel, Karolina,Ramstr?m, Olof
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- Synthesis and erythroid induction activity of new thiourea derivatives
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Background: The use of medicinal agents to augment the fetal hemoglobin (HbF) accretion is an important approach for the treatment of sickle-cell anemia and β-thalassemia. HbF inducers have the potential to reduce the clinical symptoms and blood transfusion dependence in the patients of β-hemoglobinopathies. Objective: The current study was aimed to examine the erythroid induction potential of newly synthesized thiourea derivatives. Methods: Thiourea derivatives 1-27 were synthesized by using environmentally friendly methods. Compounds 3, 10 and 22 were found to be new. The structures of synthesized derivatives were de-duced by using various spectroscopic techniques. These derivatives were then evaluated for their erythroid induction using the human erythroleukemic K562 cell line, as a model. The benzidine-H2 O2 assay was used to evaluate erythroid induction, while HbF expression was studied through immunocyto-chemistry using the Anti-HbF antibody. Cytotoxicity of compounds 1-27 was also evaluated on mouse fibroblast 3T3 cell line and cancer Hela cell line using MTT assay. Result: All the compounds (1-27) have not been reported for their erythroid induction activity previ-ously. Compounds 1, 2, and 3 were found to be the potent erythroid inducing agents with % induction of 45± 6.9, 44± 5.9, and 41± 6.1, at 1.56, 0.78, and 0.78 μM concentrations, respectively, as compared to untreated control (12 ± 1 % induction). Furthermore, compound 1, 2, and 3 significantly induced fetal hemoglobin the expression up to 4.2-fold, 4.06-fold, and 3.52-fold, respectively, as compared to untreated control. Moreover, the compounds 1-4, 6-9, 11, 12, 15, 17, 19, 22, 23, and 25 were found to be non-cytotoxic against the 3T3 cell line. Conclusion: This study signifies that the compounds reported here may serve as the starting point for the designing and development of new fetal hemoglobin inducers for the treatment of β-hemoglobinopathies.
- Siddiqui, Hina,Shafi, Sarah,Ali, Hamad,Musharraf, Syed Ghulam
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p. 121 - 133
(2021/03/03)
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- Hydroamination of isocyanates and isothiocyanates by alkaline earth metal initiators supported by a bulky iminopyrrolyl ligand
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A series of new heteroleptic alkaline earth (Ae) metal complexes of general formula [{(Ph2CHN-CH)2C4H2N}AeI(THF)3] {Ae = Ca (2), Sr (3), and Ba (4)} were synthesizedviasalt metathesis by reacting potassium salt of ligand1-K[{(Ph2CHN-CH)2C4H2N}K(THF)2] with anhydrous alkaline earth metal diiodides (AeI2). The homoleptic calcium and barium complexes [{(Ph2CHN-CH)2C4H2N}2Ae] [Ae = Ca (5), Ba (6)] were prepared by treating metal bis-hexamethyldisilazide [Ae{N(SiMe3)2}2(THF)2] with the protic ligand1-H[(Ph2CH-N-CH)2C4H2NH] in a 1:2 molar ratio. Calcium complex5was used as an active pre-catalyst for the addition of N-H bond of arylamines across the heterocumulenes such as phenylisocyanate (PhNCO) and phenylisothiocyanate (PhNCS) under neat conditions, and up to 99% yields of the corresponding urea and thiourea derivatives were obtained.
- Bano, Kulsum,Anga, Srinivas,Jain, Archana,Nayek, Hari Pada,Panda, Tarun K.
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supporting information
p. 9419 - 9428
(2020/06/17)
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- 2-Picolylamino(diphenylphosphinoselenoic)amide supported zinc complexes: Efficient catalyst for insertion of N–H bond into carbodiimides, isocyanates, and isothiocyanate
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We report here the hydroamination of heterocumulenes such as carbodiimides, isocyanates, and isothiocyanates by zinc complexes supported by the ligand 2-picolylamino-(diphenylphosphinoselenoic)amide [{(Ph2P-(?Se)}2NCH2(C5H4N)] (1). A series of zinc complexes [κ2-{(Ph2P-(?Se)}2NCH2(C5H4N)ZnX2] [(X?Cl (2), Br (3a), I (4)] were prepared from ligand 1 and the corresponding zinc dihalide in a 1:1 molar ratio at 60°C in a chloroform solvent. The reaction of ligand 1 and ZnBr2 in methanol yielded another zinc complex [κ2-{(Ph2P-(?Se)}2NCH2(C5H4N)ZnBr2(CH3OH)] (3b). The molecular structures of compounds 3a, 3b, and 4 were established through single-crystal X-ray diffraction analyses. The solid-state structures of all the complexes revealed a κ2- chelation through pyridine nitrogen and selenium atoms of ligand 1 to the zinc ion. Complex 2 proved to be a competent pre-catalyst for the addition of the amine N–H bond to carbodiimides, isocyanates, and isothiocyanates. The reaction scope was expanded to reactions of aliphatic and aromatic amines with phenylisocyanate and phenylisothiocyanate in toluene solvents, which proceeded rapidly at room temperature with 5 mol% catalyst loading to yield (up to 99%) the corresponding derivatives of urea and thio-urea. However, a temperature of 90°C was needed for the hydroamination of N,N′ dicyclohexylcarbodiimide. We also report the most plausible mechanism of the hydroamination reaction.
- Harinath, Adimulam,Bano, Kulsum,Ahmed, Shakil,Panda, Tarun K.
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supporting information
p. 23 - 32
(2017/09/25)
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- Hydroamination of carbodiimides, isocyanates, and isothiocyanates by a bis(phosphinoselenoic amide) supported titanium(IV) complex
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The hydroamination of heterocumulenes such as carbodiimides, isocyanates, and isothiocyanates by a bis(phosphinoselenoic amide) supported titanium(iv) complex as a precatalyst is reported here. The titanium(iv) complex [{Ph2P(Se)NCH2CH2NPPh2(Se)}Ti(NMe2)2] (1) was synthesised by the reaction of tetrakis-(dimethylamido)titanium(iv) [Ti(NMe2)4] with [{Ph2P(Se)NHCH2CH2NHPPh2(Se)}] in toluene at ambient temperature. Titanium complex 1 proved to be a competent pre-catalyst for the addition of an amine N-H bond to carbodiimides, isocyanates, and isothiocyanates. The reaction scope was expanded to reactions of aliphatic and aromatic amines with phenylisocyanates and phenylisothiocyanates in toluene solvents proceeding rapidly at room temperature with 5 mol% catalyst loadings to yield the corresponding urea and thio-urea derivatives up to 99%. However, ambient temperature was needed for hydroamination of 1,3-dicyclohexylcarbodiimide. The amine addition reactions with isocyanates showed first order kinetics with respect to catalyst 1 as well as substrates. The most plausible mechanism for the hydroamination reaction was established by isolating 1,1-dimethylphenyl urea as a side product.
- Bhattacharjee, Jayeeta,Das, Suman,Kottalanka, Ravi K.,Panda, Tarun K.
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supporting information
p. 17824 - 17832
(2016/11/18)
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