Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material,during a comparative nuclear forensics exercise

Journal of Radioanalytical and Nuclear Chemistry - This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear...     

Preparation and reductive transformations of vinylogous sulfonamides (beta-sulfonyl enamines), and application to the synthesis of indolizidines

Condensation between the methiodide salts of 1-alkylpyrrolidine-2-thiones and ethyl [(4-methylphenyl)sulfonyl]acetate or 1-[(4-methylphenyl)sulfonyl]propan-2-one afforded several 2-[[(4-methylphenyl)sulfonyl]methylene]pyrrolidines in good yield. These beta-sulfonyl enamines are sufficiently nucleophilic for cyclisation with internal electrophiles to give sulfone-substituted indolizines, potentially useful scaffolds for alkaloid synthesis. The carbon-carbon double bond in vinylogous sulfonamides was reduced stereoselectively either by catalytic hydrogenation or by treatment with sodium borohydride to yield beta-sulfonyl amines. The sulfone group in beta-acyl-beta-sulfonyl enamines could be removed by hydrogenolysis with sodium amalgam in THF-methanol to give enaminones.     

Bicyclic oxygen heterocycles from γ,δ-unsaturated alcohols: synthetic targets inspired by blepharocalyxin D

trans-2,8-Dioxabicyclodecanes were prepared in high yield with the creation of up to three stereocenters in a single pot by the acid-mediated reaction of γ,δ-unsaturated alcohols with aldehydes (see scheme, Bn=benzyl). This versatile reaction enables the stereoselective introduction of substituents at the C3, C4, C7, and C9 positions of the bicyclic framework.     

Azetidin‐2‐one Versus Chroman‐2‐one: Application of 1H‐13C COSY NMR and Mass Spectroscopy in Structure Elucidation–Class of Compounds

Azetidin‐2‐ones, commonly known as β‐lactams, constitute a biologically important class of compound. Treatment of azetidin‐2‐ones with alkali is known to form diverse types of compounds depending on the stability of the ring. In many cases, the ring is retained in the product at the cost of transformation of substituents. Spectroscopy is the most important tool to characterize the organic compounds. However, in some cases the structures of the products are so closely related that simple IR, ¹H NMR, and ¹³C NMR spectra do not lead to unambiguous structure elucidation. This article reports a novel application of ¹H‐¹³C COSY NMR and mass spectroscopy in determining unequivocally an azetidin‐2‐one ring structure instead of a chroman‐2‐one ring structure for the product obtained by treatment of 1‐benzhydryl‐3,3‐bis(4‐methylphenyl)‐4‐[2‐(o‐dip‐tolylacyl)hydroxyphenyl]‐2‐azetidinone with ethanolic sodium hydroxide at room temperature.     

Spectroscopic characterization of the 1-substituted 3,3-diphenyl-4-(2'-hydroxyphenyl)azetidin-2-ones: application of (13)C NMR, (1)H-(13)C COSY NMR and mass spectroscopy

The article deals with spectroscopic characterization of azetidin-2-ones. The presence of substituents like hydroxyl, fluoro, methoxy and benzhydryl, etc., on the azetidin-2-one ring significantly affects the IR absorption and (13)C NMR frequencies of the carbonyl group present in these compounds. The presence of an ester carbonyl group or too many methine protons in the molecule has been observed to limit the scope of IR and (1)H NMR spectroscopy in unambiguous assignment of the structure. The application of (13)C NMR, 2D NMR ((1)H-(13)C COSY) and mass spectroscopy in characterization of complex azetidin-2-ones is discussed. An application of the latter two techniques is described in deciding unequivocally between an azetidin-2-one ring and chroman-2-one ring structure for the product obtained by treatment of the 1-substituted 3,3-diphenyl-4-[2'-(O-diphenylacyl)hydroxyphenyl]-2-azetidinones with ethanolic sodium hydroxide at room temperature.     

Multiple-Interaction Self-Assembly in Coordination Chemistry

This work briefly reviews self-assembly reactions which involve multiple interactionsin coordination chemistry. Two classes of such reactions are recognised: (i) uni-mediatedprocesses in which several different coordinate interactions cooperate or compete with eachother, and (ii) multi-mediated processes in which coordinate interactions are accompaniedby one or more non-coordinate interactions. In both cases the result is often the same: thegeneration of considerable and hierarchical structural complexity in the product.