Trimethylsilyl cyanide promoted cyanation of tertiary alkyl chlorides and other SN1 active compounds

Trityl isocyanide as a general reagent for visible light mediated photoredox-catalyzed cyanations

A photoredox catalytic strategy has been developed to enable the functionalization of a variety of commercially available, structurally different radical precursors by the use of a bench-stable isonitrile as an efficient cyanating reagent. Specifically, a radical-based reaction has provided a mild and convenient procedure for the cyanation of primary, secondary and tertiary radicals derived from widely accessible sp3-hybridized carboxylic acids, alcohols and halides under visible light irradiation. The reaction tolerates a variety of functional groups and it represents a complementary method for the cyanation of structurally different scaffolds that show diverse native functionalities, expanding the scope of previously reported methodologies.

Modulation of γ-Secretase Activity by a Carborane-Based Flurbiprofen Analogue

All over the world, societies are facing rapidly aging populations combined with a growing number of patients suffering from Alzheimer's disease (AD). One focus in pharmaceutical research to address this issue is on the reduction of the longer amyloid-β (Aβ) fragments in the brain by modulation of γ-secretase, a membrane-bound protease. R-Flurbiprofen (tarenflurbil) was studied in this regard but failed to show significant improvement in AD patients in a phase 3 clinical trial. This was mainly attributed to its low ability to cross the blood-brain barrier (BBB). Here, we present the synthesis and in vitro evaluation of a racemic meta-carborane analogue of flurbiprofen. By introducing the carborane moiety, the hydrophobicity could be shifted into a more favourable range for the penetration of the blood-brain barrier, evident by a logD7.4 value of 2.0. Furthermore, our analogue retained γ-secretase modulator activity in comparison to racemic flurbiprofen in a cell-based assay. These findings demonstrate the potential of carboranes as phenyl mimetics also in AD research.

Copper-Catalyzed Tertiary Alkylative Cyanation for the Synthesis of Cyanated Peptide Building Blocks

In this paper, we report efficient cyanation of various peptides containing the α-bromocarbonyl moiety using a Cu-catalyzed radical-based methodology employing zinc cyanide as the cyanide source. Mechanistic studies revealed that in situ formed CuCN was a key intermediate during the catalytic cycle. Our method could be useful for the synthesis of modified peptides containing quaternary carbons.

Design, synthesis, and application of tartaric acid derived N-spiro quaternary ammonium salts as chiral phase-transfer catalysts

A novel class of tartaric acid-derived N-spiro quaternary ammonium salts was synthesised starting from known TADDOLs. These compounds were found to catalyse the asymmetric α-alkylation of glycine Schiff bases with high enantioselectivities and in good yields.

Farewell to the HSAB treatment of ambident reactivity

The concept of hard and soft acids and bases (HSAB) proved to be useful for rationalizing stability constants of metal complexes. Its application to organic reactions, particularly ambident reactivity, has led to exotic blossoms. By attempting to rationalize all the observed regioselectivities by favorable soft-soft and hard-hard as well as unfavorable hard-soft interactions, older treatments of ambident reactivity, which correctly differentiated between thermodynamic and kinetic control as well as between different coordination states of ionic substrates, have been replaced. By ignoring conflicting experimental results and even referring to untraceable experimental data, the HSAB treatment of ambident reactivity has gained undeserved popularity. In this Review we demonstrate that the HSAB as well as the related Klopman-Salem model do not even correctly predict the behavior of the prototypes of ambident nucleophiles and, therefore, are rather misleading instead of useful guides. An alternative treatment of ambident reactivity based on Marcus theory will be presented.