Stereospecific synthesis of (5E)-PGE2 by palladium-catalyzed decarboxylative 2-alkenylation of 2-alkenyloxycarbonylated cyclopentanone derivative

(5$\text{E}$)-Prostaglandin E₂ methyl ester was synthesized from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by $\text{in}$$\text{situ}$ 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ($\text{E}$)-2-butenylated cyclopentanone derivative was obtained from either 2-[($\text{E}$)- or ($\text{Z}$)-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition.     

Fluorocarbon derivatives of nitrogen. Part 11. Synthesis of some 2-(trifluoromethyl)imidazo[1,2-a]pyridines from trifluoroacetonitrile

3-(t-Butoxycarbonyl)-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine, prepared from trifluoroacetonitrile and pyridinium t-butoxycarbonylmethylide, reacts smoothly with trifluoroacetic acid to provide 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine-3-carboxylic acid, which gives 2-(trifluoromethyl)imidazo[1,2-$\text{a}$]-pyridine when heated. 3-Cyano-2-(trifluoromethyl)imidazo[1,2-$\text{a}$]pyridine can be obtained $\text{via}$ treatment of trifluoroacetonitrile with pyridinium cyanomethylide, which is sufficiently reactive to effect nucleophilic displacement of fluorine from pentafluoropyridine under mild conditions [→pyridinium cyano(tetrafluoro-4-pyridyl)methylide].     

A synthetic approach to (+)-aldosterone and its relatives (2)- a stereoselective synthesis of (+)-trans-4,5-(4-methoxybenzo)- 1β , 7aβ - ( 2α-methoxymethyl- 5 -oxofuro) hydrindane

A stereoselectivity in an intramolecular cycloaddition of the olefinic $\text{o}$-quinodimethanes 13 and 23 generated $\text{in}$$\text{situ}$ from the thermolysis of optically active 4β-[2-(4-methoxybenzocyclobutenyl)ethyl] -5α-methoxymethyl-3-phenyl-thio-methylenefuran-2-ones 12 and 22, respectively, is studied and a stereoselective synthesis of (+)-$\text{trans}$-4,5-( 4-methoxybenzo) -1β,7aβ-(2α-methoxymethyl-5-oxofuro)hydrindane 1 is also described.     

Studies in azide chemistry. Part 12. One-pot conversion of 4-azidotetrafluoropyridine to 1,3,4-trifluoro-7,9-dimethyl-11H-pyrido[4,3-c]benzo[1,2]diazepine

Thermolysis of 4-azidotetrafluoropyridine in the presence of an excess of mesidine at 170 °C yields tetrafluoro-4-(2,4,6-trimethylphenylazo)- pyridine, which undergoes intramolecular dehydrofluorination $\text{in situ}$ to provide 1,3,4-trifluoro-7,9-dimethyl-11$\text{H}$-pyrido[4,3-$\text{c}$]benzo[1,2]diazepine.     

Amino-sulphur-fluorine derivatives as fluoride ion donors: preparation of three- and four-coordinated cations of sulphur (IV) and (VI) [1,2]

Pentacoordinated aminosulphur (IV) trifluorides, R₂N$\text{S}$F₃, (in this paper the lone pair in S(IV)-derivatives is always considered as a ligand) and aminosulphur(VI)-oxidetrifluorides, R₂NS(O)F₃, readily lose a fluoride ion to Lewis acids (AsF₅, SbF₅, BF₃) to give sulphur-containing cationic species [R₂N$\text{S}$F₂]⁺ and [R₂NS(O)F₂]⁺ with tetracoordinated sulphur. Tetracoordinated neutral dialkylaminosulphur(IV)-oxidefluorides, R₂N$\text{S}$(O)F, and amino-imino sulphur(IV)fluorides, R₂N$\text{S}$(=NR_f)F, give three-coordinated sulphur cations [R₂N$\text{S}$O]⁺] or [R₂N$\text{S}$NR_f]⁺.The three-coordinated sulphur(VI)cation [R₂NS(O)NR]₊ has also been formed.     

Efficient separation and recovery of V(V) from Cr(VI) in aqueous solution using new task-specific ionic liquid of [C12H25NH3][Cyanex 272]

An environmentally friendly process for efficient separation and recovery of V(V) from aqueous solution containing Cr(VI) was proposed using the new task-specific ionic liquid of [C₁₂H₂₅NH₃][Cyanex 272]. The separation factor of V(V) from Cr(VI) was about 1.08 × 10³ with the optimum extraction conditions, and the extraction percentage of V(V) was about 99.5 %. The loaded organic phase was stripped using the NH₃·H₂O, and the recovered NH₄VO₃ was obtained with the processes of stripping, filtration, washing, and desiccation. The qualitative analysis of the recovered NH₄VO₃ was made using the X-ray diffraction, and its peaks were good consistent with the standard sample. Morphology of the recovered NH₄VO₃ was also studied using the scanning electron microscope. The extraction mechanism of V(V) using the [C₁₂H₂₅NH₃][Cyanex 272] was investigated using the slope method and infrared spectrum analysis. This new environmentally friendly process can be used for the separation and recovery of V(V) from real leaching solution with the aim of industrial application.     

Some reactions of 1,2,3,4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene: Thermolysis and attack by methoxide ion and by bistrifluoromethyl nitroxide

1,2,3,4,7,7-Hexafluorobicyclo[2,2,1]hepta-2,5-diene gave 1,2,3,4-tetrafluorebenzene in at least 73% yield when heated to 450°C in a sealed tube; the CF₂ bridge appeared, in part, as octafluorocyclobutane. Nucleophilic attack by sodium methoxide- methanol on the diene occurred exclusively at the CFCF bond, causing the formation of 1,2,4,7,7-pentafluoro-3-methoxybicyclo- [2,2,1]hepta-2,5-diene and a 1,4,5,6,7,7-hexafluoro-5-methoxybicyclo [2,2,1]hept-2-ene thought, on the basis of ¹⁹F nmr data, to be the 6-$\text{endo}$-F,5-$\text{exo}$-MeO isomer. Radical attack on 1,2,3,- 4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene by bistrifluoromethyl nitroxide took place at both olefinic sites, with a $\text{ca}$. 10:1 preference for the CFCF linkage; all three geometrical isomers of 5,6-bis(bistrifluoromethylamino-oxy)-1,4,5,6,7,7- hexafluorobicyclo[2,2,1]hept-2-ene were formed.     

Nuclear magnetic resonance spectra of polyfluorobuta-1,3-dienes. Part II [1]. Variable temperature study of two 2-azabutadienes

The two perfluoro-azadienes CF₂N.CRCF₂ (R = CF₃ or CF₂Cl) show temperature dependent ¹⁹F n.m.r. spectra, with non-equivalent fluorine nuclei of the CF₂N portion at low temperatures, which coalesce due to inversion at the nitrogen at higher temperatures (ΔG3 = 60 kJ mol^?1). N.m.r. parameters have been obtained. One of the five-bond FF coupling constants is much larger ($\text{ca}$. 24 Hz) than the remainder (0·5–5·5 Hz), possibly due to ‘through-space’ coupling of fluorines in the $\text{cis}$-skew conformation.     

Fluorocarbon derivatives of nitrogen. Part VII [1]. Reaction of N-iminopyridinium ylide with perfluoro-1-azacyclohexene,perfluoro-2-azapropene,and perfluoroacetonitrile

The novel ylides (II) and (III) have been obtained $\text{via}$ treatment of perfluoro-1-azacyclohexene and perfluoro-2-azapropene, respectively, with $\text{N}$-iminopyridinium ylide (I) generated $\text{in}$$\text{situ}$ from $\text{N}$-aminopyridinium iodide and anhydrous potassium carbonate in methylene chloride. A mixture of the $\text{s}$-triazolo[1,5-$\text{a}$]pyridine (IV) and a compound thought to be its dihydro-analogue (V) were isolated following attack on perfluoroacetonitrile by the parent ylide (I); the former product was also prepared by heating 1,2-diamino-pyridinium iodide with trifluoroacetic anhydride.     

The biosynthesis of pentalenolactone

Feeding of [UL-¹³C₆]-glucose, an $\text{in}$$\text{vivo}$ precursor of [1,2-¹³C₂]-acetyl-CoA, gave pentalenolactone in which the pattern of ¹³C-enrichments and couplings supported a mevalonoid biosynthetic pathway.     

Mechanism of campesterol demethylation in insect

[24-²H]-, [25-²H]-, and [23,23,25-²H₃]-24ξ-methylcholesterol as well as [23,23,25-²H₃]-24-methylenecholesterol were metabolized in the silkworm $\text{Bombyx}$$\text{mori}$ to cholesterol containing zero, one, three and three deuterim, respectively.     

H3N·PF5 and H2NPF5−, new compounds in the system H3N/PF5

Phosphorus pentafluoride was reported long ago to give adducts 2 PF₅ ·5 NH₃ (1) and nNH₃·PF₅ (n= 1 ? 4) (2). None of the compounds was characterised in detail. Repeating the reaction of PF₅ and NH₃ we found the adduct H₃N·PF₅, $\text{1}$, in 8% yield besides (H₂N) ₂PF₃ (3) and NH₄PF₆. However, HF and (F₂P=N)₃ gave $\text{1}$ in 41% yield. The ¹H, ¹⁹F, and ³¹P n.m.r. spectra of $\text{1}$ exhibit ¹⁴NH, ¹⁴NPF(cis), and ¹⁴NP coupling. The x-ray structure determination shows almost perfect octahedral geometry at phosphorus with a PN bond length of 1.842 ā. Compound $\text{1}$ is soluble in water without decomposition. Treatment with NH₃ leads to the anion H₂NPF₅^?. Upon heating $\text{1}$ forms in good yield H₂NPF₄ and NH₄PF₆. Without a solvent $\text{1}$ and NH₃ react to give (H₂N) ₂PF₃. A mechanism for the ammonolysis of PF₅ is proposed.     

Addition and cycloaddition reactions of allenyl cations with various cycloalka-1,3-dienes

Allenyl cations

, generated $\text{in}$$\text{situ}$ from propargyl chlorides and zinc chloride give monocyclic adducts or [3+4] and [2+4] cycloaddition products with various cycloalka-1,3-dienes. The mode of addition depends on R and the ring size of the 1,3-dienes.     

Photoaddition reactions of trans dichloroethylene with benzenoid compounds: facile formation of tetracyclo[3.3.0.02,804,6]octanes and semibullvalenes

$\text{trans}$ 1,2-Dichloroethylene undergoes a stereospecific photoreaction with benzonitrile, the three tolunitriles, α,α,α-trifluorotoluene, fluorobenzene, and chlorobenzene to give substituted 6-$\text{exo}$ 7-$\text{endo}$ dichlorotricyclo[3,3,0,0_2,8]oct-3-enes which on treatment with base yield cyclised products or semibullvalenes: phenol yields dichlorobicyclo[3.2.1]oct-2-en-8-one with this ethylene photochemically.     

Investigations on the influence of charge density on the mutual deactivation of polyion-macroradicals—II

Bimolecular rate constants (2 k_R) of the reaction R· + R· in aqueous solution were measured using the pulse radiolysis technique. R· designates radicals produced by H atom abstraction from polyvinyl alcohol partially acetalyzed with glyoxylic acid. Due to the expansion of the coils, 2 k_R increases with X_i the content of ionized base units in mole %. Above a critical value x_i (crit), 2 k_R decreases due to intermolecular repulsion. x_i(crit) decreases with increasing chain length $\text{n}{}_{\mathrm{<mtext>n</mtext>}}$ [x_i (crit) ≈ 0·5 mole % at $\text{n}{}_{\mathrm{<mtext>n</mtext>}}\text{= 3000}$ and x_i (crit) ≈ 1·5 mole % at $\text{n}{}_{\mathrm{n}}\text{= 270}$]. In the presence of NaClO₄, the following salt effects were observed: for x_i >x_i (crit), 2 k_R is increased because the intermolecular repulsion is partially depressed by screening. Below x_i (crit), 2 k_R is decreased since the coil expansion is diminished. At very low values of x_i where the coil expansion due to intramolecular repulsion is negligible, no salt effect was detectable.     

Biosynthesis of citreothiolactone,citreopyrone and pyrenocine B

¹³C NMR spectroscopy using INADEQUATE pulse sequence method has been used to deduce the labelling patterns of the three metabolites of $\text{Penicillium citreo-viride}$ B. derived from [1,2-¹³C]acetate, indicating that their carbon skeletons consist of two different units [CH₃COCH₂COCH₂COS-Enzyme and CH₃COCH₂COS-Enzyme].     

New fluoride ion-catalyzed reaction of f-alkylacetylenes with silyl enol ethers. An efficient route to f-alkyl-substituted propargylic alcohols and α-hydroxy ketones

Treatment of $\text{F}$-alkylacetylenes, generated $\text{in}$$\text{situ}$ from 1$\text{H}$-$\text{F}$-1- alkenephosphonates, with silyl enol ethers in the presence of a catalytic amount of tetrabutylammonium fluoride gives good yields of $\text{F}$-alkyl-substituted propargyl alcohols or 4-(1$\text{H}$-$\text{F}$-alkylidene)-1,3-dioxolane derivatives, the latter being converted to tie corresponding α-hydroxy ketones.     

Synthesis of vicinal bromo-fluoro organic compounds using elemental fluorine

The direct action of fluorine on bromine at ?78° produces BrF which, without any isolation or purification, adds readily across various double bonds providing there is some hydrogen donor in the reaction mixture. Only trans addition of the elements of BrF was observed. When the reaction was applied to enons an easy elimination of HF can take place thus producing α-bromo enons.In our previous work we described the reaction of some olefins with IF, a reagent which was prepared $\text{in}$$\text{situ}$ by the action of F₂ on I₂[1]. The literature deals with several other fluorohalogens, among them the three known bromo-fluoro compounds, BrF, BrF₃ and BrF₅, although only the last two are well characterized[2]. However, because of the instability and the high reactivity of these compounds, they have hardly been employed in organic chemistry[3].We wish to describe here for the first time, an efficient and convenient method of synthesizing vicinal bromo-fluoro compounds using the primary source of the fluorine atoms, namely elemental fluorine itself[4].When a mixture of F₂/N₂ is bubbled through a cold (?78°C), dilute solution of Br₂ (20 mmolar) in CFCl₃ (Freon) the bromine disappears and mainly BrF is produced. However, despite previous efforts, it seems that this compound cannot be isolated since it disproportionates easily to the very reactive BrF₃ and halogen on the aromatic ring can not be ascertained. The third product proved to be the corresponding bromo-ethoxy compound XV (15% yield). Prolonged chromatography or traces of HF from the reaction mixture results in the elimination of HF thus producing, quantitatively, 6-bromocumarin XVI[8]. 2-Bromo-3-fluoro cyclopentanone XVII (oil) if formed in 90% yield and isolated in almost pure form. As in the case of cumarin, XVII readily loses HF producing the 2-bromoclopentenone (XVIII)[9] in quantitative yield.     

Biosynthesis of highly modified meroterpenoids in aspergillus variecolor. Incorporation of 13C-labelled acetates and methionine into anditomin and andilesin C

Incorporations of [1-¹³C]?, [2-¹³C]?, [1,2-¹³C₂]-acetates and [¹³C]-methionine into anditomin, a metabolite of $\text{Aspergillus variecolor}$, indicate its formation by a mixed polyketide-terpenoid biosynthetic pathway similar to that elucidated for andibenin; observations are made on the possible biosynthetic relationship of the $\text{A. variecolor}$ metabolites with austin and terretonin, mycotoxins recently isolated from $\text{A. ustus}$ and $\text{A. terreus}$ respectively.     

Boat-chair conformational preference of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

The ¹H and ¹³C nmr spectra of $\text{exo}$, $\text{exo}$-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d₆ or alkaline D₂O, clearly show that it exists in a $\text{boat}$-$\text{chair}$-conformation with $\text{equatorial}$ carboxyl groups, thus being the first case of $\text{boat}$-$\text{chair}$ preference of a bicyclo[3.3.1] nonan-9-one due to the presence of $\text{exo}$,$\text{exo}$-2,4- substituents.