Quantum-chemical modelling of the reactivity of charcoal surface double bonds

LCAO MO SCF calculations using the 3-21G basis were used to study the electronic and three-dimensional structure of several polycyclic aromatic hydrocarbons as models for the surface of activated charcoal. Localized carbon-carbon double bonds capable of adding electrophilic reagents were found on the periphery of these molecules. The reactivity of the peripheral C=C bonds was evaluated relative to consecutive bromination reactions of the C₅₄H₁₈ molecule. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 1, pp. 30–34, January–February, 2008.     

2-溴-3-(1H-吲哚-3)-N-甲基马来酰亚胺的合成

以琥珀酰亚胺为起始原料,经过溴化、甲基化后再与吲哚溴化镁加成反应合成了2-溴-3-(1H-吲哚-3)-N-甲基马来酰亚胺,总收率44.8%,其结构经1H NMR和IR确证.     

A new method for the synthesis of 5-bromo(aryl)methylene-substituted hydantoins

It has been shown that bromination of 5-aryl-5-benzylidene-3,5-dihydro-4H-2-methylthioimidazol-4-one in methylene chloride at room temperature leads to the addition of bromine at the double bond, but the the reaction of 5-aryl-3,5-dihydro-4H-2-methylthio-5-(2-pyridylmethylene)imidazol-4-one gave complex compound of the starting materials. After boiling both of the compounds obtained in ethanol the corresponding 5-[bromo(aryl)methylene]imidazolidine-2,4-diones were obtained. Dedicated to Academician B. A. Trofimov on his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1406–1408, September, 2008.     

Photochemical Bromination of 2,5-Dimethylbenzoic Acid as Key Step of an Improved Alkyne-Functionalized Blue Box Synthesis**

Cyclobis(paraquat-p-phenylene), also known as “blue box”, is a highly electron-deficient macrocycle, widely used as a molecular receptor for small electron-rich molecules. Inserting a reactive functional group onto the molecular structure of this cyclophane is paramount for its inclusion into complex architectures. To this aim, including an alkyne moiety would be ideal, because it can participate in click reactions. However, the synthesis of such alkyne-functionalized cyclophane suffers from several drawbacks: the use of toxic and expensive CCl₄, the need for high-pressure reactors, and overall low yield. We have revised the existing synthesis of this cyclophane derivative bearing an alkyne moiety, to overcome all these limitations. In particular, photochemical radical bromination is adopted to obtain a sensitive intermediate. We demonstrated that the synthesized host molecule can be functionalized via click reactions and take part in radical-radical interactions. Our work makes a key functionalized paraquat macrocycle more accessible, facilitating the development of novel redox-responsive systems.     

Efficient and convenient synthesis,characterization, and antimicrobial evaluation of some new tetracyclic 1,4-benzothiazines

In the present study, 20 new tetracyclic 1,4-benzothiazines (4a–4 t) were conveniently synthesized in good yields and characterized by different spectral and physical techniques. The in vitro antimicrobial evaluation of the synthesized benzothiazine derivatives was performed by serial dilution against two Gram-positive bacteria [Bacillus subtilis (MTCC 441) and Staphylococcus epidermidis (MTCC 6880)], two Gram-negative bacteria [Escherichia coli (MTCC 1652) and Pseudomonas aeruginosa (MTCC 424)], and two fungal strains [Candida albicans (MTCC 227) and Aspergillus niger (MTCC 8189)]. The derivatives 4 l and 4 t were found to be more potent than standard drug, i.e., fluconazole, against A. niger and C. albicans, respectively.     

Poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) as powerful reagents for benzylic bromination

N,N,N′,N′-Tetrabromobenzene-1,3-disulfonamide [TBBDA], poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS], and novel poly(N,N′-dibromo-N-phenylbenzene-1,3-disulfonamide) [PBPS] can be used for bromination of benzylic positions in solvent.     

Peripheral Hexabromination,Hexaphenylation, and Hexaethynylation of meso‐Aryl‐Substituted Subporphyrins

Effective peripheral fabrication methods of meso‐aryl‐substituted subporphyrins were explored for the first time. Hexabrominated subporphyrins 2 were prepared quantitatively from the bromination of subporphyrins 1 with bromine. Hexaphenylated subporphyrins 3 and hexaethynylated subporphyrins 4 and 5 were synthesized by Suzuki–Miyaura coupling and Stille coupling, respectively, in good yields. X‐ray crystal structures of 2 b , 3 b , 4 b , and 5 a revealed preservation of the bowl‐shaped bent structures with bowl depths similar to that of 1 . Hexaethynylated subporphyrins exhibit large two‐photon‐absorption cross‐sections due to effective delocalization of the conjugated network to the ethynyl substituents.     

Synthesis of dimethyl ether from methane mediated by HBr (Special column of methane transformation, Article)

Dimethyl ether (DME) was synthesized from methane through a two-step process, in which CH₃Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO₂ catalyst and then, in the second step, CH₃Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl₂/SiO₂ catalyst was found to be the most active, but it deactivated because of Cl⁻ losing.