Christophe M. L. Vande Velde

Symmetrical and Nonsymmetrical Chromophores with Tröger’s Base Skeleton: Chiroptical, Linear, and Quadratic Nonlinear Optical Properties—A Joint Theoretical and Experimental Study

We report on the novel chiral push-pull chromophores derived from 6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (Trögers base skeleton). The synthesis of symmetrical chromophores featuring two identical acceptors, as well as the synthesis of unsymmetrical chromophores featuring only one acceptor is given. Symmetrical chromophores were prepared in the enantiomerically pure form and their chiroptical properties were investigated. Second-order nonlinear optical (NLO) properties of new chromophores were investigated with the aid of hyper-Rayleigh scattering (HRS). The detailed theoretical analysis of the second-order NLO properties of the chromophores was also undertaken. The joint theoretical and experimental studies of chromophores derived from Trögers base skeleton, in comparison with benchmark chromophores featuring a dimethylamino group as the donor, provided insight into the relationship between the structure of the new chromophores and their NLO properties.

Synthesis of functionalized pyridazin-3(2H)-ones via bromine-magnesium exchange on bromopyridazin-3(2H)-ones.

The potential of halogen-magnesium exchange reactions, followed by quenching with electrophiles, for the functionalization of the pyridazin-3(2H)-one core was investigated. 2-Benzyl-4-bromo-5-methoxy- (1), 2-benzyl-5-bromo-4-methoxy- (4), and 2-benzyl-4,5-dibromopyridazin-3(2H)-one (10) were selected as readily available model substrates. While 1 and 10 gave exclusively C-4 metalation, a tandem reaction involving nucleophilic substitution via addition elimination and bromine-magnesium exchange was observed with 4.

Synthesis of polycyclic spiroindolines by highly diastereoselective interrupted Ugi cascade reactions of 3-(2-isocyanoethyl)indoles

We report a highly diastereoselective interrupted Ugi reaction to construct a broad range of structurally congested and stereochemically complex spiroindolines from tryptamine-derived isocyanides. The reaction is facilitated by using fluorinated alcohols (TFE or HFIP) as solvents and tolerates a broad range of amines, aldehydes and 2-isocyanoethylindoles to give polycyclic products in moderate to excellent yields.

(E,E)-2,5-Dipropoxy-1,4-bis[2-(2,4,6-trimethoxyphenyl)ethenyl]benzene.

The title compound, C30H34O8, crystallizes in the space group P-1 with one-half of a molecule in the asymmetric unit. A three-dimensional network is generated by OCH3...pi and CH...pi interactions. The conformation of the C-C bond exocyclic to the central benzene ring is different from that of every other known derivative. A comparison of the geometry of the title molecule and of its solid-state structure with other 2,4,6-trimethoxy-substituted PPV [i.e. poly(p-phenylenevinylene)] oligomers, in particular the isopropoxy-substituted compound, is provided.

Mononuclear heteroleptic complexes of copper(I) with 5-phenyl-2,2′-bipyridine and triphenylphosphine: crystal structures, Hirshfeld surface analysis and luminescence properties

The reaction of 5-phenyl-2,2′-bipyridine (L) with a mixture of CuCl or CuBr and PPh3 leads to the formation of mononuclear heteroleptic complexes [CuL(PPh3)Cl] (1) and [CuL(PPh3)Br] (2). According to X-ray diffraction, 1 and 2 crystallize in the triclinic P and orthorhombic Pbca space groups, respectively. The structure of 1 contains four independent molecules in the asymmetric unit. Both structures reveal that each tetracoordinated copper(I) atom is linked to the two nitrogen atoms of L, one halogen and one PPh3 with the formation of a slightly distorted trigonal pyramidal coordination core. Both structures are additionally stabilized by weak intramolecular π⋯π stacking interactions formed between the terminal pyridine fragments of two ligands L corresponding to two adjacent molecules. Hirshfeld surface analysis showed that the structures of both complexes are highly dominated by H⋯H and H⋯C contacts and also characterized by H⋯Hal, C⋯C, H⋯N and C⋯N contacts. Both 1 and 2 were found to be emissive in the solid state at 298 K, with maxima at 596 and 610 nm, respectively, due to a (M + Hal)LCT excited state. The observed blue-shifting of the emission maximum of 1 and 2 compared to that of the previously reported [CuL(PPh3)I] can be explained by the replacement of the iodide by a weaker electron-donating bromide and chloride, respectively, lowering the HOMO energy level, less influencing the LUMO energy, and thus resulting in an increase of the HOMO–LUMO energy gap. This explanation is further supported by comparison with the recently reported emission maxima at 630 and 575 nm of the closely related complexes, namely [CuL(PPh3)I] and [CuL(PPh3)2]BF4, respectively. The emission maxima of 1, 2 and [CuL(PPh3)I] are slightly (12–16 nm) shifted to longer wavelengths when the temperature was lowered to 77 K.

(E, E)-2,5-Dimethoxy-1,4-bis[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene

In the title compound, C30H34O8, molecular symmetry is coincident with crystallographic inversion symmetry. A three-dimensional network is generated containing both C-H...pi and C-H...n(O) interactions. A comparison of the geometry of this molecule and the structure of a number of 2,4,6-trimethoxy-substituted analogues is provided.

Racemic 1,2,3,4,7,8,9,10-octa-fluoro-6H,12H-5,11-methano-dibenzo[b,f][1,5]diazo-cine: an octa-fluorinated analogue of Tröger's base.

The title compound, C15H6F8N2, possesses a non-crystallographic twofold axis. The dihedral angle between the two benzene rings is 98.4 (2)°. The crystal structure involves intermolecular C—H⋯F hydrogen bonds.

2,6-Di(arylamino)-3-fluoropyridine Derivatives as HIV Non-Nucleoside Reverse Transcriptase Inhibitors

New non-nucleoside reverse transcriptase inhibitors (NNRTI), which are similar in structure to earlier described di(arylamino)pyrimidines but featuring a 2,6-di(arylamino)-3-fluoropyridine, 2,4-di(arylamino)-5-fluoropyrimidine, or 1,3-di(arylamino)-4-fluorobenzene moiety instead of a 2,4-disubstituted pyrimidine moiety, are reported. The short and practical synthesis of novel NNRTI relies on two sequential Pd-catalyzed aminations as the key steps. It is demonstrated through direct comparison with reference compounds that the presence of a fluorine atom increases the in vitro anti-HIV activity, both against the wild type virus and drug-resistant mutant strains.

Stereoselective Synthesis of Functionalized Bicyclic Scaffolds by Passerini 3-Center-2-Component Reactions of Cyclic Ketoacids

We report the use of bifunctional starting materials (ketoacids) in a diastereoselective Passerini three‐center‐two‐component reaction. Study of the reaction scope revealed the required structural features for stereoselectivity in the isocyanide addition. In this system, an interesting isomerization of the primary Passerini product – the α‐carboxamido lactone – into an atypical product, an α‐hydroxy imide, was found to occur under acidic conditions. Furthermore, enantioenriched Passerini products can be generated from an enantioenriched ketoacid obtained by chemoenzymatic synthesis.

Asymmetrically substituted distyrylbenzenes and their polar crystal structures

The synthesis of twelve asymmetric donor–acceptor distyrylbenzene derivatives with either one nitrile group or one, two or three nitro groups as electron acceptors, and one, two or three methoxy groups as electron donors is reported. Peak potentials obtained from cyclic voltammetry were combined with experimental UV/Vis data and molecular dipole moments obtained from quantum chemical calculations, yielding insight into the influence of the positions of the substituents on the electronic structure and charge distribution of this as yet unexplored class of organic semiconductors. The supramolecular structures of five of these compounds have been studied using single-crystal X-ray diffraction to monitor the influence of the positions of donor and acceptor groups on the organisation of the molecules in the solid state, and three crystal structures have been identified in which the molecular dipoles do not organize themselves in a centrosymmetric lattice. Analysis of the dipoles in the unit cell yields further insight into the possible non-linear optical properties of these three polar structures.