Model calculations of the interaction of two parallel antiaromatic 4n pi-electron systems.

The nature of the interaction between decks of a pentalene dimer and an s-indacene dimer has been studied by semi-empirical MNDO/1 and MINDO/3 calculations for distances between decks of from 5 A to 2 A. In contradiction to qualitative predictions from a frontier orbital analysis, it is found that the 4n-4n pi-electron interaction between decks for such dimers is destabilizing for distances exceeding about 2.5 A.

Gas-phase pyrolytic formation and dimerization of benzocyclobutenes: Synthesis of [2(4)](1,2,4,5) cyclophane.

Gas-phase pyrolysis of benzocyclobutenes in a nitrogen stream at 450 degrees C is a convenient efficient method for preparing dibenzocyclooctadienes. Application of this method to benzo[1,2;4,5]dicyclobutene gives [2(4)](1,2,4,5)cyclophane directly. However, under the same reaction conditions, 3,6-dimethylbenzo[1,2;4,5]dicyclobutene gives the open [2.2]orthocyclophane derivative, whose structure has been established by x-ray crystallographic analysis of the corresponding iron complex.

Multilayered iron complexes of [2.2]paracyclophane.

Recent syntheses of ruthenium complexes of [2.2]paracyclophane provided a highly interesting class of compounds, the multilayered transition metal complexes of cyclophanes. The present study discloses that arene-metal exchange procedures with ferrocene derivatives, effected either photochemically or by Lewis acid catalysis, are convenient methods for preparing the analogous multilayered iron complexes of [2.2]paracyclophane.

Benzocyclobutene-o-xylylene valence tautomerization: Oxygen and sulfur analogs.

Gas phase pyrolysis of o-hydroxybenzyl alcohol at 750 degrees C gave o-quinonemethide, which, on isolation, formed a mixture of the corresponding dimer and trimer. However, pyrolysis of o-hydroxy-[1-(4-pentenyl)]benzyl alcohol permitted intramolecular trapping of the intermediate o-quinonemethide, giving 3,4-trimethylene-3,4-dihydrobenzochroman. In contrast, gas phase pyrolysis of o-mercaptobenzyl alcohol readily gave benzo[b]thiete in good yield. The pyrolysis makes this interesting highly strained molecule readily available for study and synthetic application. Preliminary results showed that benzo[b]thiete readily undergoes thermal dimerization, ring-opening reactions with nucleophiles, and a variety of Diels-Alder reactions.

Nuclear magnetic resonance spectroscopy. Ring-current effects on carbon-13 chemical shifts.

A comparison of the (13)C nuclear magnetic resonance chemical shifts of some 15,16-dialkyl-15,16-dihydropyrenes with the corresponding 15,16-dialkyl-2,7,15,16-tetrahydropyrenes provides a measure of the effect of ring current on carbon-13 chemical shifts in which other effects may be expected to be negligibly small. The general conclusion is that the absolute magnitude of the ring-current effect is the same for carbon-13 as for protons when they occupy the same position in space relative to the aromatic pi-electron cloud.