Nitration of octafluoro[2.2]paracyclophane (OFP) provides an entry into the synthesis of a series of 11 monosubstituted OFPs, including the nitro, amino, chloro, bromo, iodo, hydroxy, and trifluoromethyl compounds. The NMR, mass spectrometric, and UV spectral properties of all of these derivatives are presented and discussed, and they are compared with those of its hydrocarbon analogue, [2.2]paracyclophane.

Synthetic methods for introduction of two substituents into the rings of octafluoroparacyclophane are presented. Nitration gives three isomers with nitro substituents on different rings: pseudo-ortho, pseudo-meta, and pseudo-para, in equal amounts. These dinitro compounds are shown to be precursors of a variety of other disubstituted OFP derivatives. Methods of characterization of isomeric disubstituted OFPs are extensively discussed, and the 1H and 19F NMR spectra of these derivatives are analyzed explicitly.

A novel synthesis of octafluoro[2.2]paracyclophane (AF4), one that remarkably does not require the use of high dilution methodology, is presented. Using this unprecedented methodology, AF4 is produced in 60% yield in a reaction of Zn with 0.35 M p-bis(chlorodifluoromethyl)benzene in DMA at 100 degrees C. The process comprises a convenient, inexpensive, and highly scaleable preparation of AF4 for both research and commercial purposes.

Direct routes for the synthesis of pentakis(trifluoromethy1)cyclopentadienide salts, hexakis(trifluoromethy1)cyclopentadiene and 5H-pentakis(trifluoromethyl)cyclopentadiene are described.

Abstract:The well-established synthesis of heptafluorobut-2-ene 2 from hexachlorobutadiene 1 and potassium fluoride has been further investigated, and novel dienes 3 and a triene 4 have been observed. Remarkably, the potassium salt of pentakis(trifluoromethyl)cyclopentadienide 7 has been isolated from this system. Salt 7 has also been obtained directly from 2. Cyclopentadiene 6 has been isolated from salt 7 by distillation from sulphuric acid. Bi-and tri-cyclic analogues of 7 have also been obtained, i.e., 9 and 10, by reaction of 2 with perfluorocyclopentene.Key words: heptafluorobut-2-ene, pentakis(trifluoromethyl)cyclopentadienide 5H-pentakis(trifluoromethyl)cyclopentadiene.RCsumC : On a CtudiC 2 nouveau la synthbse bien connue de l'heptafluorobut-2-kne 2 2 partir de 1'hexachlorobutadibne 1 et du fluorure de potassium; on a observC la formation de nouveaux dibnes 3 et d'un trikne 4. D'une f a~o n remarquable, on a isolC de ce systbme le pentakis(trifluoromCthyl)cyclopentadiCnure de potassium 7. Par distillation du sel7 en prksence d'acide sulfurique, on a isolC le cyclopentadikne 6 2 partir du sel7. La rkaction du composC 2 avec le perfluorocyclopentkne a permis aussi d'obtenir les analogues bi-9 et tricycliques 10 du composC 7. IMots clPs : heptafluorobut-2-ene, pentakis(trifluoromCthyl)cyclopentadiCnure, 5H-pentakis(trifluoromethyl)cyclopentadikne. [Traduit par la redaction]There is a wide interest in methodology for the introduction of trifluoromethyl and other perfluoroalkyl groups into organic compounds (2), and we are concerned with the alkene (2)-2H-1 heptafluorobut-2-ene 2 as a potential "building block.' for this ' purpose. This F-alkene is especially significant because it can ' be obtained directly from hexachloro-l,3-butadiene 1, by simple displacement using potassium fluoride in an aprotic solvent. This synthesis was described in 1963 by Maynard (3), from the du Pont Co., and has subsequently been used by other workers, including this laboratory (4). However, in recent further investigation of this reaction, we have discovered some remarkable new products.The overall procedure involves heating hexachloro-1,3-butadiene 1 with anhydrous potassium fluoride in an aprotic solvent; Maynard (3) described N-methyl-2-pyrrolidinone and we have found that sulpholan is very satisfactory (4). The products vary significantly with reaction conditions, and we have now identified and separated from 2 two interesting new fluorinated dienes 3a and 3b, and even a triene 4. These compounds were separated by fractional distillation and the stereoReceived November 14, 1995. R.D.Chambers@durham.ac.uk chemistry of the major diene isomer 3a follows from I9F NMR coupling constant data, since it is known that 5~( c i s -~~3 ,~~3 values are greater than 10 Hz, 5~( t r a n s -~~3 ,~~3 ) values are typically less than 2 Hz, and 4~( t r a n s -~~3 ,~) coupling constants are less than for 4~( c i s -~~3 ,~) ( 3 , as shown in Fig. 1. In contrast, we were unable to deduce the structure of the minor isomer 3b (see experimental sect...