Johannes C. Jochims

Nuclear magnetic resonance of organic free radicals

The conditions under which N.M.R. spectra of organic free radicals can be observed are discussed. The N.M.R. spectra of several radicals are shown and compared with the E.S.R. spectra of the same radicals. The N.M.R. spectra are particularly useful to determine small coupling constants which are below the limit of resolvability of E.S.R. and ENDOR. Futhermore, N.M.R. renders the sign as well as the magnitude of the interaction between the unpaired electron and the nucleus investigated; it can contribute to the understanding of the mechanism of this interaction.

[3+2]-cycloadditions of 1-Aza-2-azoniaallene cations to multiple bonds

Abstract Hydrazones of ketones 1, are transformed into 1-chloroalkylazo compounds, 2, which react with Lewis acids to give transient 1-aza-2-azoniaallene salts, 3. The cations 3 react with with acetylenes, olefins, isocyanates, carbodiimides, and nitriles under [3+2]-cycloadditions. The cycloadducts undergo consecutive reactions, e.g. [1,2]-shifts of alkyl groups.

On the reaction of 1,3-diaza-2-azoniaallene salts with 1,3-butadienes and cumulenes

Abstract 1,3-Disubstituted triazenes 3 are oxidized with tert-butyl hypochlorite to N-chlorotriazenes 4, which at low temperatures with antimony pentachloride afford 1,3-diaza-2-azoniaallene salts 5 as reactive intermediates. Cations 5 undergo cycloadditions to one or both double bonds of 1,3-butadienes to furnish 4,5-dihydro-1H-1,2,3-triazolium salts (6a-k) (1,3-dipolar cycloaddition with inverse electron demand). With an allene, a butatriene, and a pentatetraene the 4,5-dihydro-1H-1,2,3-triazolium salts 6l-n were obtained. Some of the products undergo consecutive reactions to 1,2,3-triazolium salts (8a,b). The constitutions of 6n and 8b were secured by X-ray structural analyses. 4,5-Dihydro-1H-1,2,3-triazolium salts (6) and 1H-1,2,3-triazolium salts (8) are aza analogues of Arduengos nucleophilic carbenes (imidazolidine-2-ylidenes, imidazole-2-ylidenes).

Isocyanato- und Isothiocyanato-Derivate des D-Glucosamins

Zusammenfassung Aus 1,3,4,6-Tetraacetyl-β- d -glucosamin·HCl 1 erhielten wir mit Phosgen bzw. Thiophosgen in 90-proz. Ausbeute 1,3,4,6-Tetraacetyl-2-desoxy-2-isocyanato-β- d -glucose (IIa) und 1,3,4,6-Tetraacetyl-2-desoxy-2-isothiocyanato-β- d -glucose (IIb). Die Verbindungen (IIa und IIb) wurden in hohen Ausbeuten zu Urethanen, Harnstoffen, Semicarbaziden und N-Hydroxy-harnstoffen umgesetzt.

nido- und closo-Cluster als Halbsandwich- und Tripeldeckerkomplexe: ein einfaches MO-Modell zur Deutung des Redoxverhaltens von Clustern

Abstract The halfsandwich-type compounds η4-[R (CO)3]Fe(CO)3, (X = Se, Te) 1a, 1b (type A), may be stacked to the tripeldecker-type compounds μ2-η4-[R (CO)3]Fe2(CO)5, 2a (X = Se), 2b (X = Te) (X-ray analysis) (type B). The relation between the compounds 1 and 2 is the same as the one between the nido pentagonal pyramidal clusters η5-[R (CO)3]Fe(CO)3, 3 (type C) and their closo derivatives μ2-η5-[R , 4 (type D). The analysis of a specific dynamic behaviour of compounds 3 is reported. In addition a model is proposed, which explains the observed pairwise relation in the redox potentials of structurally related nido and closo compounds in a simple manner.

The reaction of 2,4,6-tris(trimethylsiloxy)-1,3,5-triazine with chlorocarbenium ions: a new access to 1-oxa-3-azabutatrienium and 2-azaallenium salts

Abstract Chlorocarbenium salts 2a - d of the Vilsmeier-Arnold type react with the silylated isocyanuric acid 3 to give 1-oxa-3-azabutatrienium salts 1 under mild conditions. From reactions of diarylchloromethenium salts 2h - 1 with 3 and ketones or tertiary carboxamides high yields of 2-azaallenium salts 9 were obtained. A few chloro substituted 2-azaallenium salts 5 were prepared from 1b and carbonyl compounds. The mechanisms of the new reactions are discussed.

3,4-DIHYDROQUINOLINIUM SALTS : PREPARATION BY REACTION OF N-ARYLNITRILIUM SALTS WITH ALKENES

N-Arylnitrilium salts 1 react with nucleophilic alkenes 2 to afford 3,4-dihydroquinolinium salts 3, which can be transformed into the free bases with aqueous sodium hydroxide. Dehydrogenation of the 3,4-dihydroquinolinium salts 3 with 2,3-dichloro-5,6-dicyano-p-benzoquinone furnishes quinolinium salts 7. If the intermediate carbenium ion A formed by electrophilic attack of 1 on the alkene 2 is conjugatively or hyperconjugatively stabilized, instead of 3,4-dihydroquinolinium salts 3 iminium salts 4 resulting from a Houben-Hoesch reaction, or iminium salts 5 arising from a formal ene reaction are formed. For the 3,4-dihydorquinolinium salt 3ac X-ray structural analysis has been carried out.

The reaction of 2-azaallenium salts with carbodiimides and tert-butyl isocyanide

Abstract 2-Azaallenium salts 1 react with diisopropyl carbodiimide to afford the formal dihydro-1,3-diazetium salts 5 . The structure of 5c has been confirmed by an X-ray diffraction analysis. With the carbodiimide 2e the tetraphenyl-2-azaallenium salt 1a reacts to give the guanidinium compound 6 .The diazetium salts 5 react with further carbodiimide to afford the formal 2-azaallenium salts 11 . With tert-butyl isocyanide the 2-azaallenium salts 1 undergo an Ugi reaction to yield the nitriles 14 .

Reduktion von Ketoximen mit Zinkstaub in ammoniakalischer Lösung

Ketoxime lassen sich oft besser in konzentriert ammoniakal. als in saurer Losung durch Zinkstaub zu den primaren Aminen reduzieren. Beschrieben werden ergiebige Synthesen von 9-Amino-fluoren, Benzhydrylamin, [α-Naphthyl-phenyl-methyl]-amin, Alanin u. a.

N-ACYLIMINIUM SALTS FROM THE REACTION OF NITRILIUM SALTS WITH ALDEHYDES

Abstract The nitrilium hexachloroantimonates 2a,d,g,p react with aromatic aldehydes to give isolable N-acyliminium hexachloroantimonates 10a-m. The N-aroyliminium salts (10g-m) and acyliminium salts with an aliphatic N-acyl group (10a-f) are of remarkably different stability. Contrary to the N-aroyliminium salts, compounds 10a-f are unstable in solution, e. g. react immediately with acetonitrile. With excess of aldehyde 10n,o give insertion products of the probable structures 12a,b. For 10b,f X-ray structural analyses have been carried out. The N-acylcyanamidium hexachloroantimonate 2p reacts with aldehydes to give new classes of cyclic N-acyliminium salts 13a-f, and 14f, respectively.