Reaktion von trans-1-arylbutadienen und 1,1-diarylbutadienen mit tetracyanethylen (TCNE) und 2,2-bis(trifluormethyl)ethylen-1,1-dicarbonitril (BTF): Präparative Studie

trans-1-Arylbutadienes $\text{5}$ yield normal DIELS-ALDER-adducts $\text{9}$ and $\text{10}$ with TCNE $\text{7}$ and BTF $\text{8}$. On the other hand 1,1-diarylbutadienes $\text{6}$ reacting with the same dienophiles give 1:1-adducts $\text{12}$/$\text{13}$ and/or $\text{14}$, respectively substitution products $\text{11}$. At higher temperature some vinylcyclobutanes $\text{12}$ undergo cycloreversion to $\text{15}$ and 1,1-dicyanoethylene.     

Syntheses of (1,1-dihydroperfluoroalkyl)aryliodonium triflates and their analogues

(1,l-Dihydroperfluoroalkyl)phenyl- and -$\text{p}$-fluorophenyliodonium triflates $\text{2}$ and $\text{3}$ were synthesized by the reaction of l-bis(trifluoroacetoxy)iodo-1,l-dihydroperfluoroalkanes $\text{1}$ with triflic acid and benzene or fluorobenzene in 1,1,2-trichlorotrifluoroethane. The use of fluorosulfonic acid and sulfuric acid instead of triflic acid afforded (1,l-dihydroperfluoroalkyl) phenyliodonium fluorosulfonate $\text{4}$ and sulfate $\text{5}$, respectively. Similarly, (1,1,ω-trihydroperfluoroalkyl)phenyliodonium triflate $\text{7}$ and 1,1,5,5-tetrahydroperfluoropentane-l,5-bisphenyliodonium triflate $\text{9}$ were synthesized.     

Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale

C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers $\text{2}$ to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses $\text{1}$ followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether $\text{2a}$ reacts with 2-acetoxy-3-keto-glycal derivative $\text{la}$ forming only one product $\text{3a}$. Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.     

Extraction of cobalt(II) and nickel(II) with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HPMBP) and tri-n-octylamine (TOA)

The extraction of Co(II) with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one ((H)PMBP) and tri-n-octylamine (TOA) is investigated in order to explore the influence of diluents and inorganic anions with synergistic acidic extractant + liquid anion exchanger systems. Although it is proved that the same species [HTOA]⁺ [Co(PMBP)₃]^? is extracted from various inorganic media, with toluene as the diluent, the presence of ClO₄^? SO₄^2? or Cl^? anion modifies the distribution of the anions which are associated to (HTOA)⁺ in the organic phase, leading to different synergistic equilibria; with Cl^? or SO₄^2?: $\text{CO(PMBP)}{}_2$ + $\text{(HTOA}{}^{\mathrm{+}}$,PMBP^?) ?$\text{(HTOA}{}^{\mathrm{+}}$,Co(PMBP)₃^? (log K = 6.10) and with ClO₄^? : $\text{Co(PMBP)}{}_2$ + $\text{HPMBP}$ + $\text{(HTOA}{}^{\mathrm{+}}$,ClO₄^? ? $\text{(HTOA}{}^{\mathrm{+}}$,Co(PMBP)₃^? + H⁺ + ClO₄^? (log K = 2.34) The same synergistic equilibrium is observed for the extraction of Ni(II) from ClO₄^? medium, with a comparable value of the constant (log K = 2.45). The synergistic effect is cancelled in n-octanol.     

Perhalogenmethylmercapto-heterocyclen,IX (perchlormethylmercapto)- und (perfluormethylmercapto)pyridine

Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride ($\text{1a}$) and 2-(trichloromethylmercapto)pyridine ($\text{1b}$). Neither a direct reaction of pyridine with CF₃SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF₃S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF₃)₂ yield 1:1-adducts ($\text{2a-d}$) only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF₃SCl to give 3-(trifluoromethylmercapto)pyridine ($\text{3}$); in addition a disubstituted product can be identified massspectroscopically. ¹H- and ¹⁹F-NMR-spectra are reported.     

Platinum(0) complexes of 3-arylthiete 1,1-dioxides

3-Phenyl- and 3-p-bromophenyl-thiete 1,1-dioxides react with [Pt(trans-stilbene)(PPh₃)₂] and [Pt(AsPh₃)₄] to give the complexes [Pt($\text{CHCrCH}{}_2\text{S}$O₂)(MPh₃)₂] (R  Ph, p-BrC₆H₄; M P, As).     

Intramolecular Lewis-acid promoted (2+2) cycloadditions: An efficient total synthesis of (±)-coronafacic acid via an internal Diels-Alder reaction.

Internal (2+2) cycloaddition of the ester $\text{7}$ gave the cyclobutene $\text{8}$ in fair yield; cyclization of the readily derived trienone $\text{4}$ and hydrolysis produced coronafacic acid in 7% overall yield.     

Stereoselektive synthese von α-glucosiden mit 1,1′ -diacetal-struktur

Reaction of ($\text{1b}$) and ($\text{1d}$) with the acetal ($\text{2a}$) in presence of trimethylsilyl trifluoromethanesulfonate at ?70° C gives the α-glucosides ($\text{3a}$) and ($\text{4a}$), whereas ($\text{1a}$) and ($\text{1c}$) lead to the β-glucosides ($\text{4c}$) and ($\text{4b}$). At 0° C reaction of ($\text{1a}$) with the acetals ($\text{2b-g}$) gives exclusively the α-glucosides ($\text{3b-g}$).     

New 1,1-amino hydroperoxides from regioselective oxygenation of 4-(n-arylmethyleneamino)-2,6-di-t-butylphenols.

The oxygenation of 4-(N-arylmethyleneamino)-2,6-di-$\text{t}$-butylphenols with Co(Salpr), a five coordinate Co(II0 Schiff base complex, in CH₂Cl₂ results in the regioselective hydroperoxylation at the imino carbon to give N-(l-aryl-l-hydroperoxymethyl)-3,5-di-$\text{t}$-butyl-$\text{p}$-benzoquinone monoimines, which give exclusively the corresponding amides and 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone in an aerobic solution of KOH in 90% EtOH.     

Die konstitution der fungistatischen ansamycin-antibiotica ansatrienin A und B

The structure of ansatrienin A ($\text{1}$) and B ($\text{6}$) is assigned by spin decoupling experiments and chemical reactions. The ansatrienins are unique members among the ansamycin-antibiotics because of their substituent pattern in the ansa bridge.     

(4+2)-cycloaddition of nitroalkenes with ynamines; formation of a 4H-1,2-oxazine 2-oxide derivative

The formation of a thermally unstable (4+2)-cycloadduct, a 4H-1,2-oxazine 2-oxide derivative ($\text{1}$), from the reaction of 1-nitrocyclopentene with 1-phenyl-2-(1-pyrrolidinyl)acetylene has been proven by the structure elucidation of isoxazole derivative $\text{3}$ which results from thermal rearrangement and by the structure determination of the 1,3-dipolar adducts $\text{5}$ of $\text{1}$ with electron-deficient acetylenes.     

A reversible claisen rearrangement of 3-(3,3-dimethylallyl)-4-(3,3-dimethylallyloxy)quinolin-2-one; synthesis of buchapsine and loss of its 1,1-dimethylallyl group

Reversible Claisen rearrangement of 3-(3,3-dimethylallyl)-4-(3,3-dimethylallyloxy)quinolin-2-one ($\text{5}$) furnished the alkaloid, buchapsine ($\text{6}$), which readily lost the 1,1-dimethylallyl group; a mechanism for the cleavage reaction is proposed.     

(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes as (E)-1-(1,3-butadienyl) synthons

(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes (E/Z=9), prepared from 4-trimethylsilyl-1-buten-3-ol, $\text{n}$-butyllithium and benzenesulfenyl chloride and oxidation of the intermediate (E)- and (Z)-1-benzenesulfinyl-4-trimethylsilyl-2-butenes with hydrogen peroxide, react with $\text{n}$-butyllithium and then primary halides to give 4-benzenesulfonyl-1-trimethylsilyl-2-alkenes which are rapidly 1,4-debenzenesulfonyltrimethylsilated to (E)-1,3-alkadienes by tetra-$\text{n}$-butylammonium fluoride at O°C.     

Organothallium compounds XII NMR spectra of some polyfluorophenylthallium (III) compounds

The PMR and ¹⁹F NMR spectra of the complexes R₂TlBr (R = C₆F₅, $\text{o}$-HC₆F₄, $\text{m}$-HC₆F₄, 3,5-H₂C₆F₃, or 3,6-H₂C₆F₃ and R₃Tl(diox) (R = C₆F₅, $\text{m}$-HC₆F₄, or 3,5-H₂C₆F₃; diox = 1,4-dioxan) have been recorded. Proton and fluorine chemical shifts, thallium-proton, thallium-fluorine, fluorine-fluorine, and fluorine-proton coupling constants, and thallium substituent chemical shifts are given and discussed     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Darstellung und reaktionen von 1,3-bis-(trimethylsiloxy)-isobenzofuranen

1,3-Bis-(trimethylsiloxy)-isobenzofuran ($\text{2a}$) can be prepared from dihydro phthalic anhydride. It is not stable under the reaction conditions but can be trapped with dienophiles. The tetraphenyl derivative $\text{2b}$ showed to be more stable towards protonation.     

Introduction of one-carbon units during anthraquinone-catalysed pulping of wood

Anthraquinone- and tetrahydroanthraquinone-catalysed pulping of $\text{Pinus}$$\text{radiata}$ has given 10-methyl-9-anthrone (2) and derivatives (3) and (4), introduction of the carbon substituent involving carbohydrate constituents of the wood.     

Substituent effects on fluorine - 19 chemical shifts in benzobicyclo(2.2.2)octen-1-yl fluorides

Inverse ¹⁹F substituent chemical shifts (SCS) of $\text{m}$- and $\text{p}$-substituted benzylfluorides are shown to have their origin in hyperconjugation involving the CF δ - bond.     

Einfache und stereoselektive synthese von α- und β-phenylglykosiden

Reaction of phenyl-trimethylsilylethers ($\text{3}$) with 1-O-trimethylsilyl-2,3,4,6-tetra-O-acetyl-D-glucoside ($\text{1}$) (anomeric mixture) yields almost exclusively the aryl-β-glucosides ($\text{4}$) in the presence of catalytic amounts of TMS-triflate at 20°C, whereas ($\text{3}$) and 1-O-trimethylsilyl-2,3,4,6-tetra-O-benzyl-D-glucoside ($\text{2}$) gives mainly the aryl-α-glucosides ($\text{8}$).     

Reactions of triphenylarsine oxide with aqueous hydrogen fluoride: Crystal structure of bis(triphenylarsine oxide)hydrogen(I) tetrafluoroborate

Fluorination of triphenylarsine oxide by aqueous hydrogen fluoride (1–40%) in the absence of glass readily gives triphenylarsine difluoride. When the reaction with dilute (1%) aqueous hydrogen fluoride is carried out in borosilicate glass apparatus, the glass participates in the reaction resulting in the formation of the crystalline 2:1 adduct 2Ph₃AsO·HBF₄. Crystals of this compound are monoclinic, $\text{P}$2₁/$\text{c}$, $\text{a}$ = 12.926(4), $\text{b}$ = 17.819(6), $\text{c}$ = 14.994(4) Å, β = 98.97(3)°, Z = 4. The structure contains cations [(Ph₃AsO)₂H]⁺ in which $\text{O}\text{?}$O is 2.44(2)Å, and anions BF₄^?.