The first ionic liquid-promoted three-component coupling strategy for an expeditious synthesis of β-nitrocarbonitriles/thiocyanates

A novel and convenient three-component coupling reaction of nitromethane, aromatic aldehydes and trimethylsilyl cyanide (TMSCN) or ammonium thiocyanate has been developed for an expeditious synthesis of β-nitrocarbonitriles or β-nitrothiocyanates, respectively, via C-C and C-S bond-forming reactions. The synthetic protocol strategically involves a one-pot sequential Henry reaction and a Michael addition efficiently promoted by the same ionic liquid [bmim]OH. The main advantages of the present approach include the use of inexpensive simple substrates and an ionic liquid as an efficient reaction promoter for the mild synthesis in a one-pot procedure.     

The first one-pot oxidative 1,2-acetoxysulfenylation and 1,2-disulfenylation of Baylis-Hillman alcohols in an ionic liquid

The first example of tandem oxidation and 1,2-acetoxysulfenylation/1,2-disulfenylation of Baylis-Hillman (BH) alcohols to afford 1,2-acetoxysulfides/1,2-dithioethers is reported. The reaction involves oxidation of BH alcohols with IBX in [bmim]Br to give β-ketomethylene compounds in situ followed by CuI-imidazole-catalyzed 1,2-acetoxysulfenylation with an organodisulfide and acetic acid under air to afford vicinal acetoxysulfides in excellent yields with complete regioselectivity. In the absence of the Cu(I) catalyst, 1,2-disulfenylation takes place to give vicinal dithioethers in 81-90% yields.     

IBX/LiBr-promoted one-pot oxidative anti-Markownikov bromohydroxylation/bromoalkoxylation of Baylis-Hillman olefins

The first example of one-pot oxidative anti-Markownikov bromohydroxylation and bromoalkoxylation of Baylis-Hillman (BH) adducts (olefins) is reported. The reaction is performed at rt using LiBr as the bromine source and 2-iodoxybenzoic acid (IBX) as the oxidant. The process involves oxidation of BH adducts with IBX to give β-ketomethylene compounds in situ, which undergo highly regioselective vicinal functionalization with LiBr/H₂O or LiBr/ROH in the same vessel to afford α-bromo-β-hydroxy or α-bromo-β-alkoxy compounds, respectively, in excellent yields. The α-bromo-β-hydroxy compounds are readily transformed into epoxides in aq NaOH.     

The first ionic liquid-promoted one-pot diastereoselective synthesis of 2,5-diamino-/2-amino-5-mercapto-1,3-thiazin-4-ones using masked amino/mercapto acids

The first expeditious synthesis of 2,5-diamino-/2-amino-5-mercapto-1,3-thiazin-4-ones from masked and activated amino/mercapto acids, viz. 2-phenyl-1,3-oxazol-5-one or 2-methyl-2-phenyl-1,3-oxathiolan-5-one, aromatic aldehydes and thioureas using the ionic liquid [Bmim]Br as an environmentally benign reaction promoter is reported. The synthesis is highly diastereoselective and involves tandem Knoevenagel, Michael and ring transformation reactions in a one-pot procedure. The sequential reaction pathway is supported by the isolation of arylidene derivatives and their Michael adducts with thiourea, and quantitative conversion of the latter into the final products under the same reaction conditions.     

Facility placement with sub-aisle design in an existing layout

In this paper, we consider the integration of facility placement in an existing layout and the configuration of one or two connecting sub-aisles. This is relevant, for example, when placing a new machine/department on a shop floor with existing machines/departments and an existing aisle structure. Our work is motivated by the work of Savas et al. [Savas, S., Batta, R., Nagi, R., 2002. Finite-size facility placement in the presence of barriers to rectilinear travel. Operations Research 50 (6), 1018–1031], that considered the optimal planar placement of a finite-size facility in the presence of existing facilities. Our work differs from theirs in that we consider material handling to be restricted to the aisle structure. We do not allow the newly placed facility to overlap with existing facilities or with the aisle structure. Facilities are rectangular and travel is limited to new or existing aisles. We show that there are a finite number of candidate placements for the new facility. Algorithms are developed to find the optimal placement and the corresponding configurations for the sub-aisles. Complexity of the solution method is analyzed. Also, a numerical example is provided to explore the impact of the number of sub-aisles added.     

Characterization of two epimers, 4alpha and 4beta, of a novel podophyllotoxin-4-O-(D)-6-acetylglucopyranoside from Podophyllum hexandrum by LC-ESI-MS-MS

High-performance liquid chromatography (HPLC) with diode array detection interfaced to electrospray ionization (ESI) mass spectrometry (MS) is applied to identify the two epimers of a novel and minor constituent, podophyllotoxin-4-O-(D)-6-acetylglucopyraniside from high-altitude Podophyllum hexandrum for the first time. This is done by matching the structural information from the tandem MS data with the reported lignan markers. The results show that LC-MS-MS is the method of choice for fast detection and detailed chemical analysis of mixtures in the crude extracts of Podophyllum. The method can be employed in the absence of reference standards for the markers and is particularly useful in view of the scarcity of these rare chemical standards.     

Hydrolysis of acyloxy nitroso compounds yields nitroxyl (HNO)

Nitroxyl (HNO/NO(-)), the reduced form of nitric oxide, has gained attention based on its separate chemistry and biology from nitric oxide. The inherent reactivity of HNO requires new and mechanistically unique donors for the detailed study of HNO chemistry and biology. Oxidation of cyclohexanone oxime with lead tetraacetate yields 1-nitrosocyclohexyl acetate, whereas oxidation of oximes in the presence of excess carboxylic acid gives various acyloxy nitroso compounds. These bright blue compounds exist as monomers as indicated by their infrared, proton, and carbon NMR spectra, and X-ray crystallographic analysis reveals the nitroso groups possess a "nitroxyl-like" bent configuration. Hydrolysis of these compounds produces nitrous oxide, the dimerization and dehydration product of HNO, and provides evidence for the intermediacy of HNO. Both thiols and oxidative metal complexes inhibit nitrous oxide formation. Hydrolysis of these compounds in the presence of ferric heme complexes forms ferrous nitrosyl complexes providing further evidence for the intermediacy of HNO. Kinetic analysis shows that the rate of hydrolysis depends on pH and the structure of the acyl group of the acyloxy nitroso compound. These compounds relax pre-constricted rat aortic rings similar to known HNO donors. Together, these results identify acyloxy nitroso compounds as a new class of HNO donors.     

Synthesis of conformationally constrained lysine analogues

The synthesis of two conformationally constrained lysine analogues is reported. The synthesis of the novel analogue 1 based on the 3-aza-bicyclo[3.1.0]hexane system is accomplished from the known tricycle 3 in eight steps. The synthesis of the analogue 2 is accomplished in eight steps from 4-hydroxy proline. Both analogues are synthesized appropriately protected for Fmoc/Boc solid-phase peptide synthesis.     

Correlation of mesogenic properties with intermolecular interaction energy for homologous series of HnCBP

Intermolecular interaction energy between a pair of molecules of homologous series 4, 4′-disubstituted biphenyl of the general formula HO?(CH₂)_n?O?C₆H₄?C₆H₄?CN(n = 3 ? 11) (H_nCBP) has been evaluated under various interacting conditions viz. stacking, in-plane and terminal interaction. Molecular geometry of the studied molecules was fully optimized without any constraint and checked for imaginary frequencies using hybrid density functional B3LYP combined with 6–31 g^** basis set. Electronic structure of the molecules obtained through these calculations has been utilized to calculate electrostatic and polarization energies under Rayleigh-Schrodinger perturbation theory modified with multi-centered multi-pole expansion method. Dispersion and repulsion energies have been evaluated using Kitaigorodskii formula. The identified minimum energy complexes have been further utilized to evaluate interaction energy under super molecular approach by employing M06 and DFT-D methods. A comparative analysis of the results has been reported with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems.