Butyne photolysis

Gas-phase UV photolysis of tetrafluorodiphosphine in the presence of hexa-fluoro-2-butyne gives equal quantities of the products of syn and anti addition to the triple bond [21] (equation 15). 

In another study the kinetics and mechanism of an unprecedented T/2-vinyl isomerization of a highly fluorinated tungsten(II) metalla-cyclopropene complex was studied (92). Photolysis of a tungsten(II) tetrafluoroaryl metallacycle 1 and perfluoro-2-butyne results in the formation of the kinetic rf -vinyl complex 2 in which the fluoride is trans to the inserted acetylene and cis to both carbonyl ligands. Upon heating 2 is converted to the thermodynamic rf -vinyl complex 3 in which the fluoride ligand is now cis to the inserted alkyne and trans to one CO and cis to the second CO ligand as shown in Scheme 1. 

Photolytic. The major photolysis and hydrolysis products identified in distilled water were pentachlorocyclopentenone and hexachlorocyclopentenone. In mineralized water, the products identified include cis- and /ra/3s-pentachlorobutadiene, tetrachlorobutenyne, and pentachloro-pentadienoic acid (Chou and Griffin, 1983). In a similar experiment, irradiation of hexachlorocyclopentadiene in water by mercury-vapor lamps resulted in the formation of 2,3,4,4,5-pentachloro-2-cyclopentenone. This compound hydrolyzed partially to hexachloroindenone (Butz et ah, 1982). Other photodegradation products identified include hexachloro-2-cyclopentenone and hexachloro-3-cyclopentenone as major products. Secondary photodegradation products reported include pentachloro-as-2,4-pentadienoic acid, Z- and A-pentachlorobutadiene, and tetrachloro-butyne (Chou et ah, 1987). In natural surface waters, direct photolysis of hexachlorobutadiene via sunlight results in a half-life of 10.7 min (Wolfe et al, 1982). 

The direct photolysis of dimethyl diazomalonate in 2-butyne afforded the cyclopropene (276), but sensitization of the photolysis with benzophenone gave the furan (277) in 43% yield (Scheme 73) (71JA6337). Thermal rearrangement of 2,2-dimethoxycarbonylmethyl-enecyclopropane to 2-methoxy-3-methoxycarbonyl-4-methylfuran was observed, a reac-... 

There are also not very many data on the photolysis of 1,2,4-triazines. Many 1,2,4-triazines are not only stable to irradiation but they increase the photolytic stability of other systems. Meier tried to prepare trimethylazete (356) by matrix photolysis of trimethyl-1,2,4-triazine (355) but observed only the formation of 2-butyne, acetonitrile and nitrogen (80LA798). Photolysis of tris(heptafluoroisopropyl)-l,2,4-triazine (329) afforded tris(heptafluoroisopropyl)-l,3,5-triazine (357), nitrogen, perfluorobutyronitrile and bis(heptafluoroisopropyl)acetylene. The last three products are the same as in the pyrolysis of (329) <80JCS(P1)2254). 

Strong evidence for a thiirene intermediate in a photochemical reaction was gained by examining reaction products. Photolysis of either (15) or (16) in the presence of hexafluoro-2-butyne leads only to the thiophene (17 equation 7) (78JOC2487). 

Another route to neutral bisalkyne complexes is from the trifluoro-methylacyl precursor which deinserts carbon monoxide to yield trifluoro-methyl molybdenum products. Photolysis of CpMo(CO)3[C(0)CF3] in the presence of CF3C=CCF3 forms CpMo(CF3C=CCF3)2(CF3) CpMo-(DMAC)2CF3 is formed without photolysis (98). Addition of hexafluoro-butyne to CpMo(CO)(MeC=CMe)(CF3) forms the mixed bisalkyne via CO substitution. 

Replacement of the lone carbonyl ligand in [CpMo(RC=CR)2(CO)]-[BF4] was difficult, and no product was isolated from photolysis or heating of an acetonitrile solution of [CpMo(MeC=CMe)2(CO)][BF4]. Detection of free 2-butyne suggested that alkyne dissociation was occu-ring, and, indeed, isolation of [CpMo(MeC=CMe)2(MeCN)][BF4] with a labile acetonitrile ligand was accomplished once free MeC=CMe was added to the MeCN reaction solution prior to thermolysis (72). 

Pyridinium (trifluoroacetyl)methylide forms [3-1-2] cycloadducts with a wide variety of perfluorinated and partially fluorinated olefins, alkynes, and nitriles [86JFC(34)275]. Photolysis of a mixture of hexafluoro-3-diazobutan-2-one and perfluoro-2-butyne in the gas phase results in the formation of tetrakis(trifluoromethyl)furan a ketocarbene is the key intermediate of this reaction sequence (87JOC2680) (Scheme 79). 

The cycloadducts formed on reaction of hexafluoro-2-butyne and 2-substituted furans can be hydrogenated selectively at the unsubstituted carbon double bond. On flash thermolysis at 400°C, these products undergo retro-Diels-Alder reaction to give 3,4-bis(trifluoromethyl)-substi-tuted furans [91JFC(54)249]. A thermally stable [4-1-2] cycloadduct is obtained on heating hexafluoro-2-butyne and 3,4-bis(trifluoromethyl)-furan the retro reaction occurs on photolysis (92JHC113) (Scheme 90). 

Irradiation of [68] at room temperature results in low yields of acetylene, propyne, and butyne. Dimethyl-tetrahedrane is a speculative intermediate in this photolysis (63). 

The photochemical reaction between ozone and dimethylacetylene has been examined using both matrix isolation and ab initio methods <1999PSA7280>. The photolysis of hexafluoro-2-butyne and ozone forming oxirene... 

Numerous papers have been published describing the photochemical production of enones from carbonyl compounds and alkynes. The first detection of an oxetene intermediate involved low-temperature (-78 C) photolysis of 2-butyne and benzaldehyde to form the photoproduct (61), which was observed by NMR. The oxetene undergoes further photoreaction with benzaldehyde to form the novel fused oxetane (62). Recently, Friedrich has reported Either studies on the reactivity of oxetenes and developed alternative syntheses of the parent compound and 3-phenyloxete (64). The parent oxetene is found to have a thermal half-life of t proximately 8 h in solution at room temperature. The phenyl-substituted derivative (64) underwent slow ring-opening under acidic conditions to form 2-phenylprq)enal and air oxidation to yield a formate derivative, probably via a radical process. 

The first stable 1,2-dithiete, 3,4-bis(trifluoromethyl)-1,2-dithiete 527, was reported in 1960, as a result of the reaction of hexafluoro-2-butyne with boiling sulfurother fluorinated derivatives are prepared similarly.The strained acetylene 528 reacts with sulfur to give dithietes. Ring-contraction of 529 with loss of ethylene gives yellow needles of the benzo-1,2-dithiete 526. ° Benzo-dithiete (stable to 180°K) has been obtained by thermolysis of 529a-c or photolysis of 529a. The benzodithiete structure proposed for the product of the oxidation of o-benzenedithiol by iodine is incorrect the material is a polymer. " 3,4-Di-t-butyl-l,2-dithiete is obtained by spontaneous cyclization of the dithione valence tautomer. " ... 

CIDNP results have also been taken as evidence for the participation of different electronic states in the photolysis of acetylpropionyl peroxide,while the polarizations in the photoreaction of 3-ferf-butylperoxy-3-methyl-l-butyne were... 

Gas-phase photolysis of hexafluoro-3-diazo-2-butanone (266) in an excess of hexafluoro-2-butyne (267) yields the furan 268. 

Several methods for the syntheses of this type of furan derivatives are based on the usage of unsaturated aliphatic fluorine-containing compounds. Gas-phase photolysis of the mixture of diazoketone 70 and hexafluoro-2 butyne yields the tetrakis(tri-fluoromethyl)furan as main product.Ketocarbene intermediate 71 undergoes 1,3-addition to 2-butyne to give furan 72. 

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