Functionalization of 2,3,4,5-Tetrahydro-1,5-benzodiazepin-2(1 H)-ones by Electrophilic Aromatic Substitution

Highly substituted, novel, 8- and 9-nitro-2,3,4,5-tetrahydro-1,5-benzodiazepin-2(1H)-ones were obtained by direct nitration of the 7-bromo-5-trifluoroacetyl (or formyl)-substituted tetrahydrobenzodiazepinones. Alkaline and acidic hydrolysis of the novel mononitro derivatives was examined. Semiempirical AM1 calculations of aromatic substituents orientation in the nitration products are presented.     

Theoretical study on the mechanism of thieno[3,2‐b]benzofuran bromination: the importance of Lewis and non‐Lewis type NBOs interactions along the reaction path

A density functional theory study has been performed to estimate the electrophilic thieno[3,2‐b]benzofuran bromination reaction. Optimized structures for all stationary points were examined by employing the B3LYP and BMK at the 6‐31++G(d,p), 6‐311G(d,p), and 6‐311++G(d,p) levels of theory. The solvent polarity has a significant effect on a reduction of activation energies barriers. The reaction involves the formation of a triangle complex, migration of a proton through the bromine moiety followed by ionization of the bromine bond, and activation to the σ‐complex. Finally, the σ‐complex transforms into the reaction products. The natural bond orbital (NBO) population analysis was performed along the reaction minimal energy path defined as a function of the intrinsic reaction coordinate (IRC). The evolution of interaction energies between filled and empty NBOs along IRC has been estimated. The importance of these interactions for the disruption of Br?Br and C?H bonds and creation of C?Br and H?Br bonds have been emphasized. The changes in NBOs hybridization, covalency effects, electrostatic potential density maps, and occupancy of natural bonds have been investigated along IRC. The results obtained explain well the essence of bonding transformations and electron density changes during the reaction. Copyright © 2015 John Wiley & Sons, Ltd.     

Researches on thiazolobenzodiazepines: Behavior of tetrahydro‐1,5‐benzodiazepinethiones with aromatic α‐haloketones

A number of 1‐substituted 4H,5H,6H‐[1,3]thiazolo[3,2‐a][1,5]benzodiazepinium‐11‐bromides and S‐(2‐oxo‐2‐phenyl‐X‐(p)‐ethyl)‐3‐(2‐methyl‐1H‐benzimidazol‐1‐yl) propane (or butane) thioate hydrobromides were obtained by direct reaction of the 5‐acetyl(or formyl, or anilinocarbonyl)‐substituted tetrahydro‐1,5‐benzodiazepine‐2‐thiones with aromatic α‐bromoketones. 2‐[(1‐Acetyl‐2(or 3)‐methyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepin‐4‐yl) sulfanyl]‐1‐phenylethanones as intermediates of the formation of thiazolo [3,2‐a][1,5]benzodiazepine and N‐substituted 2‐methyl‐1H‐benzimidazole derivatives have been synthesized. Semiempirical AM1 calculations of a mechanism and energetic parameters for the heptatomic nucleus rearrangement to benzimidazole ring are presented. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:72–81, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20414     

Visualization of structural changes in cellulosic substrates during enzymatic hydrolysis using multimodal nonlinear microscopy

Enzymatic hydrolysis of cellulose provides a renewable source of monosaccharides for production of variety of biochemicals and biopolymers. Unfortunately, the enzymatic hydrolysis of cellulose is often incomplete, and the reasons are not fully understood. We have monitored enzymatic hydrolysis in terms of molecular density, ordering and autofluorescence of cellulose structures in real time using simultaneous CARS, SHG and MPEF microscopy with the aim of contributing to the understanding and optimization of the enzymatic hydrolysis of cellulose. Three cellulose-rich substrates with different supramolecular structures, pulp fibre, acid-treated pulp fibre and Avicel, were studied at microscopic level. The microscopy studies revealed that before enzymatic hydrolysis Avicel had the greatest carbon-hydrogen density, while pulp fibre and acid-treated fibre had similar density. Monitoring of the substrates during enzymatic hydrolysis revealed the double exponential SHG decay for pulp fibre and acid-treated fibre indicating two phases of the process. Acid-treated fibre was hydrolysed most rapidly and the hydrolysis of pulp fibre was spatially non-uniform leading to fractioning of the particles, while the hydrolysis of Avicel was more than an order of magnitude slower than that of both fibres.     

DFt study of the regioselectivity of addition of sulfenylchloride to ethenes

The electrophilic addition reactions of methylsulfenyl chloride to the double bonds of functionalized ethenes have been studied theoretically. Density functional theory (DFT) calculations have been applied for starting species and ethene‐based sulfonium intermediates bearing substitutes at α‐carbon atom to study geometrical parameters and electronic states of plausible intermediate forms. The quantum chemical optimizations of intermediates indicate that the episulfonium ion is the most likely methyl‐ or carboxyl‐substituted ethane‐based intermediate. However, with phenyl substituents the intermediate is more like a carbonium than an episulfonium ion. The role of sulfur appears to be that of directing the stereochemistry of the addition reaction of chloride, forming the trans product upon nucleophilic attack on the C—C bond of the episulfonium ion. The regioselectivity features of the opening of the episulfonium ion by the chloride anion depend on the LUMO and LUMO+1 of the episulfonium ion and the approaching HOMO of chlorine. The results of the theoretical investigations are in agreement with experiment. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:695–703, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20378     

A straightforward synthesis of novel 4H‐thiazolo[3,2‐d][1,5]benzodiazepine derivatives

The novel 4H‐thiazolo[3,2‐d][1,5]benzodiazepinium salts have been synthesized in a single step by the reaction of the variously substituted 2,3,4,5‐tetrahydro‐1,5‐benzodiazepine‐2(1H)‐thiones and bromoacetaldehyde diethyl acetal. Cyclization is obviously influenced by the nature of the substituents in the benzodiazepine system. Theoretical modeling and B3LYP DFT computational studies are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:363–368, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20026     

Mediated oxidation of ascorbic acid on a homologous series of ferrocene-terminated self-assembled monolayers

The kinetics of electrocatalytic oxidation of ascorbate was studied on a series of redox self-assembled monolayers (SAMs) of the general formula Fc(CH2)4COO(CH2)nSH as electron-transfer mediators, where Fc is the ferrocenyl group and n = 3, 6, 9, and 11. We show that the rate of electron transfer from ascorbate to the surface-confined Fc+ decreases with increasing n. The rationale for the dependence of the rate of electrocatalytic activity and n, in the presence of ClO4, is obtained from Fourier-transform surface-enhanced Raman spectroscopy (FT-SERS), cyclic voltammetry, and electrochemical quartz crystal microbalance (EQCM) data. In particular, FT-SERS shows decreasing amounts of surface-bound ClO4- upon oxidation of the ferrocene with decreasing n, while EQCM data show the effective electrode mass increase was consistently higher on the shorter chain SAMs. This mass increase is likely due to increasing ferricinium cation hydration. As n decreases, the SAMs become less ordered (FT-SERS data), as is widely known from previous literature. Disorder favors water penetration into the SAM, which, in turn, increases the hydration of the Fc+ (EQCM data). Increased hydration of the Fc+ impedes the formation of Fc+-ClO4- ion pairs (EQCM and FT-SERS data), which, consequently, accelerates the electrocatalytic electron transfer from the solution-dissolved ascorbate.