Remarkable efficiency of the aryne chemistry of (dehydro)octafluoro[2.2]paracyclophane when using the Cadogan method.

Generation of the aryne, (dehydro)octafluoro[2.2]paracyclophane, from its acetamide derivative utilizing the Cadogan method led to remarkable results with respect to Diels-Alder and ene reactivity. A comparison was made between this new and virtually unused method and our earlier reported results using Cram methodology (reaction of aryl iodide with potassium tert-butoxide).

The cycloaddition strategy for the synthesis of natural products containing carbocyclic seven-membered rings.

Highly substituted carbocyclic seven-membered rings are frequently found in natural products and their synthesis represents a significant challenge to the synthetic chemist. Direct intramolecular cyclization of these systems often proves difficult and this fact has catalyzed the development of a variety of strategies based on a convergent intermolecular cycloaddition strategy. This concept article discusses the major cycloaddition approaches utilized to access these types of structures and primarily focuses on examples employed in the synthesis of natural products.

A highly pyramidalized cage alkene formed via the double Diels-Alder cycloaddition of syn-4,5,13,14-bis(dehydro)octafluoroparacyclophane to anthracene.

[reaction: see text] A double Diels-Alder reaction of the formal syn-bis(dehydro)octafluoroparacyclophane with anthracene leads to formation of a novel cage compound that contains a highly pyramidal double bond. The measures of pyramidality of this double bond constitute what appear to be the highest combined values of psi and phi (34.3 degrees and 33.

Bridged synthons from tetrabromocyclopropene: studies on the rearrangement of the primary Diels-Alder adduct with 2,5-dimethylfuran.

The reaction of tetrabromocyclopropene and furan leads directly to 8-oxabicyclo[3.2.1]octadiene derivatives.

Bicyclo[3.2.1]octane synthons from cyclopropenes: functionalization of cycloadducts by nucleophilic additions.

It has been known for several decades that a highly functionalized family of tetrahalobicyclo[3.2.1]octadienes are readily available through the cycloaddition of furan or cyclopentadiene with either tetrachloro- or tetrabromocyclopropene.

4,5-dehydro- and 4,5,15,16-bis(dehydro)octafluoro[2.2]paracyclophanes: facile generation and extraordinary Diels-Alder reactivity.

Dehydroiodination of 4-iodo- and 4,15-diiodo-1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane by treatment with KO(t)Bu in the presence of benzene, naphthalene, anthracene, and [2.2]paracyclophane affords each of the corresponding Diels-Alder mono- and bis-cycloadducts derived from the presumed aryne intermediates in high yield.

EPR support for the ketyl radical-anion "triggered" [3,3]-sigmatropic rearrangement.

New physical evidence to support a ketyl radical-anion mechanism for the [3,3]-sigmatropic rearrangement is presented. With use of EPR spectroscopy, spectra are observed that can be attributed to 8, an acyl radical-anion species resulting from a [3,3]-rearrangement; this also functions as a key intermediate in the process. The spectrum of an additional paramagnetic species resulting from further addition of tin-centered radicals to the reaction product was also observed.

Silver-promoted reactions of bicyclo[3.2.1]octadiene derivatives.

[reaction: see text] Highly substituted bicyclo[3.2.1]octadiene building blocks are easily prepared from tetrachloro- or tetrabromocyclopropene through reaction with cyclic dienes.

Computational discovery of a novel automerization process for 1-fluorocyclopropene.

[reaction: see text] Both DFT and CCSD and CCSD(T) computational methods indicate that 1-fluorocyclopropene can undergo an unprecedented "electrocyclic" automerization process involving a full 180 degrees rotation of its methylene group, without the formation of an intermediate carbene or diradical.