2,3-Dihydro-1H-1,5-benzodiazepines: A conversion of thiolactams to amidines

Summary The synthesis of a new series of diversely N-4 substituted amidines of 2,3-dihydro-1H-1,5-benzodiazepine has been accomplished starting from tetrahydro-1,5-benzodiazepin-2-one derivatives. These compounds were transformed into the desired thiolactams2a–i which reacted in the presence of mercuric chloride with ammonia, as well as primary or secondary amines to give amidines3a–i. Hydrazidines3j–l were prepared by treatment of thiolactams with an excess of hydrazine.

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2,3-Dihydro-1H-1,5-benzodiazepine: Umwandlung von Thiolactamen in Amidine

Zusammenfassung Einige neue N-substituierte Amidine von 2,3-Dihydro-1H-1,5-benzodiazepinen wurden ausgehend von Tetrahydro-1H-1,5-benzodiazepin-2-onen synthetisiert. Letztere wurden in die Thiolactame2a–i umgewandelt und anschließend durch Behandeln mit Ammoniak, primären oder sekundären Aminen in Gegenwart von Quecksilber(II)-chlorid zu den entsprechenden Amidinen3a–i umgesetzt. Die Hydrazinoamidine3j–l wurden aus den Thiolactamen mit Hydrazineüberschuß erhalten.

     

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.     

Synthesis of novel 5‐chlorinated 2‐aminothiophenes using 2,5‐dimethylpyrrole as an amine protecting group

A new synthetic methodology towards substituted 2‐amino‐5‐chlorothiophenes is described. Compounds of this type are important as building blocks for oligomers used in polymer research. Easily available 2‐aminothiophenes underwent Paal‐Knorr reaction to protect the free amino group before electrophilic substitution. Although the chlorination was predicted to proceed at the thiophene ring, only free positions of 2,5‐dimethylpyrrole were substituted. To direct chlorination to the thiophene ring acetamido derivative was prepared first and then chlorinated. Transamination with hexane‐2,5‐dione created a 2,5‐dimethyl pyrrole ring from the acetamido group. In the final step, after treatment with hydroxylamine dihydrochloride, the pyrrole ring is removed and a free amino group is regenerated.     

Surface structure of metal-organic framework grown on self-assembled monolayers revealed by high-resolution atomic force microscopy

The surface structure of an individual metal-organic framework (MOF) microcrystal grown on a functionalized surface has been successfully investigated for the first time in air and vacuum using high-resolution atomic force microscopy. Moreover, this detailed surface analysis has been utilized to optimize the MOF formation procedure to obtain a defect-free surface structure. Comparison of obtained data with recent microscopic studies performed on the same MOF crystal but grown by a conventional procedure clearly shows a much higher quality of crystals produced by surface oriented growth. Importantly, this method of preparing crystals suitable for microscopic analysis is also much faster (3 days compared to 2 years) and, in contrast to the conventional method, produces material suitable for in situ study. These results thus demonstrate for the first time the possibility of nanoscale investigation/modification of MOF surface structure.     

Synthesis of DNA strands site-specifically damaged by c8-arylamine purine adducts and effects on various DNA polymerases

C8-Arylamine-dG and C8-arylamine-dA adducts have been prepared using palladium cross-coupling chemistry. These adducts were subsequently converted into the corresponding 5'-O-DMTr-C8-arylamine-3'-O-phosphoramidites and then used for the automated synthesis of different site-specifically modified oligonucleotides. These "damaged" oligonucleotides have been characterized by ESI-MS, UV thermal stability assays, and circular dichroism, and they have been used in EcoRI assays as well as in primer extension studies using various DNA polymerases.     

Synthesis of α‐aminophosphonates from α‐hydroxyphosphonates; a theoretical study

Two types of reactions, namely the Pudovik reaction of benzaldehyde and acetophenone with diethyl phosphite as well as the substitution of the α‐hydroxyphosphonates so‐formed by primary amines to afford α‐aminophosphonates, were evaluated by quantum chemical calculations at the B3LYP/6‐31G(d,p) level. An unexpected neighboring group effect was found to enhance the substitution. A series of new α‐aminophosphonates was synthesized by the microwave‐assisted substitution of α‐hydroxyphosphonates by alkylamines.     

On the reaction of 3-nitro-1,2-phenylenediamine with ethyl acetoacetate. Condensed dihydrodiazepinones

Condensation of 3-nitro-1,2-phenylenediamine with ethyl acetoacetate in boiling xylene gave two isomeric 2,3-dihydro-4-methyl-9-nitro- and 2,5-dihydro-4-methyl-6-nitro-1H-1,5-benzodiazepin-2-ones, the 9-nitro derivative thermal rearrangement product N-isopropenyl-4-nitrobenzimidazolone and a non cyclic acetoacetamide derivative. At room temperature these reactants afforded 2,3-dihydro-2-ethoxycarbonyl-methyl-2-methyl-4-nitrobenzimidazole.     

Preparation of Polymer‐Metal Composites via In Situ Decomposition of Metal Salts by Frontal Polymerization

Composites containing powdered zinc, and zinc/lead acetate were prepared via frontal polymerization. In the case of the acetates, elemental metal was formed in an in situ decomposition process. The local area function was used to demonstrate the distribution of fillers, and the uniformity of the area fraction for the quantitative characterization of the distribution. With the use of metal acetates, composites of uniform metal distribution can be produced, unlike in systems with metal powder, where the metal particles are enriched at the margin of the sample. It can be established that the specific direct‐current resistance significantly decreases in AA‐TGDMA composites by the addition of zinc acetate, compared to that of the initial monomer mixture. On heating, the unreacted zinc acetate decomposes further, which results in the further decrease in electrical resistance.