Medium-Sized Cyclophanes. IV. The Halogenation Reactions of [2.2]Metacyclophane

Abstract

It has been postulated that, with proper control and choice of reaction conditions, the halogenation reactions of [2.2]metacyclophane might be directed in either of two ways: (A) the addition-oxidation path or (B) the addition-elimination path. An attempted iodination (iodine-silver perchlorate or iodine chloride) or bromination (bromine-iron catalyst) of [2.2]-metacyclophane resulted in the formation of 4, 5, 9, 10-tetrahydropyrene according to the path B reaction. On the other hand, iodination reaction in the presence of nitric acid has been shown to afford 2-iodo-4, 5, 9, 10-tetrahydropyrene, after path A. Both the reactions have been explained by assuming a common intermediate, which is formed by the attack of the halogenonium ion on one ring, accompanied by a simultaneous transannular attack of the generated phenonium ion on the second ring.

Cyclophanes containing large polycyclic aromatic hydrocarbons

“…The syntheses highlight a common tactic for the construction of pyrene derivatives, i.e. the conversion of a [2.2]metacyclophane into a comparatively soluble 4,5,9,10-tetrahydropyrenophane 23 followed by dehydrogenation. For example, treatment of either conformer (u,u or u,d) of the layered [2.2]metacyclophane 5 with pyridinium perbromide afforded tetrahydropyrenophane 6, which was then aromatized using DDQ (or NBS) to give 7.…”

Medium-sized cyclophanes. Part 31. Synthesis and electrophilic substitution of 8-substituted [2]metacyclo[2](1,3)pyrenophanes

“…Sat0 et aZ. 44 have reported that the reaction of 8,16-unsubstituted [2.2]MCP with bromine in the presence of iron powder affords the corresponding tetrahydropyrene via an addition4imination mechanism [equation (l)].…”

Synthesis of pentasubstituted 3-hydroxy-1,2-dioxolanes

“…Five-membered cyclic peroxides are of synthetic and mechanistic importance. [1][2][3] Several examples of 3hydroxy-l,2-dioxolanes (hemiperketals) and related ring systems have been found as natural products.2,4 Synthetic (1) Bloodworth, A. J.; Eggelte, H. J. In Singlet 02; Primer, A., Ed.…”

“…Sato and his co-workers2 have reported that bromination of 8,16-unsubstituted [2.2]metacyclophane (MCP = metacyclophane) with bromine in the presence of Fe powder afforded the corresponding tetrahydropyrene via an addition-elimination mechanism.3 456"8 Recently, we reported9 that in similar bromination reactions of 8,16-dimethyl[2.2]MCP (la), the isomerization and transannular cyclization product, 2,7-dimethyll,3,6,8-tetrabromo-4,5,9,10-tetrahydropyrene (2), was obtained due to the release of the strain in the molecule. This novel isomerization and transannular cyclization reaction might be attributed to the methyl groups at the 8,16positions, which increase the strain in the molecule in comparison with the 8,16-unsubstituted [2.2]MCPs.…”