Robert L. Soulen

Perfluoroalkylation of benzene derivatives. An improved synthesis of 1,3-bis(2-hydroxyhexafluoro-2-propyl)-5-(perfluoro-n-alkyl)benzenes

Abstract A three-step high yield synthesis of various 1,3-bis(2-hydroxyhexafluoro- 2-propyl)-5-(perfluoro-n-alkyl)benzenes is described. Significant improvements in the iodination and perfluoro-alkylation of a perfluoroalkylbenzene diol have been achieved. Copper coupling of straight-chain perfluoroalkyl iodides with the iodobenzene derivative in DMSO gave the desired compounds as DMSO complexes in 78–91 percent yield.

Selective reduction of 1-chloro-2-iodoperfluorocycloalkenes with sodium trimethoxyborohydride

Abstract In contrast to other chemical reducing agents, it has been found that sodium trimethoxyborohydride will selectively reduce 1-chloro-2-iodoperfluorocycloalkenes to give good yields of 1-hydro-2-chloroperfluorocycloalkenes. The selective displacement of iodine by hydrogen is discussed in terms of HSAB principles.

Perfluorotetracyclobutacyclo-octatetraene; a planar eight-membered ring system; X-ray crystal structure

The title compound is planar, with a variation of only ±0.036 A in the bond lengths of the eight-membered ring, and gives an enhanced diamagnetism which suggests that there is some double-bond delocalization around the inner ring.

Reactions of 1,2-dichloro-3,3-difluorocyclopropene with potassium thiocyanate and sodium arylsulfinates. Synthesis of 1,2-dithiocyano-3,3-difluorocyclopropene

Abstract The reaction of potassium thiocyanate with 1,2-dichloro-3,3-difluorocyclopropene in DMF leads to the formation of 1,2-dithiocyano- 3,3-difluorocyclopropene. In contrast, the reaction of sodium aryl- sulfinates with 1,2-dichloro-3,3-difluorocyclopropene or tetrachlorocyclopropene gave (E)-1,2-bis(arylsulfonyl)ethene as the only product.

2,2′-dihalo-bis(perfluorocycloalkenes): Part 1. Synthesis

Abstract An improved synthesis of 1-chloro-2-iodo-perfluorocycloalkenes and their copper coupled products, 2,2′-dichloro-bis(perfluorocycloalkenes) is reported. Mixtures of equal molar quantities of different chloroiodoperfluorocycloalkenes react with copper to give predominately the mixed coupled product. For example, 1-chloro-2-iodoperfluorocyclobutene and 1-chloro-2-iodoperfluorocyclopentene react with copper to give 2-chloro-1-[1′-2′-chlorohexafluorocyclopentenyl)]-tetrafluorocyclobutene in 70% yield. The 2,2′-dichloro-bis(perfluorocycloalkenes) react with potassium iodide in DMF to substitute one or both vinylic chlorine atoms by iodine. Copper coupling of 2,2′-diiodo-bis(perfluorocyclopentene) gives the cyclic tetramer perfluorotetracyclopentenocyclo-octatetraene, whereas 2-chloro-2′-iodo-bis(perfluorocyclopentene) and copper gives the linear tetramer 2,2‴-dichlorotetrakis(perfluorocyclopentene).

Reactions of 1,2-dichloro-3,3-difluorocyclopropene with methanolic sodium methoxide

Abstract Slow addition of sodium methoxide in methanol to 1,2-dichloro-3,3-difluorocyclopropene yields initially 1-chloro-2-methoxy-3,3-difluorocyclopropene. Further addition of methoxide in methanol yields preferentially Z 1-chloro-2-fluoro-3,3,3-trimethoxypropene and a small amount of dimethyl malonate. The ortho ester undergoes facile hydrolysis during the reaction and work up to form the acrylate ester, Z methyl 2-fluoro-3-chloroacrylate. A mechanism is suggested to account for the selective isomer formation.

Reaction of methanol with perfluorotetracyclobuta-1,3,5,7-cyclo-octatetraene

Abstract Perfluorotetracyclobuteno-1,3,5,7-cyclooctatetraene (PCOT) is a planar and centrosymmetric molecule which possesses an extraordinary electron affinity due to the planarity of the eight π-electron system and the cumulative electron-withdrawing effects of the 16 fluorine atoms. An improved method for the synthesis of PCOT and the product resulting from the spontaneous reaction of PCOT with excess alcohol is reported. Crystal structures of the methyl ( 1 ) and ethyl ( 2 ) derivatives are described.

Powerful Oxidizing Properties of a Planar [8]Annulene: Tetrakis(perfluorocyclobuta)cyclooctatetraene and Its Radical Anion

The central eight-membered ring of tetrakis(perfluorocyclobuta)cyclooctatetraene (1) is flat both in the crystal and in solution, but tetrakis(perfluorocyclopenta)cyclooctatetraene (2) assumes a tub shape similar to that of parent cyclooctatetraene. This sterically induced structural difference strongly affects the physical properties of compounds 1 and 2. The first and second reduction potentials of 1 in solution, +0.79 and +0.14 V vs. SCE, are considerably more positive than the corresponding values, +0.20 and −0.21 V, of 2. Accordingly, mere contact with Hg metal in N,N-dimethylformamide converts 1 to an unusually stable radical anion 1.− that is persistent in air. The temperature-independent coupling constant, aF=+0.320 mT, of the sixteen equivalent β-19F-nuclei in 1.− is much smaller than the expected value, and the g factor of 1.− is markedly lower than those generally found for structurally related radical anions. In contrast, the characteristic data for 2.−, generated from 2 with K metal in 1,2-dimethoxyethane, comply with the expected data. The coupling constants aF=+0.976 and +0.935 mT, each of eight β-19F-nuclei in 2.−, average +0.951 mT upon raising the temperature from 220 to 260 K. The gas-phase electron affinity of 1, A=3.4±0.2 eV, which was estimated from the reduction potential in solution and from charge-transfer absorption spectra obtained from a series of methylated benzenes and naphthalenes, is among the highest known for neutral organic molecules.

Unusual physical and chemical properties of a planar perfluoroalkylated chclooctatetraene

Abstract Tetrakis(tetrafluorocyclobuta)cyclooctatetraene (PCOT) (C 16 F 16 ) is a unique centrosymmetric molecule with the eight carbon atoms of the inner ring planar. Bond length alternation within the 8 membered ring is only ±0.036 Ā with the longer bond exocyclic to the cyclobutene rings. These structural features will be contrasted with typical perfluoroalkyl substituted benzene and cyclooctatetraene derivatives. PCOT in acetonitrile undergoes rapid and reversible electrochemical reduction at positive 0.79 and 0.14 volts, thus it is one of the most powerful neutral organic oxidants known. Many common organic solvents, ferrocene and elemental mercury are rapidly oxidized by PCOT at room temperature. The absence of a ring flattening barrier (est. 12–22 K cal/ mol) and the 16 F atoms provide theoretical rationale for these observations. The HeI δ photoelectron spectra of PCOT (Ip = 10.3, 11.9 and 12.9 eV) suggests that the molecule retains the planar D 4H symmetry in the gas phase and that the unknown parent hydrocarbon would be air sensitive. Measurements of charge transfer maxima with a variety of donor aromatic hydrocarbons reveal that PCOT may possess the highest electron affinity for any neutral molecule. As expected, PCOT is a powerful dienophile in Diels-Alder reactions.

The complexes of 1,3-bis(2-hydroxyhexafluoro-2-propyl)benzene and 1,4-bis(2-hydroxyhexafluoro-2-propyl)benzene with 1,4-benzodioxane, 1,4-dioxane, dimethyl sulfoxide and pyridine

Abstract Chelating properties of 1,3-bis(2-hydroxyhexafluoro-2-propyl)benzene (1,3-BHPB) and 1,4-bis(2-hydroxyhexafluoro-2-propyl)benzene (1,4-BHPB) have been investigated. We reported previously on the synthesis of dimethyl sulfoxide complexes with 1,3-BHPB and 5-perfluoroalkyl-substituted-1,3-BHPB [1]. Their structure was presented as 1:1 complexes involving chelation of one molecule of Me 2 SO by two hydroxy groups of a molecule of 1,3-BHPB. On the basis of X-ray investigation of 1,3-BHPB-Me 2 SO complex a revised linear structure is assigned to this compound. Both oxygen atoms of 1,4-dioxane and 1,4-benzodioxane are chelated in similar manner by 1,3-BHPB to afford stable complexes with m.p. 65–66° and 44–46°, respectively. The ratio of 1,3-BHPB and dioxanes in these compounds (2:1) is estimated from 1 H-NMR spectra. In contrast with these complexes, 1,4- BHPB and 1,4-dioxane form a compound in 1:1 ratio (m.p. 98–99°). Pyridine and 1,3- or 1,4-BHPB furnishes 1:1 complexes with m.p. 60° and 65–66°, respectively. The BHPB-pyridine complexes are recrystallized from petroleum ether and afford well formed colorless crystals which sublime in vacuo. 1,4-BHPB and Me 2 SO afford a 1:1 complex with m.p. 104°.