- KINETIC STUDY OF THE FORMATION AND RUPTURE OF STABLE TETRAHEDRAL INTERMEDIATES. C-O, C-N and C-S BOND FORMATION
-
Measured pseudo-first-order rate constants for intramolecular formation of tetrahedral intermediates from N-2-hydroxyethylphthalimide, N-2-aminoethylphthalimide and N-2-thioethylphthalimide at pH > 6 are reported.The reaction is specific and general base catalysed, with β(Bronsted) values 0.44, 0.52 and 0.52 respectively.From a plot of log kb (general base rate constants) vs γ' , β'nuc values of 0.01 (with OH- as specific base), 0.25 (with imidazole as general base) and 0.27 (with HPO42- as general base were obtained).The observed relationships pxy = υβ'nuc/ - υpKa = - υβ(Bronsted)/υγ' = 0.03 is supported by the predictions of an energy contour diagram, which, on extrapolation to a non-stable tetrahedral intermediate, predicts a late and slightly protonated transition state for the cleavage process.At pH 0.3 and α 0.1.A fast equilibrium between the intermediate and its N-protonated (amide) form is reached.The general base rupture of the latter is faster than that of the corresponding non-protonated intermediate by a factor of ca 1E9 - 1E10-fold.
- Nunez, Oswaldo,Rodriguez, Jose,Angulo, Larry
-
-
Read Online
- Synthesis, antiproliferative, and antimicrobial properties of novel phthalimide derivatives
-
In this research, a series of new phthalimide derivatives with disulfide bonds were designed and synthesized, and their in vitro antiproliferative activities against normal cell lines L929, human cancer cells Hela, MCF-7, and A549 were assessed via the CCK-8 assay. At the same time, in vitro antimicrobial activities of all compounds were evaluated against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. The preliminary bioassay results showed that a series of derivatives of phthalimide 6a–e, 7a–e, 8a–e, and 9a–e exhibited different degrees of antiproliferative activity, and some compounds revealed higher antiproliferative effects than the positive control 5-fluorouracil. Compound 9b (IC50 = 2.86 μM) exhibited the best proliferation inhibitory activities against A549 cells. It is shown that compounds 6b (IC50 = 2.94 μM) and 6c (IC50 = 3.20 μM) exhibited excellent biological activities against Hela cells. Compound 9b (IC50 = 3.21 μM) displayed the highest antitumor activities against MCF-7 cells. In addition, most of the target compounds had relatively low cytotoxicities against the normal cell line L929. The biological results indicated that all the tested compounds possessed antimicrobial activity with certain degrees against E. coli and S. aureus. [Figure not available: see fulltext.]
- Chi, Chun-Lan,Xu, Lu,Li, Jun-Jie,Liu, Yang,Chen, Bao-Quan
-
p. 120 - 131
(2021/11/30)
-
- Phenyliodine(III) Diacetate/I2-Mediated Domino Approach for Pyrrolo[1,4]Thiazines and 1,4-Thiazines by a One-Pot Morin Rearrangement of N,S-Acetals
-
An efficient domino transformation using a phenyliodine(III) diacetate (PIDA)/I2 combination towards Morin 1,4-thiazine compounds has been developed starting from N,S-acetals. The latter leads to “one-step” regioselective methylene insertion without the need for traditional sulfoxide intermediates in good yields. The reaction involves easily accessible N,S-acetals obtained from cost-effective basic ketones and cysteamine as starting materials. This process ultimately leads to 1,4-thiazines related to natural product and fused derivatives necessary for further QSAR study.
- Danton, Fanny,Othman, Mohamed,Lawson, Ata Martin,Moncol, Ján,Ghinet, Alina,Rigo, Beno?t,Da?ch, Adam
-
supporting information
p. 6113 - 6118
(2019/04/17)
-
- Enantioselective Synthesis of N,S-Acetals by an Oxidative Pummerer-Type Transformation using Phase-Transfer Catalysis
-
Reported is the first enantioselective oxidative Pummerer-type transformation using phase-transfer catalysis to deliver enantioenriched sulfur-bearing heterocycles. This reaction includes the direct oxidation of sulfides to a thionium intermediate, followed by an asymmetric intramolecular nucleophilic addition to form chiral cyclic N,S-acetals with moderate to high enantioselectivites. Deuterium-labelling experiments were performed to identify the stereodiscrimination step of this process. Further analysis of the reaction transition states, by means of multidimensional correlations and DFT calculations, highlight the existence of a set of weak noncovalent interactions between the catalyst and substrate that govern the enantioselectivity of the reaction.
- Biswas, Souvagya,Kubota, Koji,Orlandi, Manuel,Turberg, Mathias,Miles, Dillon H.,Sigman, Matthew S.,Toste, F. Dean
-
supporting information
p. 589 - 593
(2018/02/21)
-
- Multimetallic iridium-tin (Ir-Sn3) catalyst in N-acyliminium ion chemistry: Synthesis of 3-substituted isoindolinones via intra- and intermolecular amidoalkylation reaction
-
The multimetallic iridium-tritin (Ir-Sn3) complex [Cp*Ir(SnCl3)2{SnCl2(H2O) 2}] (1) proved to be a highly effective catalyst towards C-OH bond activation of γ-hydroxylactams, leading to a nucleophilic substitution reaction known as the α-amidoalkylation reaction. Catalyst 1 can be easily synthesized from the reaction of (pentamethylcyclocyclopentadienyl)iridium dichloride dimer {[Cp*IrCl2]2} and tin(II) dichloride (SnCl2). In terms of catalyst loading, reaction conditions and yields of the product formed, 1 is found to be superior compared to classical Lewis acid catalysts. Different carbon (arenes, heteroarenes, allyltrimethylsilane, 1,3-dicarbonyls) and heteroatom (alcohols, thiols, amides and sulfonamides) nucleophiles have been successfully employed in the intramolecular and intermolecular alkylations, as well as in heterocyclization reactions. In the majority of cases good to excellent yields of 3-substituted isoindolinones and 5-substituted pyrrolidin-2-ones have been obtained. Besides, the reactions are also atom economical and salt free. It is proposed that the multimetallic Ir-Sn3 catalyst behaves as a mild and selective Lewis acid to activate the γ-hydroxylactam towards the formation of the N-acyliminium ion; the latter being trapped by potent nucleophiles leading to the desired products.
- Maity, Arnab Kumar,Roy, Sujit
-
p. 2627 - 2642
(2014/09/30)
-
- Photochemistry of Phthaloylcsteine, its methyl ester and C-unprotected S-Alkyl derivatives
-
N-Phthaloyl cysteine derivatives 1a-d were photochemically transformed by elimination, decarboxylation, and via electron transfer cyclization to the products 2,3,4 and 6-8. The spin selectivities of the singlet and triplet pathways were investigated in acetonitrile and acetone . The excited singlets were prone to elimination and γ-H abstraction (e.g. formation of 5) whereas the triplets cyclized to thiazinoisoindoles. This behavior can be correlated with efficiencies of forward and return electron transfer stepsversus homolytic hydrogen abstraction as exemplified for the cysteine substrate.
- Griesbeck, Axel G.,Hirt, Joachim,Kramer, Wolfgang,Dallakian, Paul
-
p. 3169 - 3180
(2007/10/03)
-
- Blue Copper Models. Spectroscopic and Electrochemical Studies of Copper(II) Complexes with New Ligand Systems containing Sulphur and Nitrogen Donor Atoms
-
A series of new polyfunctional ligands derived from the condensation of 1-isopropyl- or 1-phenyl-3-formyl-2(1H)-pyridinethione with aminoalkylthioalkylbenzimidazoles having alkyl chains of various lengths between the donor atoms and the corresponding copper(II) complexes have been synthesized and spectroscopically characterized.The complexes show marked structural variations according to the length of the alkyl chains of the ligands, square planar, square pyramidal, trigonal bipyramidal, and distorted five-co-ordinate, and for one complex a wider range of distorted structures, including four- and five-co-ordinate, is accessible depending on the solvent and physical state.Electrochemistry in non-aqueous solvents indicates that the copper(II) complexes undergo a quasi-reversible one-electron reduction at markedly positive potentials, in the range from +0.23 to 0.35 V vs. saturated calomel electrode.The complete chemical reversibility of the Cu(II)-Cu(I) redox change has been tested by controlled-potential electrolysis.The five-co-ordinate complexes exhibit reduction potentials 0.1 V higher than the square-planar complexes, independently of their actual geometry, square pyramidal, trigonal bipyramidal, or intermediate between these.
- Casella, Luigi,Gullotti, Michele,Pintar, Alessandro,Pinciroli, Piorella,Vigano, Roberto,Zanello, Piero
-
p. 1161 - 1170
(2007/10/02)
-