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).     

Some reactions of tetrafluoroethylene oligomers

As part of a programme to prepare and evaluate a series of perfluoro- chemicals for use as inert fluids, the fluorinations of some tetrafluoroethylene oligomers over cobalt (III) fluoride have been studied.Fluorination of perfluoro-3,4-dimethylhex-3-ene (tetramer) and perfluoro-4-ethyl-3,4-dimethylhex-2-ene (pentamer) over CoF₃ at 230°C and l45°C respectively afforded the corresponding saturated fluorocarbons however, at 250°C, pentamer gave predominantly the saturated tetramer. The thermal behaviour of these saturated fluorocarbons alone and in the presence of bromine and toluene has been studied.Pyrolysis of pentamer over glass beads at 500°C gave perfluoro-1,2,3- trimethylcyclobutene and isomers of perfluoro-2,3-dimethylpenta-1,3- diene. Under similar conditions perfluoro-2-(1-ethyl-1-methylpropyl). 3-methylpent-1-ene (hexamer) gave perfluoro-1-methyl-2-(1-methyl- propyl)-cyclobut-1-ene and perfluoro-2-methyl-3-(1-methylpropyl)-buta- 1,3-diene.These reactions and the structural elucidation of the products will be discussed.     

Polyfluorinated hydrazones in organic synthesis

A preparative one-step method for the synthesis of 1,1,1,5,5,5-hexafluoro-4-trifluoromethylpentane-2,3-dione dihydrazone from perfluoro-4-methylpent-2-ene and hydrazine hydrate has been developed. Oxidation of this dihydrazone with bromine in water gives 3-diazo-1,1,1,5,5,5-hexafluoro-4-trifluoromethylpentane-2-one. The same product is obtained from 3-hydrazono-1,1,1,5,5,5-hexafluoro-4-trifluoromethylpentane-2-one under similar conditions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2039–2041, November, 1994.This work was supported by the Russian Foundation for Basic Research (the project code 94-03-08548).     

Guanidine in the synthesis of perfluoroalkylpyrimidines and perfluoroalkyl-s-triazines

Perfluoro-2-methylpent-2-ene and perfluoro-5-azanon-4-ene react with guanidine hydrochloride in the presence of triethylamine to give 2-amino-6-fluoro-4-pentafluoroethyl-5-trifluoromethylpyrimidine and 2-amino-4,6-bis(heptafluoropropyl)-1,3,5-triazine, respectively. The structure of the former product was confirmed by X-ray diffraction analysis.     

Chemical modification of usnic acid 1. Reaction of (+)-usnic acid with perfluoroolefins

The reactions of the natural lichen metabolite, (+)-usnic acid, with a series of commercially available polyfluoroolefins (tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropene, perfluoro-2-methylpent-2-ene, and 1,2-dichlorooctafluorocyclohex-1-ene) afford its 7-O-polyfluoroalkyl and perfluorovinyl ethers. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1198–1202, June, 2007.     

Gas-phase rate coefficients for the reactions of nitrate radicals with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene at room temperature

Rate coefficients for reactions of nitrate radicals (NO3) with (Z)-pent-2-ene, (E)-pent-2-ene, (Z)-hex-2-ene, (E)-hex-2-ene, (Z)-hex-3-ene, (E)-hex-3-ene and (E)-3-methylpent-2-ene were determined to be (6.55 +/- 0.78)x 10(-13) cm3 molecule(-1) s(-1), (3.78 +/- 0.45)x 10(-13) cm3 molecule(-1) s(-1), (5.30 +/- 0.73)x 10(-13) cm(3) molecule(-1) s(-1), (3.83 +/- 0.47)x 10(-13) cm(3) molecule(-1) s(-1), (4.37 +/- 0.49)x 10(-13) cm(3) molecule(-1) s(-1), (3.61 +/- 0.40)x 10(-13) cm3 molecule(-1) s(-1) and (8.9 +/- 1.5)x 10(-12) cm3 molecule(-1) s(-1), respectively. We performed kinetic experiments at room temperature and atmospheric pressure using a relative-rate technique with GC-FID analysis. The experimental results demonstrate a surprisingly large cis-trans(Z-E) effect, particularly in the case of the pent-2-enes, where the ratio of rate coefficients is ca. 1.7. Rate coefficients are discussed in terms of electronic and steric influences, and our results give some insight into the effects of chain length and position of the double bond on the reaction of NO3 with unsaturated hydrocarbons. Atmospheric lifetimes were calculated with respect to important oxidants in the troposphere for the alkenes studied, and NO3-initiated oxidation is found to be the dominant degradation route for (Z)-pent-2-ene, (Z)-hex-3-ene and (E)-3-methylpent-2-ene.     

Reactions of tetrafluorophthalic and difluoropyromellitic acids with sulphur tetrafluoride

Fluorination of tetrafluorophthalic acid (1) with an SF₄/HF mixture at 190–300°C afforded,beside the expected perfluoro-o-xylene (2) and perfluoro-o-toluyl fluoride (4), considerableamounts of octafluoro-1,3-dihydroisobenzofuran (3). The reaction with difluoropyromelliticacid (5) at 190°C gave a mixture of perfluoro-2,4,5-trimethylbenzoyl fluoride (9),perfluoro-2,5-dimethylterephthaloyl difluoride (10a), perfluoro-2,4-dimethylisophthaloyl difluoride(10b) and perfluoro-5-methyl-6-fluoroformyl-1,3-dihydroisobenzofuran (11), but at 300°C perfluorodurene (6), perfluoro-5,6-dimethyl-1,3-dihydroisobenzofuran (7) and perfluoro-2,4,5-trimethylbenzoyl fluoride (9) were obtained in a 3:1:0.8 ratio.     

Concise syntheses of cystothiazoles A, C, D, and melithiazol B

A convergent synthesis of cystothiazoles C 1 and D 3 was achieved based on Julia coupling between the functionalized aldehyde 5b, corresponding to left half of the final molecule, and aryl sulfone 6 or 7, bearing a bithiazole moiety, corresponding to right half. Methylation of 1 and 3 gave cystothiazole A 2 and melithiazol B 4, respectively. The overall yield (5 steps from (2R,3S)-3-methylpent-4-yne-1,2-diol 10; 57%) of 5b via the present route was improved in comparison to that of the previously reported functionalized aldehyde 5a (7 steps from 10; 13%). By applying the modified Julia coupling method, selectivity (6E/6Z=20 : 1-26 : 1) toward the (6E)-form of the coupled products (15 or 19) against the corresponding (6Z)-form was improved in comparison to the Wittig method (6E/6Z=4 : 1-6.9 : 1).     

Pyrolysis-GC/MS of Menthyl Esters of N-Benzoxycarbonyl Amino Acid

With the aid of a Pyrolysis-GC/TOF MS technique,the pyrolysis behaviour of two menthyl esters of N-benzoxycarbonyl amino acid was investigated.A clear pattern emerges involving the cleavage of the bond linking the menthyl ring to the carboxy group,followed by further degradation of the fragments.The major pyroproducts were p-menth-1-ene pyrolysed at a higher temperature or p-menth-2-ene pyrolysed at a lower temperature,and va-rious derivatives of cyclohexene pyrolyzed from the menthyl ring.In addition,some ...     

Reaction of perfluoro-2-methylpent-2-ene with ethylenediamine and hexamethylenediamine

Reaction of perfluoro-2-methylpent-2-ene with ethylenediamine and hexamethylenediamine results in 9-fluoro-5,9-bis(pentafluoroethyl)-6,8,8-tris(trifluoromethyl)-1,4-diazabicyclo[5.2.0]nona-4,6-diene, whose structure was confirmed by X-ray analysis, and 11-pentafluoroethyl-10-trifluoromethyl-1,8-diazabicyclo[7.2.0]undeca-8,10-diene, respectively. The reaction pathways are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1578–1582, August, 1999.     

Reaction of trifluoromethanesulfonamide with alkenes and cycloocta-1,5-diene under oxidative conditions. Direct assembly of 9-heterobicyclo[4.2.1]nonanes

Reactions of trifluoromethanesulfonamide with α-methylstyrene, 2-methylpent-1-ene, and cycloocta-1,5-diene in the system t-BuOCl-NaI were studied. In the reaction with α-methylstyrene 1-iodo-2-phenylpropan-2-ol was the only isolated product. The reaction with 2-methylpent-1-ene gave a mixture of N,N′-(2-methylpentane-1,2-diyl)bis(trifluoromethanesulfonamide), trifluoro-N-(2-hydroxy-2-methylpentyl)-methanesulfonamide, and N,N′-[oxybis(2-methylpentan-2,1-diyl)]bis(trifluoromethanesulfonamide). Trifluoromethanesulfonamide reacted with cycloocta-1,5-diene to produce a mixture of 2,5-diiodo-9-(trifluoromethylsulfonyl)-9-azabicyclo[4.2.1]nonane and 2,5-diiodo-9-oxabicyclo[4.2.1]nonane; this reaction may be regarded as the first example of direct assembly of bicyclononane skeleton.     

Synthesis of Enantiomerically Pure Bis(hydroxymethyl)-Branched Cyclohexenyl and Cyclohexyl Purines as Potential Inhibitors of HIV

The synthesis of the enantiomerically pure bis(hydroxymethyl)-branched cyclohexenyl and cyclohexyl purines is described. Racemic trans-4,5-bis(methoxycarbonyl)cyclohexene [(+/-)-6] was reduced with lithium aluminum hydride to give the racemic diol (+/-)-7. Resolution of (+/-)-7 via a transesterification process using lipase from Pseudomonas sp. (SAM-II) gave both diols in enantiomerically pure form. The enantiomerically pure diol (S,S)-7was benzoylated and epoxidized to give the epoxide 9. Treatment of the epoxide 9 with trimethylsilyl trifluoromethanesulfonate and 1,5-diazabicyclo[5.4.0]undec-5-ene followed by dilute hydrochloric acid gave (1R,4S,5R)-4,5-bis[(benzoyloxy)methyl]-1-hydroxycyclohex-2-ene (10). Acetylation of 10 gave (1R,4S,5R)-1-acetoxy-4,5-bis[(benzoyloxy)methyl]cyclohex-2-ene (11). (1R,4S,5R)-1-Acetoxy-4,5-bis[(benzoyloxy)methyl]cyclohex-2-ene (11) was converted to the adenine derivative 12 and guanine derivative 13 via palladium(0)-catalyzed coupling with adenine and 2-amino-6-chloropurine, respectively. Hydrogenation of 12 and 13 gave the correspondning saturated adenine derivative 14 and guanine derivative 15. (1R,4S,5R)-4,5-Bis[(benzoyloxy)methyl]-1-hydroxycyclohex-2-ene (10) was converted to the adenine derivative 16 and guanine derivative 17 via coupling with 6-chloropurine and 2-amino-6-chloropurine, respectively, using a modified Mitsunobu procedure. Hydrogenation of 16 and 17 gave the corresponding saturated adenine derivative 18 and guanine derivative 19. Compounds 12-19 were evaluated for activity against human immunodeficiency virus (HIV), but were found to be inactive. Further biological testings are underway.     

Corner Bromination of 2-Methyl-endo-tricyclo[3.2.1.0(2,4)]octane and -oct-6-ene

Reaction of 2-methyl-endo-tricyclo[3.2.1.0(2,4)]octane (1) with bromine in CCl(4) gave 2-exo,3-endo-dibromo-2-endo-methylbicyclo[3.2.1]octane (3) which rearranges on silica to 2-exo,6-endo-dibromo-1-methylbicyclo[2.2.2]octane (4). Reaction in methanol gave 4-endo-bromo-2-exo-methoxy-2-endo-methylbicyclo[3.2.1]octane (10) and 4-endo-bromo-2-endo-methoxy-2-exo-methylbicyclo[3.2.1]octane (11) formed by corner attack of the bromine electrophile with C2-C4 bond rupture and inversion of configuration at the site of electrophilic attack. Reaction of 2-methyl-endo-tricyclo[3.2.1.0(2,4)]oct-6-ene (2) with bromine in CCl(4) and methanol gave products of reaction at the alkene site.     

四氟乙烯齐聚体的反应: II.四氟乙烯五聚体和烯丙醇的反应及反应产物的转化

The reaction of perfluoro- (3, 4-dimethyl-3-ethylhexene-(2)) (1) with allyl alcohol under different conditions gave different products. Compound 1 reacted with sodium allyl alcoholate yielding 2-(1'-allyloxy-tetrafluoroethyl)-perfluoro(3-methyl-3-ethylpentene- (1))(2). In the presence of triethylamine, 1 reacted with allyl alcohol to give 2-allyloxy-perfluoro (3, 4-dimethy1-4-ethylhexene- (2))(3), and in the presence of acetone and K2CO3 to give compound 4. These reactions all gave allyl-3-trifluoromethyl-3- pentafluoroethyl-2,2-dihydro-pentafluorovalerate (5a) as byproduct. Compound 1 reacted with allyl alcohol in the presence of triethylamine at 20-22`C to give 2, at 30-35`C to give a mixture of 2 and 3 and at 35-40`C to give a mixture of 3 and 5a respectively. Compound 2 was transformed to compound 4 in acetone and in the psesence of K2CO3, \o\ compound 5a or 5b in the corresponding alcohol and to compound 6 on reacting with dimethylamine. Compound 2 as well as 3 was converted to perfluoro-(3-ethyl-2,3,4,5- tetramethyl-2,3-dihydrofuran) (7) by KF in sulpholane.     

Synthetic utility of 3-(perfluoro-1,1-dimethylbutyl)prop-1-ene. Part VI. A free-radical addition of CCl4 and CBr4 and dehydrohalogenation of the adducts

Heating the title compound 1 in excess CCl₄ and in the presence of a free-radical initiator (t-butyl peroxide) at 120 °C afforded 1,1,1,3-tetrachloro-4-(perfluoro-1,1-dimethylbutyl)butane (2) as the main product together with considerable amounts of cyclic dimer, 1,4-bis(perfluoro-1,1-dimethylbutyl)cyclohexane (3). Reaction of 1 with CBr₄ at 120 °C gave 1,1,1,3-tetrabromo-4-(perfluoro-1,1-dimethylbutyl)butane (4) as the sole product while at 220 °C a mixture of 1,2-dibromo-3-(perfluoro-1,1-dimethylbutyl)propane (5) and 1,1-dibromo-4-(perfluoro-1,1-dimethylbutyl)buta-1,3-diene (6) was formed. Treatment of adducts 2 and 4 with methanolic potassium hydroxide at ambient temperature gave mixtures of 1,1,3-trihalo-4-(perfluoro-1,1-dimethylbutyl)but-1-enes (7) or (8) and 1,1-dihalo-4-(perfluoro-1,1-dimethylbutyl)buta-1,3-dienes (9) or (6) in ratios depending on the adduct to base ratio and on the reaction conditions. Using an excess of the base and reflux temperature, adduct 4 and diene 6 were converted into methyl 4-(perfluoro-1,1-dimethylbutyl)buten-3-oate (10).     

EPR study of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes

The EPR method was used to study the structure of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes. The capacity for spin adducts to split off hydrogen atoms is determined by the degree of steric screening of the free radical center. The preparative photochemical reaction of hydrosilanes and dialkyl phosphites with perfluoro-4-methylpent-2-ene leads to regiospecific hydrosilylation and hydrophosphorylation products with yields up to 80%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1018–1023, May, 1991.     

Reactions of perfluoro(2-methylpent-2-ene) and perfluoro(5-azanon-4-ene) with primary amines containing a 2,6-di-tert-butylphenol fragment

Reactions of perfluoro(2-methylpent-2-ene) and perfluoro(5-azanon-4-ene) with 4-(2-aminoethyl)-2,6-di-tert-butylphenol and 4-(3-aminopropyl)-2,6-di-tert-butylphenol in acetonitrile in the presence of triethylamine gave the corresponding azetidine, 1,2-dihydroazete, and 1,2-dihydro-1,3-diazete derivatives, respectively. The reaction mechanisms, role of triethylamine, and factors affecting the intramolecular nucleophilic cyclization process are discussed.     

Fluorocyclohexanes. Part XVI. The six H-trifluoromethyldecafluoro- and two of the 2H,4H-trifluoromethylnonafluoro-cyclohexanes

Fluorination of benzotrifluoride by cobaltic fluoride at 260–280° gave, besides the fluorocarbon, the six possible tridecafluoromethylcyclohexane isomers, and two 2H,4H-dodecafluorides. Of the C₇HF₁₃ compounds, only the cis?2H-, and the cis- and trans-4H-isomers could be isolated pure. The two 3H-isomers were made by pyrolysis of perfluoro(1-methyl-3-isopropylcyclohexane) in the presence of toluene. The trans-2H-isomer was made by further fluorination of one of the 2H,4H-dodecafluorides. Aqueous potash and the cis-2H-tridecafluoride gave 1-trifluoromethylnonafluorocyclohex-1-ene, which with stronger alkali hydrolysed to 1-carboxynonafluorocyclohex-1-ene. The cis- and trans- 2H and 4H-tridecafluorides were dehydrofluorinated by sodium fluoride at 320–380° (the cis-isomer of each pair reacted faster than the trans- : axial versus equatorial hydrogen) to give, respectively, the 1-trifluoromethylnonafluoro-ene and the 4-trifluoromethyl-isomer. The latter was isomerised to the former by sodium fluoride at 500–600°. The 1?CF₃-ene gave hexafluoroglutaric acid on oxidation with alkaline potassium permanganate.     

Rearrangements in cobaltic fluoride fluorinations of cycloalkanes with seven or more ring carbons

Cyclo-heptane, -octane, -decane, -dodecane and -octadecane have been fluorinated in the vapour phase with cobaltic fluoride. The perfluorocarbons obtained revealed varying degrees of skeletal rearrangements. Thus, cycloheptane gave perfluoro-cycloheptane and -methylcyclohexane; cyclooctane gave at least eight fluorocarbons including-bicyclo(3,3,0)octane and -cyclooctane; cyclodecane gave a complex mixture from which were isolated perfluoro cis- and trans-bicyclo(4,4,0)decanes but no perfluorocyclodecane; cyclododecane and cyclooctadecane gave complex fluorocarbon mixtures in which none of the fluorocarbons with the original cycloalkene skeleton could be detected.Tetradecafluorobicyclo(3,3,0)octane gave dodecafluorobicyclo (3,3,0)oct-1(5)-ene and decafluorobicyclo(3,3,0)octa-di-1(5), 2-ene when pyrolysed over iron gauze.The fluorination of cyclooctane also afforded 1$\text{H}$-pentadecafluorocyclooctane which was dehydrofluorinated to tetradecafluorocyclooctene. This was converted to a range of derivatives including dodecafluorosuberic acid, 1,2-dichlorotetradecafluorocyclooctane, 1-methoxy tridecafluorocyclooctene and tetradecafluorocyclooctanone.     

Synthesis and intramolecular reactions of trans-cyclohexyl-1,2-bisacrylate

Photocycloaddition of dimethyl cyclobut-1-ene-1,2-dicarboxylate (1) with cyclohexene (7) afforded two photoadducts 8 and 9 in 44% and 28% yields, respectively. Spontaneous thermal isomerization of 8 gave (4Z,10Z)-dimethyl cyclodeca-4,10-diene-1,4-dicarboxylate (10), which subsequently isomerized to produce trans-1,2-cyclohexanebis-alpha-acrylic acid dimethyl ester 11. Hydride reduction of the bisacrylate 11 gave the trans-octahydro-1H-inden-2-ols 12a and 15 via a novel, stereoselective, intramolecular reaction. Reaction of the bisacrylate 11 with methyllithium afforded the bis-tertiary alcohol 16. In contrast, lithium dimethylcuprate reacted with the bisacrylate 11 to give the trans-hexahydro-1H-inden-2-one 17 in high yield via a novel, stereoselective, intramolecular reaction.