Photo/thermochromic macrocycles based on dihydroazulenes,dithienylethenes, and spiropyrans

Suitably functionalized dihydroazulenes (DHAs), dithienylethenes (DTEs), and spiropyrans (SPs) are photo-active molecules that upon irradiation undergo isomerization by ring-opening/closure reactions, which involve carbon-carbon or carbon-heteroatom bond formation/breakage. These photo-isomers may return to the original ones under light or thermal activation. Introducing molecular photoswitches into macrocyclic structures can have strong implications for the forward and backward switching properties. In this report we summarize synthetic protocols for making macrocycles based on one or more units of DHA, DTE, and SP and the resulting properties of these macrocycles.     

Vinyl Sulfonate Esters: Efficient Chain Transfer Agents for the 3D Printing of Tough Photopolymers without Retardation

The formation of networks through light‐initiated radical polymerization allows little freedom for tailored network design. The resulting inhomogeneous network architectures and brittle material behavior of such glassy‐type networks limit the commercial application of photopolymers in 3D printing, biomedicine, and microelectronics. An ester‐activated vinyl sulfonate ester (EVS) is presented for the rapid formation of tailored methacrylate‐based networks. The chain transfer step induced by EVS reduces the kinetic chain length of the photopolymer, thus shifting the gel point to higher conversion, which results in reduced shrinkage stress and higher overall conversion. The resulting, more homogeneous network is responsible for the high toughness of the material. The unique property of EVS to promote nearly retardation‐free polymerization can be attributed to the fact that after the transfer step no polymerizable double bond is formed, as is usually seen in classical chain transfer agents. Laser flash photolysis, theoretical calculations, and photoreactor studies were used to elucidate the fast chain transfer reaction and exceptional regulating ability of EVS. Final photopolymer networks exhibit improved mechanical performance making EVS an outstanding candidate for the 3D printing of tough photopolymers.     

Synthesis of potential HIV integrase inhibitors inspired by natural polyphenol structures

Drawing inspiration from the structural features of some natural polyphenols, the synthesis of two different model compounds as potential inhibitors of HIV integrase (IN) has been described. The former was characterised by a diketo acid (DKA) bioisostere, such as a β-hydroxycarbonyl moiety, between two fragments containing aromatic groups, while in the latter an epoxide linked two polyoxygenated aromatic residues. The moieties present in the structures are thought to function by chelating divalent metal ions on the enzyme catalytic site. Overall, 10 compounds were prepared and some of that submitted to molecular modelling studies (to investigate their interactions with the active site of IN), to metal titration studies (to detect their chelating capability) and to biological assays.     

[RuCl3ind3] and [RuCl2ind4]: Two New Ruthenium Complexes derived from the Tumor‐inhibiting RuIII Compound HInd (OC‐6‐11)‐[RuCl4ind2] (ind = indazole)

Indazolium (OC‐6‐11)‐tetrachlorobis(indazole) ruthenate(III), HInd (OC‐6‐11)‐[RuCl₄ind₂], exhibits excellent results in different tumor models in vitro and in vivo. Substitution reactions of this ruthenium(III) complex are of special interest for a deeper understanding of its interactions with biologically occurring targets and its mode of action. The indazolium complex salt can be transformed to the neutral, meridionally configurated trisindazole complex (OC‐6‐21)‐[RuCl₃ind₃] in solvents like tetrahydrofuran. The X‐ray crystal structure of this complex could be solved (monoclinic space group P2(1)/n, a = 12.441(3), b = 10.415(3), c = 21.635(4) Å, β = 105.02(1)°). In spite of the paramagnetic Ru^III atom most of the coordinated indazole protons could be assigned with the help of two‐dimensional NMR experiments. Additionally, a reduced reaction product of HInd (OC‐6‐11)‐[RuCl₄ind₂] in the physiological solubilizer 2‐pyrrolidone could be isolated and the X‐ray crystal structure of this Ru^II complex, (OC‐6‐12)‐[RuCl₂ind₄], crystallized with two 2‐pyrrolidones, could be solved (monoclinic space group P2(1)/n, a = 12.139(2), b = 10.426(2), c = 14.426(3) Å, β = 100.06(3)°).     

The reaction of β-aminoenones with substituted acetonitriles. Regiospecific synthesis of 2(1H)-pyridones

Unsymmetrically substituted β-aminoenones react with malononitrile, cyanomethylphenylsulfone, benzoyl-acetonitrile and ethyl cyanoacetate, in very mild conditions, to yield regiospecifically 3-functionalized 2(1H)-pyridones in high yields.     

Enantioselective radical cyclisation reactions of 4-substituted quinolones mediated by a chiral template

Six 4-substituted quinolones 6-8, which bear an ω-iodoalkyl chain, were prepared and subjected to reductive radical cyclisation conditions employing BEt(3)/O(2) as the initiator and either Bu(3)SnH or TMS(3)SiH as hydride source. 4-(4-Iodobutyl)-quinolone (6a) and 4-(3-iodopropylthio)-quinolone (8a) gave the respective 6-endo-cyclisation products in good yields. 4-(3,3-Dimethyl-4-iodobutyl)-quinolone (6b) cyclised in a 5-exo-fashion, while the other substrates delivered only reduction products. The cyclisation reactions could be conducted in the presence of a chiral template (1) with high enantiomeric excess (94-99% ee). The association behaviour of substrate 6a to 1 was studied by NMR titration experiments. In the enantioselective cyclisation of 6b a significant nonlinearity was observed when comparing the product ee with the ee of the template.