Gerhard Simchen

β-silylation of N-alkylpyrroles, experimental support of theoretical calculations

The β-substitution of N-alkylpyrroles which is “unusual” but predicted by theoretical calculations, was supported by the 1H-NMR and GC/MS analysis of the reaction products of 1-methylpyrrole-2,5-d2 (1a) with trimethylsilyl trifluoromethane-sulfonate (2) in triethylamine (3). Thus, 1a gives with 2 in 3 predominantly the β-isomer 5b (two deuteriums) and small amounts of the α-isomer 4a (one deuterium). The formation of these products of such a deuterium distribution evidently supports the results of theoretical calculations which indicate that the electron density is the major factor controlling the electrophilic substitution of N-alkylpyrroles with hard electrophiles. The thermodynamic stability of the α-substituted form I (Scheme 1) is assumed to be the second factor governing this reaction, since the α α β isomerization was conclusively ruled out.

Freidel-crafts acylation of 1-tert-butyldimethylsilylpyrrole, a very short and simple route to 3-substituted pyrroles.

Abstract 1-tert-Butyldimethylsilylpyrrole undergoes Freidel-Crafts acylation almost exclusively at β-position giving after sodium flouride supported hydrolysis the 3-pyrroloketones.

Über die H-D-austauschreaktion an N,N-dialkyl-formamidacetalen

Zusammenfassung N,N-Dialkyl-formamidacetale tauschen in O-deuterierten Alkoholen das Formylwasserstoffatom gegen Deuterium aus. Untersuchungen zum Reaktionsablauf lassen auf N-Ylide als Zwischenprodukte schliessen.

Synthese und struktur von N,N-bis(trimethylsilyl)trifluormethansulfonsäureamid

Abstract The reaction of trifluormethane sulfonic acid anhydride with hexamethyldisilazane in the presence of triethylamine yields the silylating reagent N,N -bis(trimethylsilyl)trifluormethane sulfonic acid amide 2 (monoclinic, P 2 1 / n , a = 871.4(2) pm, b = 1187.0(2) pm, c = 1423.5(3) pm, b = 97.164(8)°, Z = 4, wR 2 = 0.1199). The molecular structure shows strong intramolecular O-Si contacts of 289.8 pm, which can be interpreted by interaction of the oxygen centered electron pair with one of the σ * (Si-C) orbitals of the trimethylsilyl group. Due to a 1,3-trimethylsilyl shift in solution, two tautomeric forms are detected by NMR spectroscopy. The molar ratio of these isomeres depends strongly on the temperature of the solvent.

Synthesis of 2-(phenyltrifluoroacetylamino)-3-(trimethylsiloxy) alkanoic acid and N-phenyl-N-trifluoroacetyldehydroamino acid esters

Abstract Reaction of aromatic aldehydes 4 with the ketene acetal 3 in presence of zinc bromide affords methyl 2-(phenyltrifluoroacetylamino)-3-trimethylsiloxy-alkanoates 5 . Elimination of trimethylsilanole from 5 by means of trifluoroacetic acid anhydride yields (E,Z) methyl 2-(phenyltrifluoroacetyl-amino)-2-alkenoates 6 .

Orthoamide, LXII [1]. – Mikrowellen-unterst ¨ utzte Formylierung schwach CH2-acider Verbindungen mit dem Bredereck-Simchen Reagenz – Umwandlung der Kondensationsprodukte in Heteroaromaten / Orthoamides, LXII [1]. – Microwave Assisted Formylation of Weak CH2-Acidic Compounds with the Bredereck-Simchen Reagent – Preparation of Heteroaromatic Compounds from the Condensation Products

The diformylation of the dinitriles 4 and diesters 7 with the Bredereck-Simchen reagent HC[N(CH3)2]2[OC(CH3)3] (1) under microwave irradiation give the bis-enamines 6 and 8 with dramatically reduced reaction times and improved yields compared to conventional heating. The condensation products formed can be easily converted to bis-pyrazole and bis-isoxazole derivatives 13 and 20, respectively. Methyl anthranilate reacts on prolonged heating with the orthoamide 21 to give ketene aminal 23 in low yield (8 %). Under microwave irradiation the same reagents lead to a mixture of 23 (14 %) and dihydropyrane 24 (28 %).

Synthesen von Pyrido(2,3-d)- und Pyrimido-(4,5-d)-pyrimidinen : über eine Ketimin-Enamin-Tautomerie (Synthesen in der heterocyclischen Reihe ; 11)

4-Imino-1.3-dimethyl-5-methylaminomethylen-dihydrouracil (1) reagiert mit nucleophilen Agentien (Phenylhydrazin, Hydroxylamin und CH-aciden Verbindungen) an der CH-Gruppe am C-5 zu den 4-Imino-5-aminomethylen-Verbindungen 2, 3 bzw. unter Ringschlus zu Pyrido[2.3-d]pyrimidinen 4, 5, 6, und mit elektrophilen Agentien (Phenylisocyanat, Phenylsenfol) zu Pyrimido[4.5-d]pyrimidinen 7, 8. Bei vorsichtiger Benzoylierung von 1 entstehen zwei Tautomere 9a und 9b, die durch Umkristallisation ineinander ubergefuhrt werden konen. Mit uberschussigem Benzoylchlorid/Pyridin erfolgt in der Warme Ringschlus zum Pyrimido[4.5-d]pyrimidin 12.

Verfahren zur Herstellung von Komplexverbindungen aus Carbonsäureamiden und Dialkylsulfaten

Patentschrift Anmelder: Bredereck, Hellmut Anmeldeland: Deutschland Anmeldedatum: 27.12.1961 Publikationsland: Deutschland Publikationsdatum: 07.11.1963

Über Säureamid-Dialkylsulfat-Komplexe (Säureamid-Reaktionen ; 32)

Aus N.N-disubstituierten Carbonsaureamiden und Dialkylsulfaten entstehen reaktionsfahige O-Alkylkomplexe der Saureamide.