Electron impact and chemical ionization mass spectra of bis(methoxycarbonyl) [2.2](2,5)pyridinophanes. Formation of quinolizinium ions under electron impact

For four isomeric bis(methoxycarbonyl)[2.2](2,5)pyridinophanes differing only in the mutual orientation of the two nicotinic ester units, electron impact mass spectra were measured. The fragmentations observed distinguish surprisingly well between the isomers, depending on the transannular substitution pattern. Of special interest is that for one isomer the otherwise unimportant ion at m/z 298 is found as base peak. This ion is formed by expulsion of HCN from the molecular ion, transannular cycloaddition and aromatization to a stable quinolizinium ion. Fragmentation pathways of the isomers are compared, and chemical ionization and negative ion chemical ionization mass spectra are discussed.     

Three isomeric bis(methoxycarbonyl)[2.2]paracyclophanes

The title isomers 4,16‐ (pseudo‐ortho), 4,15‐ (pseudo‐gem) and 4,12‐bis­(methoxy­carbonyl)[2.2]­para­cyclo­phane (pseudo‐para), C₂₀H₂₀O₄, all show the typical structural features of [2.2]­para­cyclo­phanes (flattened boat conformation of the rings, lengthened single bonds in the bridges and narrow ring angles at the bridgehead atoms). The 4,12‐isomer displays crystallographic inversion symmetry. The carbonyl groups adopt a conformation in which they are directed away from the ring systems towards the nearest bridge; the corresponding angle at the ring substituent atom is widened. Crystal packing involves C—H?π interactions for the 4,15‐isomer and weak C—H?O hydrogen bonds for the other two isomers.     

Cyclophanes—VII : Conformations of [2.2](2,5)furanoparacyclophane,[2.2](2,5)furano(1,4)naphthalenophane and [2.2](2,5)furano(9,10)anthracenophane. perpendicularity of aromatic moieties

Variable temperature NMR spectroscopy was used to study the conformational behavior of [2.2](2,5)furanoparacyclophane (1), [2.2](2,5)furano(1,4)naphthalenophane (2) and [2.2](2,5)furano(9,10)anthracenophane (3). While the method was useful in studying 1, it was not adequate for 2 and 3. Variable temperature UV absorption and fluorescence emission studies provided information on the conformations of 2 and 3. The UV absorption and emission spectra of 1 were blue-shifted relative to their ambient temperature spectra. Those of 2 were not shifted at all and those for 3 were red-shifted. The data is consistent with an anti-orientation of the aromatic rings in 2 both at ambient and low temperture. The aromatic rings in 3 are perpendicular to one another at low temperature and probably at room temperature as well. Exiplex bands were absent in the room temperature emission spectra of 1, 2 and 3 as well as the low temperature spectra of 2 and 3. An exciplex band was observed in the low temperature emission spectrum of 1.     

Synthesis and structural study of [2.n](2,5)pyridinophanes

[2.n](2,5)Pyridinophanes possessing a cyclobutane ring and dioxaoligomethylene chain as tethers were efficiently prepared by intramolecular [2 + 2] photocycloaddition of vinylpyridine derivatives using a 400-W high-pressure mercury lamp through a Pyrex filter. They were of cis-configuration with respect to the cyclobutane ring, which was proved by the specific methine proton signals at δ 3.95-4.14. If the dioxaoligomethylene chain is short, the reaction affords only two exo,syn- and anti-isomers among three possible ones. On the other hand, if the chain is long enough, it gives three possible isomers interconverting at equilibrium. It is concluded that [2.n](2,5)pyridinophanes are rigid if n=4, 5 but flexible if n?6.     

[2.2](2,5)Pyrazinophanes: Synthesis and Molecular Structure

The pseudoortho (4a) and the pseudogeminal [2.2](2,5)pyrazinophane (_4b) have been synthesized via 1,6-Hofmann elimination of [(5-methyl-2-pyrazinyl)methyl]trimethylammonium hydroxide (2b) and dimerization of the generated 2,5-dihydro-2,5-bis(methylene)pyrazine (3). The molecular structures of both isomers, 4a and 4b were determined by X-ray analysis.     

Untersuchungen zur Hydrolyse von 3,5,10,12-Tetramethoxy-3,5,10,12-tetrahydro-[2.2](2,5)furanophan

Hydrolysis of2 in 0.005M-H₂SO₄ yields3, which forms two stereomeric bicyclic compounds4 and5 by ketol addition. In 0,5M-H₂SO₄ 2 yields the furanophane12, which in turn yields the diasteromeric tetracycles9 and10, which on hydrolysis yield theas-indacene11. The structures and configurations of the new compounds were proved by chemical and spectroscopic methods.

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Teilweise aus der Dissertation vonE. Zeisl, Univ. Wien, 1976.     

Transannular interactions insyn- andanti- [2.2](1,4) napthalenophanes andsyn- andanti- [2.2](1,4) anthracenophanes

The UV spectra of the title compounds were interpreted as a result ofPPP-CI-1 calculations of excitation energies and oscillator strengths for the singlet—singlet transitions. A good agreement of the theoretical transitions with the experimental spectrum was found. A strong transannular effect was characteristic for thesyn isomers, the effect decreased in the order:syn-ring anthracenophane,syn-ring naphtalenophane,anti-ring naphthalenophane,anti-ring anthracenophane. Also the influence of a pseudo-substituent effect was found and discussed.     

Conformation of dithia[3.3]- and [2.2] azuleno(2,6)pyridinophanes

Four azuleno(2,6)pyridinophanes (1–4) were synthesized and their conformations were found by NMR spectroscopy to be very similar to those of the corresponding azulenometacyclophanes. A transverse conformational change was observed for [2.2](5,7)azuleno(2,6)pyridinophane.     

[2.2](2,6)Biphenylenophane and [2](2,6)Biphenyleno[2](2,6)naphthalenophane

Two cyclophanes, [2.2](2,6)biphenylenophane and [2](2,6)biphenyleno[2](2,6)naphthalenophane, were prepared.     

Phenylbismuth Bis(2,5-dimethylbenzenesulfonate): Structure and properties

Phenylbismuth bis(2,5-dimethylbenzenesulfonate) (I), a coordination polymer in which a bismuth atom has a distorted square pyramidal coordination to an axial carbon atom (Bi-C, 2.247(5) Å) and basal oxygen atoms (Bi-O, 2.390(9)–2.403(10) Å), has been synthesized by the reaction between triphenylbismuth and 2,5-dimethylbenzenesulfonic acid (1: 2 mol/mol) in toluene and structurally characterized. Pentaphenylbismuth and pentaphenylantimony phenylate compound I to triphenylbismuth.