Dimethylzinc-mediated alkynylation of imines

The treatment of various aromatic and aliphatic aldimines with a mixture of a terminal alkyne and a commercially available dimethylzinc solution in toluene yields the corresponding protected propargylic amines in moderate to excellent yields. The reaction proceeds in the absence of any activator. These observations led to the development of a three-component synthesis of propargylic amines in which the product was obtained upon mixing an aldehyde with ortho-methoxyaniline and phenylacetylene in the presence of dimethylzinc, through in situ formation of the corresponding imine.     

Design of BODIPY dyes as triplet photosensitizers: electronic properties tailored for solar energy conversion,photoredox catalysis and photodynamic therapy

BODIPYs are renowned fluorescent dyes with strong and tunable absorption in the visible region, high thermal and photo-stability and exceptional fluorescence quantum yields. Transition metal complexes are the most commonly used triplet photosensitisers, but, recently, the use of organic dyes has emerged as a viable and more sustainable alternative. By proper design, BODIPY dyes have been turned from highly fluorescent labels into efficient triplet photosensitizers with strong absorption in the visible region (from green to orange). In this perspective, we report three design strategies: (i) halogenation of the dye skeleton, (ii) donor–acceptor dyads and (iii) BODIPY dimers. We compare pros and cons of these approaches in terms of optical and electrochemical properties and synthetic viability. The potential applications of these systems span from energy conversion to medicine and key examples are presented.

BODIPYs offer a versatile platform to build organic triplet photosensitisers for PDT, TTA upconversion and photocatalysis. Tuning their properties provides the opportunity of replacing heavy-metal complexes and can lead to improved sustainability.     

Enzyme‐Catalyzed Crosslinking in a Partly Frozen State: A New Way to Produce Supermacroporous Protein Structures

In this study a new way to produce supermacroporous protein structures was investigated. Enzyme‐mediated crosslinking of gelatin or casein was performed in a partly frozen state, which yielded stable, protein‐based cryogels. The reaction kinetics for the formation of cryogels were found to be fairly slow, most likely due to the low temperature (?12 °C) used or due to an increased viscosity owing to the cryo‐concentration taking place. The produced cryogels were characterized with regards to their physical properties and in vitro degradation. Furthermore, cryogels produced from gelatin and casein were evaluated as potential scaffolds by fibroblast cultivation to confirm their in vitro biocompatibility. Gelatin‐ and casein‐based scaffolds both supported cell proliferation and migration through the scaffold.

     

A new method for determination of flourine by means of the alteration of glass-surface

The new method to determine F^- is based on the alteration of the glass surface which possesses no wettability when it is dipped into chromic acid cleaning mixture containing HF. The drop of chromic mixture which forms on the glass surface has a convexity depending upon F^- concentration.Measures of the contact angle not directly of this drop but of an bubble (captive bubble) which appears at a bottom of a glass tube. into the test solution, are carried out. Approprriate devices allow even the microdetermination of fluorine. Boric acid and silicic acid are the only reagents able to affect the accuracy of this method.     

Synthesis of some oligopyridine-galactose conjugates and their metal complexes: a simple entry to multivalent sugar ligands

Some galactose-oligopyridine conjugates were readily assembled by combining differently functionalized oligopyridines with peracetylated galactose derivatives. Variation in the structure of the components and of the linkers employed for their connection afforded adducts of different size, shape, and conformational mobility. Complexation of the bipyridine ligands with CuOTf and of the terpyridine ligand with Zn(OTf)₂ afforded the corresponding peracetylated 2:1 and 1:1 complexes, respectively, as single species. Their structures were determined to be tetrahedral (Cu complexes) and trigonal-bipyramidal (Zn complex), on the basis of spectroscopic evidence. Removal of the acetyl protecting groups from the ligands afforded the corresponding polyols. The terpyridine-Zn(II) complex, unlike the bipyridine-Cu(I) complexes maintained their structures upon removal of the acetyl protecting groups.     

Synergy,Compatibility, and Innovation: Merging Lewis Acids with Stereoselective Enamine Catalysis

In recent years there has been an accelerated rate of development in the field of organocatalysis, with asymmetric organocatalysis now reaching full maturity. The invention of new organocatalytic reactions and the exploration of new concepts now appear in tandem with the application of organocatalytic techniques in the synthesis of natural products and active pharmaceutical ingredients (APIs). After a “golden rush” in organocatalysis, researchers are now starting to combine different methods, thereby taking advantage of the significant benefits of synergy. Metals are used in combination with organocatalytic processes, thus reaching complexity that is found in nature, where enzymes take advantage of the presence of certain metals to increase the arsenal of organic transformations available. In this Focus review, we illustrate the possibility of a “happy marriage” between Lewis acids and organocatalytic stereoselective processes. Questions have been raised about the combination of Lewis acids and organocatalysis owing to the presence of water and/or strong bases in these processes. Some Lewis acids have been shown to be compatible with organocatalysis and concepts relating to their use will be illustrated herein. To summarize the fruitful use of Lewis acids in stereoselective organocatalytic processes, we will draw attention to the advantages and selectivity achieved using this method.