Mechanistic observations in the gewald syntheses of 2-aminothiophenes

The Gewald syntheses were employed to prepare a series of 2-amino-3-carboethoxythiophenes, and the syntheses of two of these, namely, the 3,4-trimethylene ( 1f ) and 3,4-tetramethylene ( 1g ) derivatives, were examined in detail. In two preparations of 1f , octahydro-6a-(4-morpholinyl)-2-thioxocyclopenta[b]pyrrole-3-carboxylic acid ( 7 ) was a co-product. The structure of 7 was ascertained from its 300 MHz ¹H nmr and ¹³C nmr spectra, and by its conversion to 1,4,5,6-tetrahydro-2-mercaptocyclopenta[b]pyrrole-3-carboxylic acid ethyl ester ( 8 ). Isolation of 7 and other observations led to postulated mechanisms for three of the Gewald thiophene syntheses.     

Molecular Nanocapsules Based on Amphiphilic Hyperbranched Polyglycerols

Polar dyes can be solubilized in apolar media-molecular nanocapsules with hydrophilic interiors have been prepared (see schematic representation) using polyglycerols with narrow polydispersity and simple esterification with fatty acids. These unimolecular micelles offer attractive potential for a variety of applications ranging from controlled drug release to the design of microreactors and catalysts.     

The planar algebra associated to a Kac algebra

We obtain (two equivalent) presentations — in terms of generators and relations — of the planar algebra associated with the subfactor corresponding to (an outer action on a factor by) a finite-dimensional Kac algebra. One of the relations shows that the antipode of the Kac algebra agrees with the ‘rotation on 2-boxes’.     

Actions of Finite Hypergroups

This paper is concerned with actions of finite hypergroups on sets. After introducing the definitions in the first section, we use the notion of maximal actions to characterise those hypergroups which arise from association schemes, introduce the natural sub-class of *-actions of a hypergroup and introduce a geometric condition for the existence of *-actions of a Hermitian hypergroup. Following an insightful suggestion of Eiichi Bannai we obtain an example of the surprising phenomenon of a 3-element hypergroup with infinitely many pairwise inequivalent irreducible *-actions.     

Two characterization theorems for integral operators

Let (X,) be a separable -finite measure space. A bounded operator A on L²(X) is called an integral operator if it is induced by an equation: Af(x) = k(x,y)f(y)d(y), where k is a measurable function on X × X such that |k(x,y)f(y)|d(y) < a.e. for every f in L²(X).In this paper, some results on Carleman operators, due to von Neumann, Tarjonski and Weidmann, are extended to the case of the general integral operator.     

Nitrosyl,nitryl and dioxygenyl hexafluoroplatinate(IV) and (V) and related compounds: Synthesis,reactions and raman spectra

The reactions of PtF₅, O₂PtF₆, PtF₆, IrF₆, NOPtF₆, NO₂PtF₆, NOIrF₆ and NO₂IrF₆ with NOF and NO₂F have been examined under a variety of conditions. The relative ease of synthesis of NOPtF₆, (NO)₂PtF₆, NOIrF₆ and NO₂IrF₆ and the conversion of NOIrF₆ to NOPtF₆ with PtF₆ confirms the order of strong oxidizing properties of Pt^VIF₆, Ir^VIF₆, Pt^VF^-₆ and Ir^VF^-₆. The NO⁺₂ ion is intrinsically unstable with respect to the elimination of oxygen in Pt (IV) and Ir (IV) fluorometallate salts and accordingly there is serious doubt about earlier claims for the synthesis of the (NO⁺)(NO⁺₂)PtF₆ salt. No evidence for the (NO₂)₂PtF₆ could be found.Raman spectral data for NOBF₄, NO₂BF₄, NO₂AsF₆, NOPtF₆, NO₂PtF₆, (NO)₂PtF₆, NOIrF₆, NO₂IrF₆ and (NO)₂IrF₆ are presented and analyzed. The NO⁺₂ ion appears to be linear in all of the compounds and the absence of the Raman forbidden ν₂ fundamental indicates little if any anion-cation interaction at least of the type that leads to a permanent distortion of the cation. In the spectra of all of the nitryl salts, including NO₂BF₄, a low frequency band at about 140 cm^-1 is clearly observed, the intensity and shape of which is a function of the anion. The band probably reflects an unknown lattice dynamic process. No such bands are evident in the spectra of NO⁺ and (NO⁺)₂ salts.     

Hyperbranched Polyether Polyols with Liquid Crystalline Properties

The attachment of mesogens as end groups to hyperbranched polyglycerol (degree of polymerization 22–45; see schematic representation, the rigid mesogens are shown as rods and the flexible alkyl chains as lines) leads to liquid crystalline polymers with narrow polydispersity, whose liquid crystalline behavior is induced by the mesogenic end groups only.     

1,3‐Propane­di­ammonium tetra­thio­tungstate and N,N,N′,N′‐tetra­methyl­ethyl­enedi­ammonium tetra­thio­tungstate

The title complexes, (C₃H₁₂N₂)[WS₄] and (C₆H₁₈N₂)[WS₄], contain tetrahedral [WS₄]²⁻ dianions, which accept a complex series of hydrogen bonds from the organic dications. The strength and number of these hydrogen bonds affect the W—S distances.