Ludwig Pfeuffer

New structural aspects of 3-vinyl-1H-indoles for predicting the outcome of Diels-Alder reactions

SummarySome selected 3-vinyl-1H-indoles have been synthesised and the first13C-NMR studies performed; in addition He(Iα) photoelectron spectra and the results of perturbation MO calculations of some examples of this class of compounds are presented. The molecular characteristics obtained thereby can be used to predict the results of [π4s+π2s]-cycloaddition reactions with 3-vinylindoles.ZusammenfassungAn selektiv synthetisierten 3-Vinyl-1H-indolen werden erstmals13C-NMR-spektroskopische Studien durchgeführt und exemplarisch an einigen Vertretern dieser Strukturklasse He(Iα)-Photoelektronenspektren sowie Ergebnisse von Störungs-MO-Rechnungen vorgestellt. Die daraus gewonnenen Moleküleigenschaften können zur Vorhersage des Reaktionsausganges von [π4s+π2s]-Cycloadditionen mit 3-Vinylindolen verwendent werden.

New [4+2]-cycloadditions of in situ generated indolyl enol ethers as heterocyclic donor-activated 1,3-dienes to carbazole derivatives

The ambident alkoxy-indolyl-methylcarbenium ions 1a–c are deprotonated by NaH to give in situ generated enol ethers which can be easily trapped by a dienophile such as, e.g., dimethyl acetylenedicarboxylate to form the carbazole derivatives 3, 4, and I. On reaction with the ethoxy-2-methylindolylcarbenium ion 1d under the same conditions, a stereoselective Michael-type addition with formation of 6 takes place.

Wittig-Olefinierung zu neuen donor- und akzeptor-substituierten 3-Vinylindolen: Optimierte Syntheseverfahren

SummaryThe optimized Wittig reaction of selectively functionalized 3-acylindoles yield new, and for Diels-Alder reactions highly reactive donor- and acceptor substituted 3-vinylindoles, respectively.

Selektive Synthesen zu 1′-aryl-, 1′-hetaryl-und 1′-alkylsubstituierten 3-Vinylindolen

Selective methods for deriving 1′-aryl-, 1′-indolyl-, 1′-pyrrolyl- and 1′-methyl-substituted 3-vinylindoles2 are described. In all cases the precursors were 3-acylindoles. The new compounds are synthetically useful synthons for annelation of the indole skeleton.

DIELS-ALDER-REAKTIONEN VON VINYLINDOLEN MIT ARIN UND 1,4-BENZOCHINONEN : NEUE POTENTIELLE DNA-INTERKALATOREN

SummaryDiels-Alder reactions of 2- and 3-vinylindoles with aryne, 1,4-benzo- and 1,4-naphtho-quinone lead to new six-ring annellated carbazoles. Molecular modeling studies predict that the compounds with coplanar framework are able to intercalate with the B-DNA.

Zur Struktur der Produkte der Reaktion vonE/Z-1-Benzolsulfonyl-3-(1-pentenyl)-indol mit N-Phenylmaleinimid: Ein erster Beitrag zur Konfigurations- und Konformationsanalyse in der Vinylindol-Cycloadditionsreihe

The products2,3 of the reaction ofE/Z-1-benzenesulfonyl-3-(1-pentenyl)-indole (1) and N-phenylmaleimide were analysed by1H-NMR spectroscopy. Exemplarily, the structure elucidation of theendo-cyclo-adduct2 b was achieved by using several NMR techniques (diff. NOE-, INDOR-measurements, decoupling experiments, spectra simulation). The1H-NMR-spectroscopically gained prediction of relative configuration and conformation of2 b was supported on X-ray analysis. The cyclohexene ring of the new cycloadducts adopts in the liquid phase and in the crystal a slightly twisted boat conformation.

Zur Reaktion vonE/Z-N-Benzolsulfonyl-3(2-methoxyvinyl)-indol mit Carbo- und Heterodienophilen: NeueDiels-Alder-Addukte aus der Indol- bzw. Carbazol-Reihe, V

E/Z-Benzenesulfonyl-3(2-methoxyvinyl)-indole1 reacts viaDiels-Alder type mechanism with dimethyl acetylendicarboxylate, N-phenyltriazolindione and diethyl mesoxalate to give new cycloadducts2–5 with [b]annellated indole structures.

The structures of indoiyl(alkoxy)carbenium tetrafluoroborates: a new class of highly stabilized carbenium ions

The conformations of and charge distributions in indolyl(alkoxy)carbenium tetrafluoroborates 2, a new class of highly stabilized carbenium ions, were investigated by 1H and 13C NMR spectroscopy and the crystal structure of indol-3-yl(methoxy)phenylcarbenium tetrafluoroborate (2e) was determined by X-ray diffraction methods. The phenyl-substituted cation of 2e exhibits axial chirality in the crystalline state