Reaction of Sulfene wild Heterocyclic N,N-Disubstituted α-Aminomethylene Ketones IV. Synthesis of 3,4-Dihydro-5H-[1]benzothiopyratio [3,4-e]-1,2-oxathiin and 2,3,6,7-Tetrahydro-5H-thiopyrano[3,4-e]-1,2-oxathiin Derivatives

The reaction of sulfene with N,N-disubstituted 3-aminomethylene-2,3-dihydro-4-thiochromanones and-2,3,5,6-tetrahydro-4-thiopyranones gave 1,4-cycloadducts which are derivatives of new heterocyclic systems, namely 3,4-dihydro-5H-[1]benzothiopyrano[3,4-e]-1,2-oxathiin and 3,4,7,8-tetrahydro-5H-thiopyrano[3,4-e]-1,2-oxathiin, respectively. Furthermore, some pyrazole derivatives VII and VIII were prepared from 3-hydroxymethylene-2,3-dihydro-4-thiochromanone or 2,3,5,6-tetrahydro-4-thiopyranone and hydrazines.     

The photochemical synthesis of novel heterocyclic compounds from s-triazolo[4,3-b]pyridazine (II)

s-Triazolo[4,3-b Jpyridazine (I) photochemically reacted with dihydropyran; 2,3-dihydro-p-dioxin; 2,5-dihydrofuran; 2,5-dimethoxy-2,5-dihydrofuran; and 1,3-dioxep-5-ene to give a new series of substituted pyrrolo[1,2-b]-.s-triazoles (II-IX). In most reactions, two or more products were formed. The following compounds have been prepared from I: 9-methylene-4a,5,6,7,8a,9-hexahydropyrano[2,3 :4,5]pyrrolo[1,2-b]-s-triazole (Ha), the corresponding 9-cyanomethyl product (III), and 9-methylene-4a,7,8,8a-tetrahydro-6H,9H-pyrano[3′,2′:4,5]pyrrolo[1,2-b]-s-triazole (IIb) from dihydropyran; 9-methylene-4a,6,7,8a-tetrahydro-9H-p-dioxino[2′,3′:4,5]-pyrrolo[1,2-6]-s-triazole (IV) from 2,3-dihydro-p-dioxin; 8-methylene-4a,5,7a,8-tetrahydro-7H-furo[3′,4′:4,5]pyrrolo[1,2-b]-s-triazole (V) and the corresponding 8-cyanomethyl product (VI) from 2,5-dihydrofuran; 8-cyanomethyl-5,7-dimethoxy-4a,5,7a,8-tetrahydro-7H-furo[3′,4′:4,5]-pyrrolo[1,2-6]-s-lriazole (VII) from 2,5-dimethoxy-2,5-dihydrofuran; and 10-methylene-4a,5,9a,10-tetrahydro-9H-[1,3]dioxepino[5′,6′:4,5]pyrrolo[1,2-b]-s-triazole (VIII) and the corresponding 10-cyanomethyl product (IX) from 1,3-dioxep-5-ene. The addition of several other compounds (1,2,3,6-tetrahydropyridine, 1-acetylimidazole, 3-sulfolene, 2,3-dihydro-p-dithiin, and vinylene carbonate) was attempted, but no reactions were observed.     

Cycloaddition of 1-Aryl-3-trimethylsiloxy-1,3-butadienes in the Synthesis of Natural Quinone Analogs

7-Hydroxy-5-(2-methoxyphenyl)-2-methyl-6-R-1,4-naphthoquinones, 8-hydroxy-1-(2-methoxyphenyl)-3-oxo-1,2,3,4-tetrahydro-9,10-anthraquinone, and 2-ethoxycarbonyl-8-hydroxy-1-(2-methoxyphenyl)-3-trimethylsiloxy-1,1a,4,4a-tetrahydro-9,10-anthraquinone were synthesized by reactions of 1-(2-methoxyphenyl)-2-R-3-trimethylsiloxy-1,3-butadienes with 2-bromo-5-methyl-1,4-benzoquinone and juglone. 1-Aryl-2-ethoxycarbonyl-3-trimethylsiloxy-1,3-butadienes reacted with 1,4-naphthoquinone to afford 1-aryl-2-ethoxycarbonyl-3-hydroxy-9,10-anthraquinones and their 4,4a-dihydro derivatives.     

Acid-catalysed,nucleophile-catalysed and thermal decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone

The course of the thermal, acid-catalysed and iodide-catalysed decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone (III) was investigated. Thermal and iodide-catalysed decompositions gave mainly 2,3-diamino-1,4-naphthoquinone (VI) and 2-amino-3-(2′-methylallylamino)-1,4-naphthoquinone (V) together with low amounts of 2,2-dimethyl-1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline (IV) and 2-isopropyl-1H-naphthoimid-azole-4,9-dione (VII). The acid catalysed isomerization of the aziridinonaphthoquinone III with halohydric acids or with acetic acid readily gave the opening of the aziridine ring; the corresponding salts of 2-amino-3-(2′-haloisobutylamino)-1,4-naphthoquinones (VIIIa-c) and 2-amino-3-(2′-acetoxyisobutylamino)-1,4-naphthoqunone (X) were formed by cleavage of the carbon-nitrogen bond at the substituted carbon atom. Hypotheses on the mechanism of these reactions are given.     

Polyfluorinated heterocyclic compounds

The treatment of 2-phenyl-4-carbomethoxy-6,7,8,9-tetrafluorobenz[f]oxazepin-1,3 (I), 3-benzamido-5,6,7,8-tetrafluorocoumarin (V), and α-benzamido-β-(2-hydroxy-3,4,5,6-tetrafluorophenyl)-acrylic acid (III) with a mixture of glacial acetic acid and a mineral acid gave (IV), the π-complex of 3-hydroxy-5,6,7,8-tetrafluorocoumarin (VII) and benzoic acid. Treatment of (IV) with acetic anhydride gave 3-acetoxy-5,6,7,8-tetrafluorocoumarin (VI) and benzoic acid. Treatment with diazomethane gave 3-methoxy-5,6,7,8-tetrafluorocoumarin (VIII) and methyl benzoate. IV was also obtained from an equimolar mixture of its components. A mechanism for the formation of IV from I is proposed.     

Thermal decomposition of 2-amino-3-aziridino-1,4-naphthoquinones

The course of the thermal decomposition of various 2-amino-3-substituted aziridino-1,4-naphthoquinones (Ia-g) was investigated. In all the cases, the thermal decomposition gave variable amounts of 2,3-diamino-1,4-naphthoquinone (II) and of substituted 1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline-5,10-diones (IIIa-g) with complete stereospecificity. The decomposition of the aziridines Ib,f also gave significative amounts of 2-amino-3-allylamino-1,4-naphthoquinones (IVb,f). In the case of 2-amino-3-(2′-phenyl-3′-ethylaziridino)-1,4-naphthoquinone (Ig), the formation of trans-1-phenyl-1-butene (V), 2-(1-phenylpropyl)-1H-naphtho-imidazole-4,9-dione (VI), 2-phenyl-3-ethyl-3,4,5,10-tetrahydrobenzo[g]quinoxaline-5,10-dione (VII), 2-phenyl-3-ethyl-5,10-dihydrobenzo[g]quinoxaline-5,10-dione (VIII), and a mixture of cis- and trans-4H-2,3,5,6-tetra-hydro-2-phenyl-3-ethyl-5-iminonaphtho[1,2-b]oxazin-6-one (IX) also occurred. Hypotheses concerning the mechanism and the steric course of this reaction are given. The reaction is a general method for the stereospecific synthesis of 2,3-disubstituted 1,2,3,4,5,10-hexahydrobenzo[g]quinoxalines.     

Benzofused tricycles based on 2-quinoxalinol

This paper describes our recent efforts to synthesize novel compound scaffolds integrating 2-quinoxalinol with privileged structures of 1,3-dihydro-benzoimidazol-2-one, 1,3-dihydro-benzoimidazole-2-thione, 3-hydroxy-1H-quinoxalin-2-one, 2H-benzo[1,4]oxazin-3-ol, 2H-benzo[1,4]thiazin-3-ol, and 1,3,4,5-tetrahydro-benzo[1,4]diazepin-2-one, respectively. Eight novel benzofused tricycles and their substituent diversity points were developed. These include pyrazino[2,3-g]quinoxaline-2,8-diol (I), 3-hydroxy-6,8,9,10-tetrahydro-1,4,6,10-tetraaza-cyclohepta[b]naphthalen-7-one (II), 6-hydroxy-4H-1-oxa-4,5,8-triaza-anthracen-3-one (III), 6-hydroxy-4H-1-thia-4,5,8-triaza-anthracen-3-one (IV), 6-hydroxy-1,1-dioxo-1,4-dihydro-2H-1lambda(6)-thia-4,5,8-triaza-anthracen-3-one (V), 6-hydroxy-1,3-dihydro-imidazo[4,5-g]quinoxalin-2-one (VI), 6-hydroxy-1,3-dihydro-imidazo[4,5-g]quinoxaline-2-thione (VII), and 7-hydroxy-1,4-dihydro-pyrazino[2,3-g]quinoxaline-2,3-dione (VIII). This strategy of integrating two benzofused privileged structures into one molecule may provide a greater chance for the discovery of novel lead compounds.     

Reaction of dichloroketene and sulfene with N,N-disubstituted α-aminomethyleneketones. Synthesis of pyrano[2,3-e]indazole and 1,2-oxathiino[6,5-e]indazole derivatives

The polar 1,4-cycloaddition of dichloroketene to N,N-disubstituted (E)-5-aminomethylene-1,5,6,7-tetrahydro-(1-methyl)(1-phenyl)-4H-indazol-4-ones V, prepared from 1,5,6,7-tetrahydro-(1-methyl)(1-phenyl)-4H-indazol-4-ones via the 5-hydroxymethylene derivatives, gave in good yield N,N-disubstituted 4-amino-3,3-dichloro-4,5,6,7-tetrahydro-(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-(3H)ones VI, which are derivatives of the new heterocyclic system pyrano[2,3-e]indazole. Dehydrochlorination of VI with DBN afforded N,N-disubstituted 4-amino-3-chloro-6,7-dihydro(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-2(5H]-ones VII generally in satisfactory yield. Full aromatization with DDQ of VII was tried only in the case of dimethylamino derivatives, giving a moderate yield of 3-chloro-4-dimethylamino(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-2(7H)-ones. Cycloaddition of sulfene to V occurred only in the case of aliphatic N-substitution to give in moderate yield 4-dialkylamino-4,5,6,7-tetrahydro-(7-methyl)(7-phenyl)-3H-1,2-oxathiino[6,5-e]indazole 2,2-dioxides, which are derivatives of the new heterocyclic system 1,2-oxathiino[6,5-e]indazole.     

2,5-Dihydro-1H-4-methylnaphtho[2,3-b]-1,4-diazepine-2,6,11-trione. Reaction with methanol

The reaction of 2,3-diamino-1,4-naphthoquinone with acetoacetic ester in toluene (with water separation) gave 2,5-dihydro-1H-4-methylnaphtho[2,3-b]-1,4-diazepine-2,6,11-trione, which adds a molecule of methanol to the C=C bond of the diazepine ring to give 2,3,4,5-tetrahydro-1H-4-methyl-4-methoxynaphtho-[2,3-b]-1,4-diazepine-2,6,11-trione.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 121–123, January, 1979.     

Studies on the syntheses of analgesics. Part XXXIX . Synthesis of 1,2,3,4,5,6- Hexahydro-8-hydroxy -2,6-methane-3,6,1 1-trimethyl-2,3-benzo|g| diazocine and 1,2,3,4,5,10,11,12-Octahydro-7-hydroxy-1,5-dimethylpyridazino|2,3-b| isoquinoline |studies on the syntheses of heterocyclic compounds. Part LXI |

1,2,3,4,5,6-Hexahydro-8-hydroxy-2,6-methano-3,6,1 1-trimethyl-2,3-benzo |g| diazocine (IV) and 1,2,3,4,5,10,11,12-octahydro-7-hydroxy-1,5-dimethylpyridazino |2,3-b| isoquinoline (VI) were synthesized from a common intermediate, 3-(3-methoxyphenyl)-2-butanone (VII), through several steps. Reaction of VII with ethyl bromoacetate gave the mixture of ethyl 4-keto-3-(3-methoxyphenyl)-3-methylpentanoate (XIV) and ethyl 4-keto-5-(3-methoxyphenyl)hexanoate (XV) which were hydrolyzed and condensed with methylhydrazine to give the 4,5-dihydro-5-(3-methoxyphenyl)-2,5,6-trimethyl- (XVIII) and 4,5-dihydro-6-(3-methoxy-α-methylbenzyl)-2-methylpyridazine-3(2H)one (XIX). Reduction of XVIII and XIX followed hy cyclization afforded the 2,3-benzo |g| diazocine (XXII) and the pyridazino |2,3-b| isoquinoline (XXIII) which on treatment with 47% hydrobromine acid afforded the phenolic bases (IV and VI), respectively. The mass spectrum of IV, VI, XXII and XXIII was also discussed.     

The synthesis of benzofuroquinolines. III. Two dihydroxybenzofuroquinolinones

Two dihydroxybenzofuroquinolinones, 3,9-dihydroxy-5H-benzofuro[3,2-c]quinolin-6-one (V) and 3,8-dihydroxy-6H-benzofuro[2,3-b]quinolin-11-one (VI), were obtained by the demethyl-cyclization of 3-(2,4-dimethoxyphenyl)-4-hydroxy-7-methoxy-1H-quinolin-2-one (IV). By the methylation with diazomethane, V gave a dimethylated compound (VII), while VI gave a trimethylated compound (VIII).     

Synthesis of 5,6,7,8-tetrahydro-5-oxopyrido[2,3-d]pyrimidine-6-carbonitriles and -6-carboxylic acid esters

Dieckmann ring closure reactions of 4-[(2-cyanoethyl)substituted amino]-2-phenyl-5-pyrimidinecarboxylates (Ha-f) afforded several 5,6,7,8-tetrahydro-5-oxo-2-phenylpyrido[2,3-d]pyrimidine-6- carbonitriles (IIIa-f). The open-chain intermediates (IIa-f) were prepared by dechloroamination of 5-carbethoxy-4-chloro-2-phenylpyrimidine (1a) with several 3-substituted amino- propionitriles. Alkylation of the sodium salt of 5,6,7,8-tetrahydro-8-methyl-5-oxo-2-phenyl-pyrido[2,3-d]pyrimidine-6- carbonitrile (IIIa) with methyl iodide in DMF resulted in methylation at C-6 to afford IV. Tosylation of IIIa in pyridine gave the corresponding tosyl ester (V) of the enolic form. Oxidative dehydrogenation at the 6,7-position resulted when IIIa reacted with thionyl chloride, affording 5,8-dihydro-8-methyl-5-oxo-2-phenylpyrido[2,3-d]pyrimidine-6- carbonitrile (VII). Dechloroamination of la or 5-carbethoxy-4-chloro-2-methylthiopyrimidine (Ib) with ethyl 3-ethylaminopropionate followed by Dieckmann cyclization of the resulting open-chain intermediates gave the corresponding ethyl 5,6,7,8-tetrahydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxylates IX'a and IX'b, respectively. These exist predominately in the enol form and undergo alkylation and oxidation reactions similar to IIIa.     

Acyclopyrimidine C-nucleosides. Synthesis of acyclopseudoisocytidine and its derivatives

Acyclopseudouridine (IV), acyclopseudoisocytidine (VII), and their 1-methyl derivatives (V and VIII) were synthesized from 5-hydroxymethyluracil (I). Acyclopseudouridine (IV) was conveniently prepared from the condensation of 5-hydroxymethyluracil ( I ) with ethylene glycol under acidic condition. Compound IV also could be prepared from 5-chloromethyluracil, however, this procedure was found to be inferior to the direct condensation method. Methylation of IV with dimethylformamide dimethyl acetal gave 1,3-dimethylacyclopseudouridine (VI) which was subsequently converted to acyclopseudoisocytidine (VII). 1-Methyl derivatives V and VIII were obtained from the selective methylation of IV and VII, respectively. 5-Hydroxymethyluracil also reacted with 2-mercaptoethanol to give the sulfide derivative (IX).     

Synthesis of 1H-naphth[2,3-d]imidazole-4,9-diones by acid catalyzed cyclization of 2-Acylamino-3-amino-1,4-naphthoquinones

The conversion of 2-acylamino-3-amino-1,4-naphthoquinones (II) to the corresponding 2-substituted 1H-naphth[2,3-d]imidazole-4,9-diones (I) under both alkaline and acid catalyzed conditions has been effected and the results compared. Treatment of 3-(4′-chlorobutanonyl-amino)-3-amino-1,4-naphthoquinone (He) with aqueous ethanolic sodium hydroxide solution gives 1,2-butanonaphth[2,3-d]imidazole-4,9-dione (V); whereas, treatment of lie with refluxing formic acid gave 2-(4′-chlorobutyl)-1H-naphth[2,3-d]imidazole-4,9-dione. Treatment of 2-substi-tuted 1H-naphth[2,3-d]imidazole-4,5-diones in DMF with alkyl halides in the presence of potassium carbonate affords the expected 1,2-disubstituted naphth[2,3-d]imidazole-4,9-diones (VI). The spectral properties of I, II, V and VI as well as those of some 2-acylamino-3-chloro-1,4-naphthoquinones IV are discussed.     

The synthesis of pyridazino[4,5-d] pyridazines,pyrazino [2,3-d] pyridazines and a pyrimido [4,5-d] pyridazine

The synthetic chemistry of the relatively unknown pyridazino [4,5-d]pyridazine ring system has been extended. 1,4-Diaminopyridazino [4,5-d]pyridazine (VIII) has been prepared by two routes, the most interesting of these being the one-step conversion of 4,5-dicyanopyridazine into VIII with hydrazine. Upon nitration VIII gave only the mononitramine (X). Attempts to prepare 1,4-dichloropyridazino [4,5-d]pyridazine gave only 4-chloro-2H-pyridazino [4,5-d]pyridazin-1-one (XII). Pyrimido [4,5-d]pyridazine-1,3-dione (XIV) was prepared from pyridazine-4,5-dicarboxamide (IV). The hydrolysis of 5,8-dichloropyrazino [2,3-d]pyridazine (XV) gave 5-chloropyrazino [2,3-d]pyridazin-8-one (XVII) and likewise the ammonolysis of XV gave 5-amino-8-chloropyrazino [2,3-d]pyridazine (XX). As expected the hydrolysis of 5,8-dibromo-pyrazino [2,3-d]pyridazine (XXI) gave 5-bromopyrazino [2,3-d]pyridazin-8-one (XXII). Attempted catalytic dechlorination of 5-chloropyrazino [2,3-d]pyridazin-8-one (XVII) gave 1,2,3,4-tetrahydropyrazino [2,3-d]pyridazin-5-one (XIX).     

Synthesis of 9-Deoxynanaomycin,a Methyl Ester via 1,2-Ketone Transposition

The title compound, methyl trans 1-methyl-5,10-dioxo-3,4,5,10-tetrahydro-1H-naphthol[2,3-c] pyran-3-yl-acetate has been synthesised using the key intermediate, 1-(1,4-dimethoxy-2-naphthyl)-2-oxo-4-acetoxybutane, prepared through 1,2-ketone transposition of the 1-(1,4-dimethoxy-2-naphthyl)-4-acetoxy-1-butanone.     

Synthesis of a new polyfluorinated vinylogue of tetrathiafulvalene through 1,3-dipolar cycloaddition of ethyl beta-bromoperfluorodithiocrotonate with dimethyl acetylenedicarboxylate

The ethyl ester of beta-bromoperfluorodithiocrotonic acid reacts with dimethyl acetylenedicarboxylate to give 1,4-difluoro-2,3-bis(trifluoromethyl)-but-2-ene-1,4-diylidene-2,2'-bis(4',5'-dicarbomethoxy-1',3'-dithiole) (4), a new type of vinylogue of tetrathiafulvalene. The thermal transformations of this compound lead, depending on the temperature, to the formation of the cyclization products: 11,14-difluoro-2,3,8,9-tetra(carbomethoxy)-12,13-bis(trifluoromethyl)-1,4,7,10-tetrathiadispiro[4.0.4.4]tetradeca-2,8,11,13-tetraene (8) or 5,8-difluoro-6,7-bis(trifluoromethyl)-2,3-bis(carboxymethyl)-1,4-benzodithiine (11).     

Polyfluorinated heterocyclic compounds

The treatment of 2-phenyl-4-carbomethoxy-6,7,8,9-tetrafluorobenz[f]oxazepin-1,3 (I), 3-benzamido-5,6,7,8-tetrafluorocoumarin (V), and -benzamido--(2-hydroxy-3,4,5,6-tetrafluorophenyl)-acrylic acid (III) with a mixture of glacial acetic acid and a mineral acid gave (IV), the -complex of 3-hydroxy-5,6,7,8-tetrafluorocoumarin (VII) and benzoic acid. Treatment of (IV) with acetic anhydride gave 3-acetoxy-5,6,7,8-tetrafluorocoumarin (VI) and benzoic acid. Treatment with diazomethane gave 3-methoxy-5,6,7,8-tetrafluorocoumarin (VIII) and methyl benzoate. IV was also obtained from an equimolar mixture of its components. A mechanism for the formation of IV from I is proposed.For part II, see [1].     

Synthesis, structure and cytostatic activity of a series of N-substituted 3,4-diphenyl-1H-pyrrole-2,5-diones

A series of N-substituted 3,4-diphenyl-1H-pyrrole-2,5-diones (diphenylmaleimides) (IV) were synthesized and tested for cytostatic activity. Compounds IVa--k were prepared from diphenylmaleic anhydride or its dinitro derivative (V or VI) and the corresponding amine. Compounds IVl--n were obtained by reaction of 3-(p-nitrophenyl)-4-phenyl-1H-pyrrole-2,5-dione potassium salt with the appropriate chloroalkylamine. Hydrogenation of IVl,n gave the the corresponding cis-3-(p-aminophenyl)-4-phenylsuccinimides (VIIIa,b). The structure-cytostatic activity relationship of these compounds is discussed.     

Reactions of tetrafluoroethylene oligomers. Part 1. Some pyrolytic reactions of the pentamer and hexaher and of the fluorine adducts of the tetramer and pentamer

Pyrolyses of these highly branched fluorocarbons over glass beads caused the preferential thermolyses of CC bonds where there is maximum carbon substitution. Fluorinations of perfluoro-3,4-dimethylhex-3-ene (tetramer) (I) and perfluoro-4-ethyl-3,4-dimethylhex- 2-ehe (pentamer) (II) over cobalt (III) fluoride at 230° and 145° respectively afforded the corresponding saturated fluorocarbons (III) and (IV), though II gave principally the saturated tetramer (III) at 250°. Pyrolysis of III alone at 500—520° gave perfluoro-2-methylbutane (V), whilst pyrolysis of III in the presence of bromine or toluene afforded 2-bromononafluorobutane (VI) and 2H-nonafluorobutane (VII) respectively. Pyrolysis of perfluoro-3-ethyl-3, 4-dimethylhexane (IV) alone gave a mixture of perfluoro-2-methylbutane (V), perfluoro-2-methylbut-1-ene (VIII), perfluoro-3-methylpentane (IX), perfluoro-3,3-dimethylpentane (X), and perfluoro-3,4- dimethylhexane (III). Pyrolysis of IV in the presence of bromine gave (VI) and 3-bromo-3-trifluoromethyl-decafluoropentane (XI): with toluene, pyrolysis gare VlI and 3H-3-trifluoromethyldecafluoropentane (XII). Pyrolysis of II at 500° over glass gave perfluoro-1,2,3-trimethylcyclobutene (XIII) and perfluoro-2,3-dimethylpenta-1,3(E)- and (Z)-diene (XIV) and (XV) respectively. The diene mixture (XIV and XV) was fluorinated with CoF₃ to give perfluoro-2,3-dimethylpentane (XVI) and was cyclised thermally to give the cyclobutene (XIII). Pyrolysis of perfluoro-2- (1′-ethyl-1′-methylpropyl)-3-methylpent-1-ene (XVII) (TFE hexamer major isomer) at 500° gave perfluoro-1-methyl-2-(1′-methylpropyl)cyclobut-1-ene (XVIII) and perfluoro-2-methyl-2-(1′-methylpropyl)buta-1,3-diene (XIX). Fluorination of XVIII over CoF₃ gave perfluoro-1-methyl-2- (1′-methylpropyl)cyclobutane (XX), which on co-pyrolysis with bromine gave VI. XIX on heating gave XVIII. Reaction of XVIII with ammonia in ether gave a mixture of E and Z 1′-trifluoromethyl-2-(1′-trifluoromethyl- pentafluoropropyliden-1′-yl)tetrafluorocyclobutylamine (XXI) which on diazotisation and hydrolysis afforded 2-(2′trifluoromethyl- tetrafluorocyclobut-1-en-1′-yl)-octafluorobutan-2-ol (XXII).