R. H. Martin

Thermal racemisation of hepta-, octa-, and nonahelicene : Kinetic results, reaction path and experimental proofs that the racemisation of hexa- and heptahelicene does not involve an intramolecular double diels-alder reaction

Abstract Kinetic results for the thermal racemisation in solution of hepta-, octa- and nonahelicene have been collected. A “conformational pathway” is suggested for these racemisations.

Resolution and optical properties ([α]max, ord and cd) of hepta-, octa- and nonahelicene

Abstract Hexa-, hepta-, octa- and nonahelicene give conglomerates from chloroform and 1,2-dichloroethane solutions. The partially resolved helicenes thus obtained are purified by repeated crystallisations, out of equilibnim conditions. The UV, ORD and CD curves of the pure enantiomers are shown in Figs 1, 2 and 3.

13C-NMR spectroscopy: Isotope shifts and couplings in mono- and dideuteriated polycyclic aromatic hydrocarbons—XIX☆

Abstract The deuterium isotope upfield shifts and couplings ( J 13 Cα-D and J 13 Cγ-C-C-D ) observed in the 13 C-NMR spectra (22·63 MHz) of naphthalene-1-d, naphthalene-2-d, phenanthrene-9-d, benzo[c]phenanthrene-2-d, hexahelicene-7-d and anthracene-9,10-d 2 can be used to assign some of the following 13 C-signals: 13 C α -D, 13 Cβ-C-D ortho , 13 C γ -C-C-D meta ( 3 J t ) and 13 C γ -C-C-D peri ( 3 J t ). These isotope effects are particularly useful for the assignment of the signals of the carbon atoms common to two rings (quaternary carbon atoms, C Q ). The study of anthracene-9, 10-d 2 has yielded results which are at variance with published assignments 2 concerning anthracene itself.

Applications of NMR spectroscopy in the field of polycondensed aromatic systems: IX—Tri and tetracyclic derivatives of chromone, 1-thiochromone, xanthen-9-one, thioxanthen-9-one and related structures

Abstract Ortho and peri effects due to cyclic heteroatoms and (thio)carbonyl functions have been compared in the (1-thio)chromone and (thio)xanthen-9-one series. As a result of this work, the 7H-benzo[c]thioxanthen-7-one structure XVI has been assigned to the benzothioxanthone first isolated by Davis and Smile, 3 and the 12H-benzo[b]thioxanthen-12-one structure XVII has been assigned to a new compound synthesized as part of this study. IR spectroscopy has been used to provide certain supplementary information

Experimental and theoretical study of the induced paramagnetic ring-current in the 4-membered ring of biphenylene and related hydrocarbons

Abstract Ring current intensities and proton chemical shifts have been calculated for a series of condensed aromatic hydrocarbons including biphenylenes. The calculations show that an induced paramagnetic ring current occurs in the 4-membered ring of each of the biphenylenes studied and this effect accounts for the observed spectra. PMR measurements on 1-mono-, 2-mono- and 2,3,6,7-tetra-deuteriated biphenylene prove that the chemical shifts of the 1- and 2-protons are at δCDCl3 6.60 and 6.70 respectively and not vice versa as assumed by previous authors.

Double helicenes: Diphenanthro[4,3-a; 3′,4′-o]picene and benzo[s]diphenanthro[4,3-a; 3′,4′-o]picene

Abstract The synthesis and NMR spectra of the title compounds are described. An X-ray diffraction study, carried out by Dr. J. D. Dunitz (ETH, Zurich), showed that the only product isolated from the photocyclisation of 6 has the dl configuration.

Applications de la spectrographie de résonance magnétique nucléaire (RMN) dans le domaine des dérivés polycycliques à caractère aromatique-XII. Couplages intercycles entre protons aromatiques dans les dérivés du phénanthrène et du benzo[c]-phénanthrène

Abstract Cross-ring coupling between aromatic protons has been observed in substituted phenanthrene and benzo[c]phenanthrene derivatives. It is suggested that the well resolved cross-ring coupling of H 1 in 4-methoxybenzo[c]phenanthrene and 4-aminobenzo[c]phenanthrene involves two protons (H 5 and H 8 ), one of which (H 8 ) is located in a non-adjacent ring (Fig. 2).

Propriétés physico-chimiques de dérívés aromatiques pontés: [2,2], [2,2,2] et [2,2,2,2] metacyclophanes

Abstract [2.2], [2.2.2] and [2.2.2.2] metacylophanes have been obtained by the action of sodium and tetraphenylethylene on meta -dibromoxylylene. Examination of the UV and charge transfer complexes (TCNE) spectra indicates the existence of transannular interaction in these derivatives. Strong absorption bands (1400-400 cm − region) due to the distorsion of the benzene rings appear in the IR spectrum of [2.2]-metacylophane. NMR and mass spectra are also described.

Applications de la spectrographie de resonance magnetique nucleaire (RMN) dans le domaine des derives polycycliques A caractere aromatique—XI: Spectres de 19 derives monosubstitues du benzo[C]phenanthrene

Abstract From the study of a large number of monosubstituted benzo[c]phenanthrene derivatives, the following conclusions can be drawn: 1. When R  OCH 3 , NHCOCH 3 or NH 2 , the position of substitution can be specified by first order analysis of the NMR spectra. In the case of NH 2 , such analyses are nevertheless insufficient to make a choice between position 5 and 6. 2. The distorsion of the benzo[c]phenanthrene ring system has practically no effect on the perturbations induced by a substituent located in a non-hindered position.

Applications of NMR spectroscopy in the field of polycyclic aromatic compounds—VIII : Biphenylene and benzobiphenylene derivatives

Abstract NMR spectra of benzo [b] biphenylene and of substituted biphenylenes, benzo [a] biphenylenes and benzo [b] biphenylenes have been recorded at 60 Mc. These spectra fully confirm the structures previously assigned to the twelve derivatives examined in this work. The expected spectraum of benzo [a] biphenylene is deduced from the spectra of its substituted derivatives. The main results are summarized.