Katalytische Effekte bei den Reaktionen von 2,4-Dinitrofluorbenzol und 2,4-Dinitrochlorbenzol mit p-Anisidin in Benzol. 5. Mitteilung über nucleophile aromatische Substitutionsreaktionen

(1) The rates of the reactions of 2.4-dinitrofluorobenzene and 2.4-dinitrochlorobenzene with p-anisidine have been measured in benzene solution, with and without the addition of pyridine and 1.4-diaza-[2.2.2]-bicyclooctane (DABCO) as catalysts.     

Katalytische Effekte bei den Reaktionen von 2, 4-Dinitrofluorbenzol mit Benzylamin und N-Methylbenzylamin in Benzol. 6. Mitteilung über nucleophile aromatische Substitutionsreaktionen

• (1) The rates of reaction of 2,4-dinitrofluorobenzene with benzylamine and with N-methylbenzylamine have been measured in benzene solution, with and without the addition of pyridine or 1, 4-diaza-bicyclo[2.2.2]octane (DABCO) as catalyst.
• (2) Both reactions are catalyzed by the reacting amine, by pyridine and by 1, 4-diaza-bicyclo[2.2.2]octane.
• (3) Whereas the dependence on base concentration is linear in the case of N-methyl-benzylamine, the rate constants are curvilinearly related to base concentration in the reaction with benzylamine. Steric effects are shown to be responsible for this different behaviour, which is easily understood in terms of the two-step intermediate mechanism (eq.1) for nucleophilic aromatic substitutions.
• (4) Part of the pyridine catalysis has to be attributed to a medium effect, as can be shown directly in the reaction involving benzylamine.
• (5) The sensitivity of both reactions to base catalysis is much greater than that of the reaction of piperidine with 2, 4-dinitrofluorobenzene, but is found to be considerably smaller than in the reaction of p-anisidine with the same substrate, thus suggesting a correlation between the basicity of the reacting amine and the sensitivity of the reaction to base catalysis.

     

Der Einfluss von Dimethylsulfoxid und Dioxan auf die Reaktionen von 2,4-Dinitrofluorbenzol und 2,4-Dinitrochlorbenzol mit Piperidin in Benzol. 4. Mitteilung über nucleophile aromatische Substitutionsreaktionen

(1) The rates of the reactions of 2,4-dinitrofluoro- and 2,4-dinitrochlorobenzene with piperidine as influenced by the addition of dimethylsulfoxide and p-dioxane have been measured in benzene solution.     

Magnetische Kernresonanz-Untersuchungen über die Struktur der Komplexe aus Nitroaromaten mit aromatischen aminen 10. Mitteilung über nucleophile aromatische Substitutionsreaktionen [1]

1. NMR. and visible spectra of the addition products of N,2,4,6-tetranitro-N-methyl-aniline, 2,4,6-trinitrochlorobenzene, and 2,4-dinitro-6-cyano-chlorobenzene with aromatic amines (1-naphthylamine, N-mono- and -di-methyl-1-naphthylamine, 5-aminotetralin, N-methylaniline) demonstrate that electron donator-acceptor complexes (π-complexes) are formed.     

Magnetische Kernresonanz- und «Molecular Orbital»- untersuchungen über die struktur von MEISENHEIMER-komplexen 8. Mitteilung über nucleophile aromatische Substitutionsreaktionen [1]

(1) The NMR. spectra of the stable methoxide addition complexes of 2,4-dinitro-, 2,4,6-trinitro- and 2,4-dinitro-6-cyano-anisole, and the intramolecular (spiro) reaction product of 1-(2′-hydroxyethoxy)-2,4,6-trinitrobenzene demonstrate that these products are MEISENHEIMER (σ?) complexes (addition of base in position 1).     

Magnetische Kernresonanz-Untersuchungen über die struktur der Komplexe aus Nitroaromaten mit azid-ionen 9. Mitteilung über nucleophile aromatische Subsitutionsreaktionen [1]

1. NMR. spectra of solutions of tetraethylammonium azide and 2,4,6-trinitro;benzene derivatives (methyl picrate, picryl chloride and picryl azide, respectively) demonstrate that the reactants probably form σ complexes.     

Kinetische Untersuchungen über Substitutionsreaktionen an Metallkomplexen. 7. Mitteilung [1]. Kinetik und Mechanismus der Reaktion von Methoxyorganylcarbenpentacarbonyl-chrom-Verbindungen mit tertiären Phosphinen

The kinetics of the reactions of methoxyorganylcarbenechromium complexes Cr(CO)₅C(OCH₃)R′ (R′ = CH₃, C₆H₅) with tertiary phosphines PR₃ have been studied by means of spectrophotometric methods. The reaction products of general composition cis-Cr(CO)₄(PR₃)C(OCH₃)R′, Cr(CO)₅PR₃ and trans-Cr(CO)₄(PR₃)₂ are formed by cleavage of both the Cr-CO and the Cr-C(carbene) bonds. The two-term rate law indicates two parallel, dissociative and associative, mechanisms. The kinetic data will be discussed in connection with the concept of labilising and non-labilising ligands.     

Kinetische Untersuchungen über Substitutionsreaktionen an Metallkomplexen. 9. Mitteilung [1]. Kinetik und Mechanismus der Reaktion von Hexamethylborazolchrom-tricarbonyl mit tertiären Phosphinen und Phosphiten [2]

Hexamethylborazolechromium tricarbonyl B₃N₃(CH₃)₆ Cr(CO)₃ reacts with tertiary phosphines and phosphites under surprisingly mild conditions by cleavage of the ring-to-metal bond. For L = trialkylphosphines and trialkyl- or triaryl-phosphites, compounds of the general composition cis-Cr(CO)₃L₃ are formed, whereas for L = triphenyl- and tricyclohexyl-phosphine the complexes trans-Cr(CO)₄L₂ are obtained. The kinetics of the reaction of B₃N₃(CH₃)₆ Cr(CO)₃ with phosphites P(OR)₃ (R = CH₃, C₂H₅, C₆H₅) have been studied by means of spectrophotometric methods. The second-order rate law indicates a primary, rate-determining attack of the phosphite to either the metal atom or the ring ligand of the borazole complex. This attack is favoured by an extremely low activation energy. The mechanism of the substitution process is discussed in detail, and the reactivity of the hexamethylborazole compound is compared with that of other half-sandwich type complexes.     

Zur Reaktion von monosubstituierten Epoxypropanen mit Benzylamin. 1. Mitteilung über Ringöffnungsreaktionen kleiner Ringe

Reaction of monosubstituted epoxypropanes with benzylamine The reaction of the epoxides of the general formula with benzylamine at 40, 50 and 60°C has been examined. The determination of rate constants by variation of X has shown, that in the case of X = S or N no anchimeric acceleration occurred. These results have been approved by product analysis and by synthesis of the possible reaction products. Transition states of the epoxide/benzyl-amine reaction are discussed by means of the experimentally determined activation energy and activation entropy.     

Über die Synthese von Verbindungen mit dem Skelett der Homoproaporphine. 7. Mitteilung über natürliche und synthetische Isochinolinderivate

The synthesis of the tetracyclic spiro compounds 11, 12, 13, 14, 17, 18, 19 and 20 with homoproaporphine skeleton is described. Crucial intermediates are the secondary alcohols 10 and 16 . The structure of the spiro compounds is proved by transformation of 11 into the dihydronaphthalene derivative 24 and NMR.-spectroscopic studies of the latter.     

Notiz über die Reaktion von Methylhydrazin mit N-Cyano-azomethinen. Abhängigkeit des Reaktionsverlaufs von der Natur der Abgangsgruppe

The reaction of methylhydrazine with N-cyanoazomethines 1 containing a thioalkyl leaving group yields the 3-amino-1,2,4-triazole derivatives 2 , whereas the N-cyanoazomethines 1 containing an alkoxy leaving group give the isomeric 5-amino-1,2,4-triazoles 3. The yields are excellent and the position selectivity is high. The structures of the 1,2,4-triazole derivatives were determined with the aid of proton-coupled ¹³C-NMR. spectra.     

Eine neue Amidinsynthese mit Hilfe der Grignard-Reaktion. 7. Mitteilung über Grignard-Reaktionen [1]

In an unusual manner benzonitrile 5 and the substituted benzonitriles 1 , 14 reacted with benzylmagnesiumhalides to yield, besides dibenzyl, the amidines 7 , 13 , 15 , substituted on the imide nitrogen by a 1,2-diphenyl-vinyl group. The proposed structures are based on NMR. and mass spectra.     

Die Aminoalkylierung von Chinazolinen und Chinazolonen mit Hilfe der GRIGNARD-Reaktion. 5. Mitteilung über GRIGNARD-Reaktionen mit Halogenalkyliminen [2]

Quinazoline is aminoalkylated at C(4) by 3-dimethylaminopropyl-magnesium-chloride in preparative yield to give 3 , and by oxidation 5 , just as aryl and alkyl-magnesiumbromide give 15 , 19 , and 22 . These 4-substituted quinazolines yield by further treatment with the same GRIGNARD compound by 3, 4 or 1, 2-addition 3, 4-di-hydro-quinazolines ( 12 , 16 ) and 1, 2-dihydro-quinazolines ( 13 , 17 , 20 , 23 ), the latter being formed exclusively when the 4-position in the quinazoline is occupied by bulky residues; only the later can be oxidised to give 2,4-disubstituted aromates (cf 14 , 18 , 21 , 24 ). The spectroscopic and physicochemical behaviour of the dihydro compounds and the aromatic and the aromatic compounds are discussed.     

Die Aminoalkylierung von Phtalazinen und Phtalazonen mit Hilfe der GRIGNARD-Reaktion. 4. Mitteilung über GRIGNARD-Reaktionen mit Halogenalkylaminen [1]

Phtalazines and 4(3H)-phthalazones are aminoalkylated in high yield by 3-dimethylaminopropyl-magnesiumchloride. Phthalazines add only one molecule of the GRIGNARD reagent at the C?N-double bond, giving mono-aminoalkylated 1,2-dihydrophthalazines which undergo no further reaction without previous oxydation. Phthalazones react with the carbonyl and the C?N-group yielding in one step di-aminoalkylated dihydrophthalazines. The dihydrophthalazines are easily oxydized with K₃Fe(CN)₆ to the corresponding phthalazines.     

Tubotaiwin-N-oxid aus der Wurzelrinde von Conopharyngia johnstoni Stapf. 148. Mitteilung über Alkaloide

From the root bark of Conopharyngia johnstonii Stapf (Apocynaceae) the hitherto unknown tubotaiwine-N-oxide ( 2 ) together with tubotaiwine ( 1 ) were isolated and characterized.