P. Ashkenazi

Propellanes—XXXVI : Reactions of bridged [10]annulenes with 4-substituted-1,2,4-triazoline-3,5-diones

Abstract 1,6-Methano-, 1,6-oxa-, 1,6-imino- and 1,6-methylimino[10]annulene as well as several derivatives of the first-named compound react with 4-substituted-1,2,4-triazoline 3,5 diones to give mono - and/or bis -adducts. Attack apparently occurs from the side anti - to the bridging atom. Mass spectral results are reported for certain mixed di-adducts.

Determination of synthetic food colours by means of a novel sample preparation system

Abstract A novel self-contained system, dynamic column solid-phase extraction (DC-SPE), for the facile extraction and concentration of five widely used synthetic food dyes is described. The determination of the DC-SPE-extracted dyes in both standard solutions and commercial products was done by rapid square-wave voltammetry and by liquid chromatography in the concentration ranges 1.0 × 10−6−2.0 × 10−5 M and 1.0 × 10−5−1.0 × 10−4 M, respectively. The method of standard additions was used to determine recoveries for several commercial products.

Formation of nitroxide radicals in the α-ferrocenylcarbonium ion-nitrosobenzene system

Abstract The nitroxide radicals produced by treatment of α-ferrocenylcarbonium ions with nitrosobenzene have been studied and characterized by ESR spectroscopy and by chemical transformation to ferrocenyl-containing substituted anilines. Possible mechanisms for the formation of these nitroxides are discussed, and their relevance to structural problems of the α-ferrocenylcarbonium ions considered.

Propellanes—XLIII: Inhibition of secondary orbital control in diels-alder reactions of certain propellanes with 4-substituted-1,2,4-triazoline-3,5-diones1

Abstract A number of propellane substrates were prepared with special structural features, such that attack by dienophiles would be (a) from below—due to repulsive interactions, both electronic and steric, or (b) if the electronic influence from above was less efficient, than the attack would be from both directions. The predicted course of all the reactions has been realised experimentally.

Reaction of bicyclic dienes with 4-substituted-1,2,4-triazoline-3,5-diones

Abstract Reaction of 1,2-dihydrophthalic anhydride and several of its imide derivatives, 1,2-dihydrophthalide and 1,2-dihydrophthalan with N-methyl- and N-phenyl-1,2,4-triazoline-3,5-dione affords two configurational families of adducts through attack from both possible directions. Major attack in the first three cases occurs mainly syn - to the hetero-ring but in the two latter cases anti - to it. These results may be explained by invoking stabilization of the transition state in the former cases through secondary orbital overlap and by simple steric effects in the latter.

Propellanes-XLV: Symmetry correlation of diels-alder adducts of tetraenic propellanes with their nmr spectra

Abstract Propellane derivatives having different symmetry have been prepared and their NMR spectra measured.

Propellanes-li. diels-alder reactions of 12-methyl-12-aza [4.4.3] propella-2,4,7,9-tetraene with nitroso-aromatic dienophiles

Abstract Regiospecificity in attack of the title- bis -diene by aromatic nitroso compounds as dienophilic components is lower than that of other dienophiles of the triazolinedione type.

Propellanes—XLIX : Relative diels-alder reaction of an unsubstituted and a substituted diene system in propellanes and 1,6-methano[10]annulenes1

Abstract The relative reactivity of an unsubstituted cyclohexadiene ring and a substituted cyclohexadiene ring within a propellane system or a 1,6-methano[10]annulene system has been studied.

Propellanes : XCVI. Unambiguous chemical ionization mass spectral assignment of configurations to the diols obtained by reduction of [n.3.3]propellanediones and hplc purification

Abstract i-Butane chemical ionization mass spectrometry (CIMS) enables unambiguous configurational assignment of anti,anti[n.3.3]propellane diols which give rise to abundant [M+H] + ions in contrast to the syn,syn- and syn,anti-isomers. The syn,syn- and syn,anti-isomers may be differentiated by the relative abundance of the [ M+ C 4 H 9 -2H 2 0] + ions under i-C 4 H 9 -CIMS conditions.

Propellanes. Part lxxxvi: The structures of the three isomeric [4.3.3]propellane-8,11-diols

Abstract The structures of the title diols have been determined by NMR and X-ray crystallography.