Gerald M. Brooke

The preparation and properties of polyfluoro aromatic and heteroaromatic compounds

Abstract This review is concerned with ring systems formally recognised as “aromatic” and possessing a large proportion of fluorine atoms directly attached to the carbon skeleton. These include derivatives of the following: benzene and polynuclear benzenoid systems; pyridine, diaza- and triazabenzenes and some of their fused six-membered ring compounds; and a wide variety of fused ring carbocycles and heterocycles. Some highly fluorinated non-benzenoid aromatic compounds obeying the Huckel 4n + 2 π electron rule, as well as antiaromatic 4n π electron systems, are included in the survey. The wide variety of methods used for synthesising these highly fluorinated compounds, which enabled them to be regarded no longer as mere chemical curiosities, is presented. The chemical behaviour of polyfluoro aromatic and heteroaromatic compounds, at the fluorinated ring, forms the major proportion of this review: reactions with nucleophiles and a rationalisation of orientation reactions; reactions with electrophiles, free radicals, carbenes and nitrenes; the formation of stable salts of radical cations; photochemical reactions and the formation of valence isomers; and rearrangement reactions. Organometallic derivatives of polyfluorinated compounds have been extensively used in organic synthesis.

Partially fluorinated heterocyclic compounds. Part 26[1]. An investigation into the mode of cyclisation in the reaction of lithium 1,3,4,5,6,7,8-heptafluoro-2-naphthalenethiolate with dimethyl acetylenedicarboxylate

Abstract Octafluoronaphthalene reacted with sodium hydrosulphide to give 1,3,4,5,6,7,8-heptafluoro-2-naphthalenethiol (4). The lithium salt of (4) and dimethyl acetylenedicarboxylate gave dimethyl 4,5,6,7,8,9-hexafluoronaphtho[2,1-b]thiophen-1,2- dicarboxylate (6) and dimethyl 4,5,6,7,8,9-hexafluoronaphtho[2,3-b] thiophen-2,3-dicarboxylate (7) in the ratio of 92:8 respectively via intramolecular cyclisation reactions. Compound (6) was converted to 4,5,6,7,8,9-hexafluoronaphtho [2,1-b] thiophen (8) via hydrolysis and decarboxylation. Sodium methoxide in methanol replaced the fluorine at 6-F in 1,3,4,5,6,7,8-heptafluoro-2-naphthyl methyl sulphide (12). The preferred formation of (6) via the replacement of the fluorine at 1-F in the intermediate (5) indicates that localisation energy considerations enhance the selectivity of this orientation reaction.

A versatile process for the syntheses of very long chain alkanes, functionalised derivatives and some branched chain hydrocarbons

An earlier method for synthesising very long straight-chain alkanes of very specific lengths has been improved to give, in some cases, gram amounts of materials. Eleven compounds have been made: C98H198, C122H246, C162H326, C194H390, C198H398, C210H422, C242H486, C246H494, C258H518, C294H590 and C390H782. The self-condensation reaction of one of the intermediate aldehydes enabled two chain-branched hydrocarbons to be obtained: C96H193CHRC94H189 where R = CH3 and CH3(CH2)3. Three long-chain compounds containing carboxylic acid groups have been prepared: CH3(CH2)190CO2H,HO2C(CH2)48CO2H and HO2C(CH2)192CO2H.

The preparation and reactions of 1,3,4,5,6,7,8-heptafluoro-2-naphthyl prop-2-enyl ether: Formation of 1,3,4,5,6,7,8-heptafluoro-1-(prop-2-enyl)naphthalen-2-one and the photolysis and pyrolysis of this ketone [1].

Abstract 1,3,4,5,6,7,8-Heptafluoro-2-naphthyl prop-2-enyl ether (8) was isomerised in boiling xylene to 1,3,4,5,6,7,8-heptafluoro- 1-(prop-2-enyl)naphthalen-2-one (9). Photolysis of (9) gave 2,5,7-trifluoro-3,4-(tetrafluorobenzo)tricyclo[3.3.1.O 2,7 ]non-3- en-6-one (11) (by a [2 + 2] addition) and 1,2,7-trifluoro-3,4- (tetrafluorobenzo) tricyclo [3.3.1.O 2,7 ]non-3-en-8-one (12) (via an initial [3,5] photochemically-allowed sigmatropic shift). Pyrolysis of (9) at 455° also gave (11), while at 490°, both (9) and (11) gave 1-fluorovinyl 4,5,6,7,8-pentafluoro-1-naphthyl ketone (19).

The attempted synthesis of polyparatetrafluorophenylene vinylene via water-soluble and organic solvent-soluble precursor polymers

Abstract 2,3,5,6-Tetrafluoro-1,4-xylene-αα′-bis(dimethylsulphonium bromide) (5) and the related -αα′-bis(diethylsulphonium chloride) (6) were prepared by the reaction of αα′-dibromo-2,3,5,6-tetrafluoro-1,4-xylene (7) with dimethyl sulphide and of αα′-dichloro-2,3,5,6-tetrafluoro-1,4-xylene (7a) with diethyl sulphide, respectively. Compound (5) with aqueous alkali was converted into the dibromo compound (7), with no evidence of polymer being formed. Compound (6) failed to give any viable product with aqueous alkali. 2,3,5,6-Tetrafluorobenzene was converted into 1,4-diallyl-2,3,5,6-tetrafluorobenzene (14) via a copper (I) intermediate, and gave 2,3,5,6-tetrafluorobenzene-1,4-diethanal (13) on treatment with ozone. Reaction of 1,4-dilithio-2,3,5,6-tetrafluorobenzene (12) with the dialdehyde (13) failed to give a viable polymer soluble in organic solvents

2,3,4,5,7-pentafluorotricyclo(3.3.1.02,7) non-3-en-6-one, an internal Diels-Alder adduct from the Claisen rearrangement intermediate from pentafluorophenyl prop-2-enyl ether

Abstract The title compound (3), the first carbocyclic Diels-Alder adduct to be isolated from the Claisen rearrangement intermediate from the thermolysis of an aryl prop-2-enyl ether, has been characterised from its spectroscopic data and by its conversion to 1,2,3,4,7-pentafluorotricyclo [3.3.1.0 2,7 ]non-3- en-8,8 diol hemihydrate (5).

Partially fluorinated heterocycles. Part 25[1]. The formation of fused-ring 3H-azepine derivatives: 6,7,8,9-Tetrafluoro-2,4-diphenyl-3H-1-benzazepine and 6,7,8,9,10,11-hexafluoro-2,4-diphenyl-3H-naphth[2,1-b] azepine

Abstract Pentafluoroaniline(1) and 1,3,4,5,6,7,8-heptafluoro-2-naphthylamine(2) react with acetophenone in tetralin at reflux temperature in the presence of anhydrous zinc chloride to give the 3 H -azepine derivatives 6,7,8,9-tetrafluoro-2,4,-diphenyl-3 H -1-benzazepine (5) and 6,7,8,9,10,11-hexafluoro-2,4,-diphenyl-3 H -napth[2,1-b]azepine (6) respectively, in addition to the Schiff bases (3) and (4), found previously. The self-condensation product of acetophenone, β-benzoyl-α-methylstyrene (“dypnone”), is an intermediate in the ring-forming reactions. The heterocycles (5) and (6) exhibit fluxional behaviour which at 297K is fast for (5) but slow for (6) on the NMR time-scale.

Syntheses of very long chain alkanes terminating in polydeuterium-labelled end-groups and some very large single-branched alkanes including Y-shaped structures

Abstract Five alkanes containing very long chains have been synthesised: two deuterium-containing straight chain alkanes C 12 D 25 –(CH 2 ) m –CHDC 11 H 23 ( A , m =144 and B , m =192); two Y-shaped alkanes CH 3 (CH 2 ) 119 CHR(CH 2 ) 117 CH 3 [ C , R=–(CH 2 ) 60 CH 3 and D , R=–(CH 2 ) 194 CH 3 almost symmetrical molecules; and one alkane with an asymmetrically branched methyl group attached to the long chain E , CH 3 (CH 2 ) 191 CH(CH 3 )(CH 2 ) 98 CH 3 . Compound D(C 434 H 870 ) is the largest hydrocarbon to have been characterised in this work.

Partially fluorinated heterocyclic compounds. Part 15 [1]. Further preparations of furan derivatives from pentafluorophenyl- and 1,3,4,5,6,7,8-heptafluoro-2-naphthyl prop-2-ynyl ethers. The isolation of the claisen rearrangement intermediate 1,3,4,5,6,7,8-heptafluoro-1-(propa-1,2-dienyl)-naphthalen-2-one

Abstract 1,3,4,5,6,7,8-Heptafluoro-2-naphthyl prop-2-ynyl ether (5) and boiling isopropylbenzene gives 1,3,4,5,6,7,8-heptafluoro-1-(propa-1,2-dienyl)naphthalen-2-one (9) and two isomeric 2-(isopropylbenzyl)-4,5,6,7,8,9-hexafluoronaphtho [2,1-b]furans (11). Di-(4,5,6,7,8,9-hexafluoronaphtho [2,1-b]furan-2-ylmethyl) ether (17) and bis-(4,5,6,7,8,9-hexafluoronaphtho [2,1-b]furan-2-y1)methane (18) are formed from (5) in CF 2 ClCFCl 2 at 137°. The solvolysis of 2-fluoromethyl-4,5,6,7,8,9-hexafluoronaphtho-[2,1-b]furan (10) in water at 145–156° yields (17) (2%), (18) (37%) and 4,5,6,7,8,9-hexafluoronaphtho[2,1-b]furan-2-ylmethyl alcohol (19) (13%). Pentafluorophenyl prop-2-ynyl ether (1) reacts in either C 6 F 6 or CF 2 ClCFCl 2 at 140° to give di-(4,5,6,7-tetrafluorobenzo [b] furan-2-ylmethyl) ether (15). The major product from the solvolysis of 2-fluoromethyl-4,5,6,7-tetra-fluorobenzo [b] furan (2) in water at 140–142° is 4,5,6,7-tetra-fluorobenzo [b] furan-2-ylmethyl alcohol (16) (87%) accompanied by (15) (2.5%).

Spectroscopic studies of the novel conducting polymer polytetrafluorobenzo-c-thiophene

Abstract Tetra-fluorinated benzo-c-thiophene (or Isothianaphthalene) polymer of length distributed about 40 monomer units was studied over a wide range of oxidation levels using UV-visible-NIR and ESR spectroscopy. This soluble polymer proves to be a model system for the study of charged species on conducting polymers, free from the complications of branching, bulk confinement or inter chain interaction. Charging the oligomers can be seen to take place with carriers ranging between isolated radical cations (polarons) and interacting dicationic species (bipolarons).