A Hydrogen Chloride‐Free Pinner Reaction Promoted by Lewis Acids

A hydrogen chloride‐free variation of the Pinner reaction was developed, in which alcohols react with carbonitriles to furnish carboxylates. Best results were achieved with aliphatic alcohols, and aliphatic or benzylic nitriles in the presence of 2 equiv. of trimethylsilyl triflate (Me₃SiOTf). With these substrates, yields exceeding 80% were achieved. A strictly neutral variation of this protocol is possible, when 1 equiv. of Et₃N is added to the reaction mixture.     

On the growth of torsion in the cohomology of arithmetic groups

In this paper we consider certain families of arithmetic subgroups of $\mathrm{SO }^0(p,q)$ and $\mathrm{SL }_3(\mathbb {R})$ , respectively. We study the cohomology of such arithmetic groups with coefficients in arithmetically defined modules. We show that for natural sequences of such modules the torsion in the cohomology grows exponentially.     

Analytic torsion versus Reidemeister torsion on hyperbolic 3-manifolds with cusps

For a non-compact hyperbolic 3-manifold with cusps we prove an explicit formula that relates the regularized analytic torsion associated to the even symmetric powers of the standard representation of \(\mathrm{SL }_2(\mathbb {C})\) to the corresponding Reidemeister torsion. While the analytic torsion is a spectral invariant of the manifold, the Reidemeister torsion is of combinatorial nature. Our proof rests on an expression of the analytic torsion in terms of special values of Ruelle zeta functions as well as on recent work of Pere Menal-Ferrer and Joan Porti.     

Exponential growth of homological torsion for towers of congruence subgroups of Bianchi groups

In this paper we prove that for suitable sequences of subgroups of Bianchi groups, including the standard exhaustive sequences of a congruence subgroup, and even symmetric powers of the standard representation of $\mathrm{SL }_2(\mathbb {C})$ the size of the torsion part in the first integral homology grows exponentially. This extends results of Bergeron and Venkatesh to a case of non-uniform lattices. Our approach is geometric. For odd symmetric powers we obtain a modified statement.     

Fluorescent Vesicles Consisting of Galactose‐based Amphiphilic Copolymers with a π‐Conjugated Sequence Self‐assembled in Water

Fluorescent vesicles considered as a mimic of natural primitive cells are prepared from poly(3‐hexylthiophene)‐block‐poly(3‐O‐methacryloyl‐D‐galactopyranose) P3HT‐b‐PMAGP copolymers. The unique characteristic of such vesicular nanostructures is their architecture, which comprises a hydrophobic π‐conjugated P3HT wall stabilized by a hydrophilic PMAGP interface featuring glucose units. The results of this work offer a very efficient and straightforward method for engineering well‐controlled fluorescent nanoparticles (without the addition of dyes), which provide an excellent support to the study of carbohydrate‐protein interactions.

     

Ueber die Bestimmung des Alters der Blutflecken

Ohne Zusammenfassung     

Acid-Catalyzed Transacetalization from Glycol to Pinacol Acetals

A one-pot transacetalization of glycol acetals, frequently used as protecting groups of the aldehyde function, into the more stable pinacol acetals is given. A clean transformation of aromatic and aliphatic substrates is possible with trifluoroacetic acid within 30 min at 0 °C. Glycol acetals derived from ketones (ketals) cannot be converted with this protocol. Deprotection of the pinacol acetals is possible with trifluoromethanesulfonic acid in the presence of water.