Nature of the chemical bonds in HCN and C2N2

The function (M), which measures the effect of the bond formation on the electron density distribution, has been calculated for HCN and C₂N₂. The charge build up in the CN bonds is found to be quite the same in both molecules, which indicates that the outer bonds of C₂N₂ are practically unaffected by conjugation.

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Zusammenfassung Die Funktion (M), ein Maß für die Änderung der Elektronendichteverteilung durch Bildung von Bindungen, wurde für HCN und C₂N₂ berechnet. Danach ist die Ladungsanhäufung in den CN-Bindungen für beide Moleküle praktisch gleich, was darauf hinweist, daß die äußeren Bindungen im C₂N₂ durch die Konjugation kaum verändert werden.

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Résumé La fonction (M), qui mesure l'effet de la formation des liaisons sur la distribution de la densité électronique, a été calculée pour HCN et C₂N₂. D'après les calculs, l'accumulation de charge dans les liaisons CN est pratiquement la même dans les deux molécules, ce qui indique que les liaisons extérieures de C₂N₂ ne sont en fait pas affectées par la conjugaison.

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We are thankful to Miss Cl. Litt for programming the calculation of the function and to Mrs. M. Henseval for drawing the density contours.     

Sur les dérivés de la fluorénone VI Les acides bromo-3-fluorénonecarboxylique-2 et bromo-2-fluorénonecarboxylique-3 et la bromo-3-méthyl-4-fluorénone

Starting from 2-amino-3-bromo-9-oxofluorene and from 3-methylfluorene respectively the preparation of 3-bromo-9-oxofluorene-2-carboxylic acid and of 2-bromo-9-oxofluorene-3-carboxylic acid is described. A synthesis of 3-bromo-4-methyl-9-oxofluorene is also given.     

Preparation of Neutral Ionophores for Alkali and Alkaline Earth Metal Cations and their application in ion selective membrane electrodes

The preparation of a series of non-cyclic, uncharged ligands able to selectively complex alkali and alkaline earth metal cations is described. These molecules are designed to be used as carriers for cations through membranes. Some of the compounds show high Ca²⁺ and Na⁺ selectivity, respectively, in liquid membrane electrodes.     

Highly efficient transfer of chirality from macrocyclic conformation in the tandem oxy-Cope/Claisen/ene reaction

We report three highly stereoselective pericyclic reactions occurring in cascade leading to the synthesis of Decalins skeletons possessing two contiguous quaternary centers. The tandem reaction is triggered by an oxy-Cope rearrangement to create in situ a 10-membered ring enol ether macrocyle 6, which immediately rearranges via a Claisen [3,3] shift to the corresponding E-cyclodec-6-en-1-one 7. The latter spontaneously cyclizes via a transannular ene reaction to produce Decalin 5. Analysis of the mechanism with respect to the origin of the high diastereoselectivity of the tandem oxy-Cope/Claisen/ene reaction is presented.     

Fluorénacènes et fluorénaphènes Synthèses dans la série des indéno-fluorènes,XV [1] Méthyl-5-dihydro-10, 12-indéno [2, 1-b]fluorène

Starting from α-methylchalcone and diethyl ketone the title compound, II, has been synthesized in 6 steps (overall yield 26%). As an intermediate compound the gold yellow 10, 12-dioxoderivative of II was also obtained.     

Synthèses dans ka série des bis-indéno-fluorènes II. Le dihydro-10,15-5H-bis-indéno [1, 2-a;2′,1′-i] fluorène

The biangular bis-indeno-fluorene 10,15-dihydro-5H-diindeno [l, 2-a; 2′, 1′-i]-fluorene (XII) has been synthesised in 6 steps starting from 1-(o-carboxyphenyl)-fluorenone (overall yield 21%). As an intermediate the 5,10,15-trioxoderivative of XII and, accessorily, its 5,10-dioxoderivative were also obtained.     

Reactivite des carbanions benzyliques : VIII. Etude de la structure d'alkyl-9 lithio-10 dihydro-9,10 anthracenes par rmn du proton et spectrometrie d'absorption electronique; influence du substituant,du solvant et de la temperature

The structure of the 9,10-dihydroanthracenyl anion and of a series of 9-alkyl-10-lithio-9-10-dihydroanthracenes (9-R-10-LiDHA, I–V where R = H, Me, Et, i-Pr, t-Bu) was studied in solution by electronic absortion spectrometry and proton magnetic resonance. Our electronic absorption results, in addition to those of other authors, show that the contact ion pairs (c.i.p.) have an absorption at λ_max}- 400 nm (I–III) and 415 nm (V) whereas the loose ion pairs (l.i.p.) absorb at λmax}- 450 nm (I–V). In the NMR the chemical shift of the proton para with respect to the carbanionic center was examined as a function of solvent (THF, THF/HMPA, and in some cases ether or pure HMPA) and temperature (+20 to ?40°C). The para proton is shielded significantly with regard to the aromatic protons of the hydrocarbon (Δδ(H_para) ca. 1–1.7 ppm). The weakest shielding was observed in ether, in agreement with the existence of c.i.p. The largest shielding (THF/HMPA or pure HMPA) is in connection with the presence of l.i.p. where the negative charge is less localised at position 10. Moreover, in the same solvent, and at the same temperature, Δδ(H_para) was observed to increase with the substituent bulk, up to the point that there are only l.i.p. present. As found previously (namely for the fluorenyl anion) the l.i.p./c.i.p. ratio increases when temperature decreases. The results of this structural study allow to rationalize the protonation stereochemistry of 9-alkyl-10-lithio-9,10-dihydroanthracenes in the above-mentioned solvents.     

Hydrogen bond directed synthesis of pyridazine and naphthyridine containing macrocycles

This work describes a high-yielding, one-step synthesis of pyrizadine and naphthyridine containing macrocycles directed by intramolecular H-bonding.