A one-pot, consecutive, four-component synthesis of 5-acylpyrid-2-ones initiated by Pd/cataCXium^® ABn catalysis proceeds under mild reaction conditions and in good yields, with a broad scope of three points of diversity. This sequence is superior to the initially proposed Pd/Cu-catalyzed version because all four components can be employed in close to stoichiometric amounts.

The Masuda borylation/Suzuki arylation (MBSA) sequence starting from N-protected 3-iodoindoles has successfully been extended to the coupling of five-membered heterocycles and indoles in the arylation step, which could not be achieved with previously developed MBSA methods. By this approach the one-pot nature of the method as well as the use of a simple catalyst system has been retained. The applicability of the method has been demonstrated by the facile synthesis of camalexins and 3,3′-biindoles, compounds of special interest due to their pronounced antifungal, antimicrobial and cytotoxic activities.

Sonogashira coupling and the catalytic Glaser coupling are both catalyzed by the Pd–Cu complex couple and can be concatenated to a consecutive sequentially Pd/Cu-catalyzed process in a one-pot fashion, and air oxygen serves as the only oxidant in the second step. In a pseudo-four-component synthesis, a broad variety of symmetrically substituted 1,4-bis(hetero)aryl-1,3-butadiynes are obtained in good to excellent yields. Interestingly, the presence of iodide ions has been found to be advantageous over other halides to trigger the Pd/Cu-catalyzed Glaser step, and Pd and Cu species, as well as triethylamine as a base, are prerequisite for both couplings, which proceed with higher efficiency if performed in a one-pot sequence.

Diazine-bridged bisindoles are readily obtained from N-Boc-protected 3-iodoindoles and 3-iodo-7-azaindole in a pseudo three-component reaction involving a one-pot Masuda borylation–Suzuki arylation sequence. Some of the title compounds display promising cytotoxic properties. The versatility of this methodology is illustrated by a very concise total synthesis of the marine alkaloid hyrtinadine A.

Phenothiazinyl merocyanine dyes with variable substitution patterns on the peripheral benzene ring were synthesized in good yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and N-methylrhodanine or indan-1,3-dione. The electronic properties were investigated by cyclic voltammetry, absorption, electro-optical absorption, and emission spectroscopy. All these merocyanines reveal reversible redox behavior that stems from the phenothiazinyl-centered oxidation to give stable radical cations. The redox potentials strongly correlate with Hammett σ_p parameters. All merocyanines reveal large Stokes shifts. They also display a pronounced emissive solvatochromism, which is caused by large dipole moment changes upon excitation from the ground to the excited state. These findings are supported by solvatochromism studies and time-dependent DFT computations.

2,4-Di- and 2,4,7-trisubstituted quinolines are readily synthesized in a regioselective fashion from acyl chlorides, terminal alkynes, and 2-aminothiophenols by a consecutive, microwave-assisted one-pot three-component Sonogashira coupling-Michael addition–cyclocondensation sequence and following sulfur extrusion in moderate to good yields. The terminal sulfur extrusion step was studied by DFT computations. The absorption spectra of 2,4-disubstituted quinolines can be rationalized by DFT-ZINDO-CI calculations and all derivatives show intense blue emission upon UV excitation.

Triethoxysilyl functionalized phenothiazinyl ureas were synthesized and immobilized by in situ synthesis into mesoporous hybrid materials. The designed precursor molecules influence the structure of the final materials and the intermolecular distance of the phenothiazines. XRD and N₂ adsorption measurements indicate the presence of highly ordered two-dimensional hexagonally structured functional materials, while the incorporation of the organic compounds in the solid materials was proved by means of ¹³C and ²⁹Si solid state NMR spectroscopy as well as by FT-IR spectroscopy. Upon oxidation with (NO)BF₄ or SbCl₅, stable phenothiazine radical cations were generated in the pores of the materials, which was detected by means of UV/Vis, emission, and EPR spectroscopies.

Summary: Monodisperse oligophenothiazines are rapidly synthesized in good yields by use of Suzuki arylation. These well defined oligomers reveal both highly fluorescence and low oxidation potentials. As a consequence of intense electronic coupling as supported by cyclic voltammetry a selected trimer shows hole-transport properties in a hole-conductor-only set-up of a diode with relatively low on-set voltage.

Linear, easily accessible alkyl and (hetero)aryl-substituted alkynyl allyl alcohols are readily and enantioselectively transformed into 2,7-dioxabicyclo[3.2.1]octanes by a sequential rhodium-catalyzed process. Based on the initial cycloisomerization, the in situ generated rhodium(I)-BINAP complex enables a subsequent reduction with hydrogen and the transformation into bicyclic frameworks.

Mesoporous hybrid materials of (oligo)phenothiazines covalently grafted onto MCM-41 or SBA-15 silica have been readily prepared from (oligo)phenothiazinyl carbamates. The phenothiazine precursors show interesting electronic properties according to electronic spectroscopy and cyclic voltammetry. The resulting electronically active hybrid materials display fluorescence and can be oxidized to give stable radical-cationic species upon mild oxidation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

3,5-Disubstituted and 1,3,5-trisubstituted pyrazoles are readily synthesized from acyl chlorides, terminal alkynes, and hydrazines by a consecutive one-pot three-component Sonogashira coupling/Michael addition/cyclocondensation sequence in good to excellent yields. These pyrazoles are highly fluorescent, both in solution and in the solid state. Investigation of the electronic properties by UV/Vis and fluorescence spectroscopy and by DFT and ZINDO CI computations reveal that the excited state is highly polar and allows fine-tuning of the absorption and emission properties. X-ray structure analyses of 3,5-disubstituted pyrazoles reveal self-organization by hydrogen bonding and π-stacking. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

2,4-Disubstituted benzodiazepines are readily synthesized in good yields from acyl chlorides, terminal alkynes, and benzene-1,2-diamines by a consecutive one-pot, three-component Sonogashira coupling/Michael addition/cyclocondensation sequence. These diazepines display intense solid-state fluorescence, but only weak emission in solution at room temperature. The absorption and emission maxima can be controlled by the substitution pattern. Upon cooling, however, the phenomenon of cryofluorescence can be observed. X-ray structure analysis and temperature-dependent NMR indicate that freezing out of conformational interconversions is the source of the thermochromicity observed upon UV excitation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

An alkynoyl ortho-iodo phenolester or alkynoyl ortho-iodo anilides and propargyl allyl ethers react under Sonogashira coupling conditions in the sense of an insertion–coupling–isomerization–Diels–Alder hetero domino reaction to furnish (tetrahydroisobenzofuran)-spirobenzofuranones and -spirodihydroindolones in good yields. Many representatives can be crystallized and single crystal structure analyses display steric and electronic substituent effects on the torsional angles of the terminal (hetero)aryl groups and the central cis,trans-butadiene fragment. DFT computations reveal that in the final pericyclic step the Diels–Alder termination is by far thermodynamically and kinetically favored over a possible Claisen rearrangement. Compounds of this new class of spirocyclic compounds possess large Stokes shifts and fluoresce intensively with blue over green to orange colors. As a consequence of the spirocyclic rigidity fluorescence lifetimes and quantum yields are rather high in some cases.

Alkinoyl ortho-iodphenolester oder Alkinoyl ortho-iodanilide und Propargylallylether reagieren unter den Bedingungen der Sonogashira-Kupplung im Sinne einer Insertions–Kupplungs–Diels–Alder-Hetero-Domino-Reaktion zu (Tetrahydroisobenzofuran)-spirobenzofuranonen bzw. -spirodihydroindolonen in guten Ausbeuten, von denen viele kristallisiert werden konnten. Die Einkristallstrukturanalysen offenbaren sterische und elektronische Substituenteneffekte auf die Torsionswinkel der terminalen (Hetero)arylgruppen und des zentralen cis,trans-Butadienfragments. DFT-Rechnungen zeigen, dass im letzten pericyclischen Schritt die Diels–Alder-Reaktion gegenüber einer möglichen Claisen-Umlagerung bei weitem thermodynamisch und kinetisch begünstigt ist. Viele Verbindungen dieser neuen Spirocyclenklasse besitzen große Stokes-Verschiebungen und fluoreszieren intensive mit blauer, grüner oder oranger Farbe. Als Folge der spirocyclischen Rigidität sind in einigen Fällen die Fluoreszenzlebensdauern und Quantenausbeuten relative hoch.

Starting from N-hexylphenothiazine, a versatile construction kit of brominated and borylated phenothiazines can be easily prepared by a sequence of bromination, bromo–lithium exchange/borylation, and Suzuki coupling. Subsequent Suzuki arylation of the building blocks gives soluble, monodisperse, and structurally well defined oligophenothiazines in good yields. The molecular weights at the peak maximum (M_p), obtained by GPC (gel permeation chromatography), and the actual molecular weights of the oligomer series, obtained by mass spectrometry, show excellent correlation. A QM/MM conformational analysis for the complete series reveals that the obvious butterfly-shaped phenothiazine structure multiplies and significantly reduces the hydrodynamic volume of the oligomers. The electronic properties (absorption and emission spectroscopy and cyclic voltammetry) give reasonable correlations with the chain length. With regard to the emission maxima, the effective conjugation length is already reached with the hexamer. Oligophenothiazines are highly fluorescent, with high fluorescence quantum yields, and are simultaneously highly electroactive, with low oxidation potentials.

Ausgehend von N-Hexylphenothiazin kann leicht ein vielseitiger Baukasten aus bromierten und borylierten Phenothiazinen über eine Sequenz aus Bromierung, Bromo–Lithium-Austausch/Borylierung und Suzuki Kupplung hergestellt werden. Die nachfolgende Suzuki-Arylierung der Bausteine führt in guten Ausbeuten zu löslichen, monodispersen und strukturtreuen Oligophenothiazinen. Die Molekulargewichte beim Peakmaximum (M_p), die aus GPC (Gelpermeationschromatographie) erhalten werden und die tatsächlichen Molekulargewichte der Oligomeren, erhalten durch Massenspektrometrie, ergeben eine exzellente Korrelation. Die QM/MM-Konformationsanalyse der gesamten Serie zeigt, das der Effekt der Schmetterlingsstruktur der Phenothiazine sich vervielfältigt und so das hydrodynamische Volumen der Oligomere deutlich verkleinert. Die elektronischen Eigenschaften der Oligomere (Absorptions- und Emissionsspektroskopie und Cyclovoltammetrie) korrelieren mit der Kettenlänge. Im Falle der Emissionsmaxima wird die effektive Konjugationslänge bereits mit dem Hexamer erreicht. Oligophenothiazine fluoreszieren mit hohen Fluoreszenzquantenausbeuten und erweisen sich gleichzeitig wegen ihrer niedrigen Oxidationspotenziale als äußerst elektroaktiv.