N-halogeno-compounds. Part 9 [1]. Azoxy- and azo-arenes derived from 4-(dichloroamino)tetrafluoropyridine; crystal structure of trans-2,3,5,6-tetrafluoro-4-(2,4,6-trimethylphenyl-onn-azoxy)pyridine

The nitrosoarenes ArNO (Ar = C₆H₅, 2-MeC₆H₄, 2,4,6- Me₃C₆H₂ and C₆F₅) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds py_FN$\text{N}\text{+}$($\text{N}\text{-}$)Ar (py_F = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of py_FNNC₆H₂Me₃-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆F₅. X-Ray methods have been used to determine the molecular geometry of py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆H₂Me₃-2,4,6.     

Short synthesis of 6-oxoprostaglandin E1 and 6-oxoprostaglandin F1α

6-Oxoprostaglandin E₁ methyl ester was synthesized in a single pot from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by organocopper conjugate addition with an ω side-chain unit, trapping of the resulting enolate with 6-methoxycarbonyl-2-nitrohex-1-ene, and treatment with aqueous titanium(III) trichloride. Hydrolysis of the methyl ester was accomplished by porcine liver esterase. 6-Oxoprostaglandin F_1α, was obtained from 6-nitroprostaglandin E₁ methyl ester in four steps.     

A short and efficient synthesis of 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones

The cycloaddition of α,β-epoxyaldehydes or ketones ($\text{2}$) with the ketene acetal MeHC=C(OMe)₂ ($\text{1}$) gives epoxyoxetanes ($\text{3}$) in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones ($\text{6}$) via the epoxy esters $\text{4}$ and trihydroxy esters ($\text{5}$). The lactones $\text{6}$ appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones ($\text{7}$) and 3-methyl-5-ylidene-2-5H-furanones ($\text{8}$)     

Organomercury compounds XX Reactions of lithium polyfluorobenzenesulphinates with mercuric salts

The lithium polyfluorobenzenesulphinates, Li O₂SR (R = C₆F₅, $\text{p}$-HC₆F₄, $\text{m}$-HC₆F₄, or $\text{o}$-HC₆F₄), and the dilithium tetrafluorobenzenedisulphinates, $\text{p}$- and $\text{o}$-(LiO₂S)₂C₆F₄, have been prepared by reaction of the appropriate polyfluoroaryllithium compounds with sulphur dioxide. All compounds were isolated as hydrates and gave the corresponding $\text{S}$-benzylthiouronium salts on treatment with $\text{S}$-benzylthiouronium chloride. From reactions of the lithium sulphinates with suitable mercuric salts in water, generally at room temperature, the derivatives RHgX (R = C₆F₅, X = Cl, Br, CH₃CO₂, or PhSO₂; R = $\text{p}$-HC₆F₄, X = Cl, Br, or CH₃CO₂; R = $\text{m}$-HC₆F₄, X = Cl or Br; R = $\text{o}$-HC₆F₄, X = Cl), $\text{p}$-(XHg)₂C₆F₄ (X = Cl, Br, or CH₃CO₂), and $\text{o}$-(XHg)₂C₆X₄ (X = Cl or Br) have been prepared. Similarly, the bispolyfluorophenylmercurials R₂Hg (R = C₆F₅, $\text{p}$-HC₆F₄, or $\text{m}$-HC₆F₄) have been prepared from the corresponding lithium sulphinates and either mercuric salts or polyfluorophenylmercuric halides in aqueous $\text{t}$-butanol. A possible mechanism for the sulphur dioxide elimination reactions is discussed.     

5-Exo-Trig vs 6-Endo-Trig α-acyliminium ion-olefin cyclisations stereoselective synthesis of 7-(1-formyloxy-pent-1-yl)-1-aza-4-oxa-spiro[4.5]decane-2-ones

The two C₆, C₇$\text{trans}$ substituted title compounds have been synthesized via stereoselective 5-$\text{Exo}$-Trig ringclosures starting from (E)-resp. (Z)-4-nonene-1-yl bromide and 3,5-morpholinedione.     

The effect of environment on the reactions of thiiranium ions

The thiiranium ion formed by the reaction of $\text{Z}$-1-phenylpropene and (4-ClC₆H₄S)₂SC₆H₄ClSbCl₆ in CH₂Cl₉ at ?70°C reacts with Cl^? to form both $\text{erythro}$- and $\text{threo}$-Markownikoff B-chlorosulfides.     

From penicillin to penem and carbapenem. VI1) : Synthesis of dethiathienamycin

A new C₃-unit substitution reaction at C-4 position of 4- acetoxyazetidinone derivative ($\text{1}$ and $\text{5}$) by tetraallyltin ($\text{2}$) in the presence of 1/10 eq. of BF₃-ether in methylene chloride is described. From 4-allylazetidinone derivative ($\text{3}$) via ylid intermediate ($\text{14}$) dethiathienamycin ($\text{16}$) was synthesized.     

Proton and carbon nuclear magnetic resonance study on some n- and o-acyl derivatives of monohydroxypyridines

Comparative study on the proton and carbon NMR spectra for a series of $\text{N}$- and $\text{O}$-acyl substituted monohydroxypyridines (C₅H₄NO$\text{R}$: $\text{R}$=-H, -CHO, -COCH₃, -COC(CH₃)₃, -COCF₃, -COC₆H₅, -SO₂CH₃, -SO₂C₆H₄CH₃ is reported. p]Characteristic ¹H, ¹³ NMR and IR spectral features allow simple and unambiguous distinction between the isomeric $\text{N}$- and/or $\text{O}$-acyl-derivatives of 2-, 3- and 4-hydroxypyridines, so that both forms can clearly be identified when tautomeric equilibria occur, since the tautomerism rate is slow on the NMR time scale     

A novel synthesis of carbacyclin analogs via a stereoselective introduction of 15α-hydroxy group

(+/-)-6,9α-Methanoprostaglandin I₃, ($\text{2}$) and (+/-)-5,6-dihydro-6,9α-methano-6β-prostaglandin I₃, ($\text{4a}$) have been synthesized using a new method for the stereoselective introduction of the 15α-hydroxy group via a stereoselective electrophilic addition of phenyl-sulfenyl chloride to the enol ether ($\text{6}$) and ($\text{23}$) respectively.     

3-Bromo-2-(tert-butylsulfonyl)-1-propene. A multi-coupling reagent Part 1.

3-Bromo-2-(tert-butylsulfonyl)-1-propene $\text{4}$ is easily available in two steps from allyl-tert-butylthioether $\text{5}$ (70% overall yield). It reacts with a great variety of carbanions to give functionnalized α, β-unsaturated sulfones of type $\text{7}$ in high yields. A second nucleophile (lithium cuprates) can then be added to compounds $\text{7}$ to furnish functionnalized sulfones of type $\text{3}$ (Y=SO₂-tert-butyl).     

Methylated multibridged [2n]cyclophanes. All alternate synthesis of [26](1,2,3,4,5,6) cyclophane (superphane)

A sequence of formylation followed by a carbene insertion reaction has led to the stepwise introduction of additional ethano bridges into 4,5,7,8- tetramethyl [2₂](1,4)cyclophane ($\text{1}$), providing syntheses of 5,7,8-trimethyl- [2₃](l,2,4)cyclophane ($\text{6}$), a mixture of 5,8-dimethyl[2₄(1,2,4,5)cyclophane ($\text{10}$) and 5,7-dimethyl[2₄(1,2,3,5)cyclophane ($\text{11}$, and-4-methyl[2₅](1,2,3,4,5)-cyclophane ($\text{14}$). This route to $\text{14}$ completes a formal eight-step synthesis of [2₆](1,2,3,4,5,6)cyclophane ($\text{15}$, superphane) with an overall yield of 17%. A Birch reduction of $\text{6}$ readily gave 12,15-dihydro-5,7,8-trimethyl[2₃](1,2,4)-cyclophane ($\text{7}$) in 85% yield.     

Sulphur substituted organotin compounds. Part 6. Reactions of mercaptomethyltin compounds with arenesulphenyl chlorides

Reactions between Ph₃SnCH₂SAr and 2-NO₂C₆H₄SC? lead to the formation of 2-(ArSCH₂-6-NO₂C₆H₃SSC₆H₄NO₂-2 via the [2,3]sigmatropic rearrangement of the S-arylthio-sulphonium ylides $\text{C}$H₂$\text{S}\text{+}$(Ar)SC₆H₄NO₂2.     

Some reactions of copper(I) pentafluorothiophenolate as a nucleophile

Several aromatic compounds containing one or two C₆F₅S groups have been prepared by nucleophilic displacement reactions using CuSC₆F₅ in DMF solution. Aromatic iodine or bromine, rather than chlorine of fluorine is replaced by the SC₆F₅ group using CuSC₆F₅. A mechanism is postulated. New compounds prepared include $\text{p}$-(C₆F₆F₅S)₂C₆H₄, $\text{o}$- and $\text{m}$-(C₆F₅S)₂C₆F₄ and $\text{p}$XC₆H₄SC₆F₅(X=C1, NO₂, I, CH₃, CO₂C₂H₅).     

Cis-trihetero-tris-σ-homobenzenes as tridentate ligands - X-ray crystal. Structure analyses of the Co(C6H9N3)2(NO3)3 and Ba(C6H6O3)4(ClO4)2-complexes

According to X-ray crystal structure analyses “cis-benzenetrisimine” ($\text{2}$) and “cis-benzenetrioxide” ($\text{1}$) act as tridentate ligands in their 2:1- and 4:1-complexes $\text{7}$ (Co(C₆H₉N₃)₂(NO₃)₃) and $\text{8}$ (Ba(C₆H₆O₃)₄(ClO₄)₂), resp. The latter is the rare example of an organic complex with the (approximate) T-symmetry.     

Conformation,in solution,of c-4-t-butyl-1-phenyl-r-1-(N-piperidyl)cyclohexane hydrochloride. The conformational energy of t-butyl

Although the hydrochloride of $\text{c}$-4-$\text{t}$-butyl-1-phenyl-$\text{c}$-1-(N-piperidyl)cyclohexane crystallizes in the conformation with axial $\text{t}$-butyl, it exists as an almost equimolar mixture of the two chair conformers in CD₂ Cl₂ solution. The position of equilibrium allows one to calculate ΔG°_{$\text{t}$-Bu} as ?4.9 kcal/mol.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

Cycloaddition of single oxygen and triazolinedione (TAD) with spirocyclopentadienyl-1,3,5-cycloheptatrienes1: tropilidene versus norcaradiene reactivity

4-Methyl-1,2,4-triazoline-3,5-dione (MTAD) gives with 7-spiro-fluorenyl-1,3,5-cycloheptatriene ($\text{1d}$) initially he norcaradine-type urazole ($\text{N3d}$) which at ambient temperatures rearranges into ($\text{6d}$), while ¹0₂ gives the tropilidene-type endoperoxide ($\text{T4d}$).     

Biosynthesis of psilotin from [2′,3′-13C2,1′-14C,4-3H]phenylalanine studied with 13C-NMR

The 6-phenyl-dihydro-α-pyrone moiety of psilotin is formed from [2′,3′-¹³C₂,1′-¹⁴C,-4-³H]phenylalanine in the plant $\text{Psilotum}$$\text{nudum}$ with retention of all the isotopes.     

A stereocontrolled partial synthesis of 1α-hydroxy vitamin D3

A novel and efficient partial synthesis of 1α-hydroxy vitamin D₃ ($\text{6}$), starting from 7-dehydrocholesterol ($\text{1}$), is reported. The crucial step in the synthesis involves a selective Diels-Alder reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with the 6,8-diene system of previtamin D₃ ($\text{3}$), generating an adduct $\text{7}$ suitable for the stereoselective introduction of the 1α-hydroxyl group. Cycloreversion of $\text{13}$ leads to the title compound.     

A general synthesis of primary prostaglandins

Combination of ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone, ($\text{S}$)-($\text{E}$)-3-$\text{t}$-butyldimethylsiloxy-1-iodo-1-octene, and 6-methoxycarbonyl-2-hexynal via the tandem organo-copper conjugate addition—aldol reaction procedure leads directly to a 5,6-dehydroprostaglandin E₂ derivative, which can be transformed to a variety of chiral primary prostaglandins in a stereoselective manner.