Synthesis and properties of methyl hydropyrimidineacetates

The alkylation of 1-aryl-substituted dihydro-2,4(1H,3H)-pyrimidinediones with methyl 2-bromoacetate has been studied followed by hydrolysis and condensation of the products with o-phenylenediamine. The compounds have been identified by NMR, and IR spectrometry and mass spectrometry. Structural characteristics in the ¹H and ¹³C NMR spectra of the synthesized are discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 1095–1105, July, 2007.     

The role of fluorine in the stereoselective tandem aza-Michael addition to acrylamide acceptors: an experimental and theoretical mechanistic study

Aza-Michael additions of alpha-amino esters to fluorinated acceptors take place in a highly stereoselective manner, to give partially modified Psi[NHCH2]retropeptides incorporating a hydrolytically stable trifluoroalanine mimic. The reaction mechanism has been investigated experimentally and theoretically, in order to explain the effect of the trifluoromethyl group on the reactivity and the origins of the experimentally observed stereocontrol. The reaction is a two-step process, involving a tandem aza-Michael addition followed by a stereoselective hydrogen transfer. Both steps are base-catalyzed. The high level of stereocontrol is the result of a combination of electrostatic interactions and steric effects.     

Organocatalytic ring expansion of beta-lactams to gamma-lactams through a novel N1-C4 bond cleavage. direct synthesis of enantiopure succinimide derivatives

Tetrabutylammonium cyanide (20 mol %) catalyzes ring expansion of 4-(arylimino)methylazetidin-2-ones 2 to 5-aryliminopyrrolidin-2-ones 3 through a novel N1-C4 bond cleavage of the beta-lactam nucleus. New, efficient one-pot protocols to enantiopure succinimide derivatives 3 and 4 from beta-lactam aldehydes 1 have also been developed. [reaction: see text]     

I2-Catalyzed enantioselective ring expansion of beta-lactams to gamma-lactams through a novel C3-C4 bond cleavage. Direct entry to protected 3,4-dihydroxypyrrolidin-2-one derivatives

Molecular iodine (10 mol%) efficiently catalyzes the ring expansion of 4-oxoazetidine-2-carbaldehydes in the presence of tert-butyldimethyl cyanide to afford protected 5-cyano-3,4-dihydroxypyrrolidin-2-ones with good yield and high diastereoselectivity, through a novel C3-C4 bond cleavage of the beta-lactam nucleus.     

Hydrogen peroxide synthesis: an outlook beyond the anthraquinone process

Hydrogen peroxide (H2O2) is widely used in almost all industrial areas, particularly in the chemical industry and environmental protection. The only degradation product of its use is water, and thus it has played a large role in environmentally friendly methods in the chemical industry. Hydrogen peroxide is produced on an industrial scale by the anthraquinone oxidation (AO) process. However, this process can hardly be considered a green method. It involves the sequential hydrogenation and oxidation of an alkylanthraquinone precursor dissolved in a mixture of organic solvents followed by liquid-liquid extraction to recover H2O2. The AO process is a multistep method that requires significant energy input and generates waste, which has a negative effect on its sustainability and production costs. The transport, storage, and handling of bulk H2O2 involve hazards and escalating expenses. Thus, novel, cleaner methods for the production of H2O2 are being explored. The direct synthesis of H2O2 from O2 and H2 using a variety of catalysts, and the factors influencing the formation and decomposition of H2O2 are examined in detail in this Review.     

Reactions of 9-alkyl-3-aminocarbazoles with ethyl-3-oxo-butanoate and identification of the products obtained

The reactions in benzene of 9-alkyl-3-aminocarbazoles with ethyl-3-oxobutanoate yielded ethyl-3-[(9-alkyl-9H-carbazol-3-yl)amino]but-2-enoate condensation products or N-(9-ethyl-9H-carbazol-3-yl)-3-oxobutanamide acylation products. The condensation products were cyclized to the corresponding 4,7-dihydro-pyrido[2,3-c]-carbazol-1-ones upon heating in mineral oil at 240-250 degrees C. The structures of the synthesized compounds were investigated by IR, mass spectrometry, (1)H- and (13)C-NMR spectroscopy and MM2 molecular mechanics and AM1 semi-empirical quantum mechanical methods.     

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.

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Phthalocyanine-pyrene conjugates: a powerful approach toward carbon nanotube solar cells

In the present work, a new family of pyrene (Py)-substituted phthalocyanines (Pcs), i.e., ZnPc-Py and H(2)Pc-Py, were designed, synthesized, and probed in light of their spectroscopic properties as well as their interactions with single-wall carbon nanotubes (SWNTs). The pyrene units provide the means for non-covalent functionalization of SWNTs via π-π interactions. Such a versatile approach ensures that the electronic properties of SWNTs are not impacted by the chemical modification of the carbon skeleton. The characterization of ZnPc-Py/SWNT and H(2)Pc-Py/SWNT has been performed in suspension and in thin films by means of different spectroscopic and photoelectrochemical techniques. Transient absorption experiments reveal photoinduced electron transfer between the photoactive components. ZnPc-Py/SWNT and H(2)Pc-Py/SWNT have been integrated into photoactive electrodes, revealing stable and reproducible photocurrents with monochromatic internal photoconversion efficiency values for H(2)Pc-Py/SWNT as large as 15 and 23% without and with an applied bias of +0.1 V.     

On the stability of the hydrogen chloride complexes with ethylene and acetylene. A high resolution gas phase and ab initio study

The temperature dependencies of the intensities of the HCl stretching bands of the hydrogen chloride complexes with acetylene and ethylene have been used to obtain estimates of the dissociation enthalpies of the two complexes. Quantum chemical calculations on the Hartree Fock and DFT/B3LYP levels of theory have been combined with experimental data to give estimates of the intensities of the HCl stretching vibration in the two complexes.