Synthesis of “capped porphyrins”

The synthesis of “capped porphyrins” ($\text{10}$), ($\text{18}$), and ($\text{28}$), and their (chloro)iron(III), iron(II), cobalt (II), and zinc(II) complexes is reported. These complexes serve as models for the active site of the oxygen binding haemoproteins. In addition to reversible binding of dioxygen by each of the iron (II) porphyrin complexes, the 1-methyl-imidazole-(“C₃-capped porphyrin”) iron (II) complex ($\text{23}$) reacts reversibly with carbon monoxide, in solution at 25°C.     

Reaction of neorl with thallium(III) perchlorate

Reaction of nerol ($\text{1}$) with thallium(III) perchlorate gave 6-oxabicyclo[3.2.1]octane derivatives ($\text{2}$) and ($\text{3}$), and 6,9-dioxabicyclo[3.3.1]nonane derivatives ($\text{4a–d}$) as the cyclization products.     

Thallium(III) salt-induced olefinic cyclization of o-prenylphenols

Olefinic cyclization of $\text{o}$-prenylphenols ($\text{1}$), ($\text{4}$) and ($\text{6}$) induced by thallium(III) trifluoroacetate was performed.     

Bile pigment studies—III: Controlled oxidative degradation of 1,19(21,24h)-bilindiones (bilitrienes)

Treatment of the model 1,19(21,24$\text{H}$)-bilindione (1) with thallium(III) acetate in methanol gives the thallium(III) complex (11) which is unstable and in the presence of air and methanol is transformed into the 15,16-dimethoxy complex (12), characterised as the metal free derivative (13). When exposed to light, solutions of (12) are oxidised to afford, after work-up, the 14-formyl-1(15$\text{H}$)-tripyrrinone (4) and ethylmethylmaleimide (17). A general discussion of mechanistic implications is presented.     

Paramagnetische organothalliumverbindungen in lösung: I. Esr-untersuchungen von diphenyl-thallium(III)-tonenpaaren mit brenzcatefechinen,pyrogallolen und 1,2-diketonen

Diphenylthallium hydroxide reacts very smoothly in organic solvents with catechols, pyrogallols and 1,2-diketones to stable paramagnetic diphenylthalliumsemiquinone and diphenylthalliumsemidione complexes respectively. This reaction has been investigated with 43 different ligands in numerous solvents. Therefore its general application is proofed.The ESR-spectra of these solutions show the hydrogen hyperfine structure of the ligands and an unusual large coupling which we assign to magnetic interaction of the free electron with the ²⁰³Tl and ²⁰⁵Tl nuclei. The thallium splittings observed depend remarkably on the ligands used. We refer this to different solvation phenomena.Semiquinones of the pyrogallol type show on principle two different radical types. Small concentrations of diphenylthallium hydroxide produce $\text{1}\text{1}$ complexes. These can be converted into $\text{1}\text{2}$ complexes by addition of further amounts of diphenyl thallium hydroxide.The ESR-spectra of the semiquinone-and the semidione-thallium complexes exhibit an unusually strong solvent dependence of the thallium coupling and of the g-factor. It is possible to explain both variations uniformly by the different donor ability of the solvents used.All complexes investigated indicate remarkable temperature dependence of the thallium splitting and the g-factor. The thallium couplings show a positive temperature gradient whereas the g-factor decrease with increasing temperature as expected.Based on the sum of the observed effects, we assume that the radicals observed by us are ion pairs in which a diphenylthallium cation interacts with the semiquinone- or semidione-anion, respectively.     

Selective formation of peroxy-p-quinolato Co(III) complexes in the oxygenation of 4-alkyl-2,6-di-t-butylphenols with Co(II)-Schiff's base complexes

The oxygenation of 4-alkyl-2,6-di-$\text{t}$-butylphenols ($\text{2}$) with Co(II)-Schiff's base complexes in aprotic solvents such as CH₂Cl₂, THF, Py, and DMF leads to highly selective formation of the corresponding peroxy-$\text{p}$-quinolato Co(III) complexes. The reaction proceeds by mechanism involving a rate determining hydrogen abstraction by superoxo Co(III) species from $\text{2}$ giving phenoxy radical, rapid step of electron transfer from Co(II) complex to the phenoxy radical, and dioxygen incorporation into phenolato Co(III) complex thus formed.     

Unusual rearrangement of σ-vinylpalladium complexes into η2-olefin complexes. The structure of (η2-1-triphenylphosphonium-2-carbomethoxyethylene)(triphenylphosphine)iodopalladate

β-Substituted σ-vinylpalladium complexes [Pd(σ-CHCHCOOR)(PPh₃)₂(X)] (I) (X = Cl, I; R = Me, Et) have been obtained by interaction of the E- and Z-β-halogen acrylates with tetrakis(triphenylphosphine)palladium. On heating complexes I rearrange into isomeric η²-olefin-ylidepalladium complexes [$\text{P}$$\text{dCH(COOR)-C}$HPPh₃(PPh₃)(X)] (II). The structure of these com X-ray study of the compound with X = I, R = Me.     

The effect of the solvent upon the rates and machanisms of organometallic reactions: VII. A 19F NMR study of complexation of CF3 HgX (X = Cl,I, OCOCF3)

The concentration and temperature dependence of J(¹⁹⁹HgC¹⁹F) for solutions of CF₃HgX (X = Cl, I, OCOCF₃) in various solvents shows that in inert solvents these molecules exist mainly as non-solvent dimers (X = I or OCOCF₃) or as monomers (X = Cl). In strongly coordinated solvents $\text{1}\text{2}$ complexes are largely formed from CF₃HgX and the electron-donating solvent molecules. In pyridine solution an equilibrium exists between the $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes. Complexes of the type CF₃HgX·D are T-shaped and have a higher relative content of s-electrons in the HgCF group compared with tetrahedral CF₃HgX·2D complexes.     

Anionic tricarbonyl derivatives of molybdenum and tungsten and their reactions with allyl halides

A series of carbonylmetallate anions $\text{fac}$-[MX(CO)₃L₂]^?, where M = Mo or W, X = Cl, Br or I and L₂ = 1,10-phenanthroline(phen) or 2,2′-bipyridine(bipy) have been prepared from the corresponding $\text{cis}$-M(CO)₄L₂ complexes. No evidence of $\text{fac}$-to $\text{mer}$-isomerisation was evident on dissolution, although in MeCN solvolysis occurred with the formation of $\text{fac}$-M(CO)₃L₂(MeCN). Reaction of the anions with various allyl halides resulted in high yields of η³-allyl complexes [MX(CO)₂(η³-RC₃H₄)L₂]. The significance of these observations for the mechanism of the allyl oxidative-addition reaction are discussed.     

Organothallium compounds X the formation of polyfluorophenylthallium compounds by desulphination reactions

The acetatobis(polyfluorophenyl)thallium(III) compounds R₂TlO₂CCH₃ (R = C₆F₅, $\text{p}$-HC₆F₄, or $\text{m}$-HC₆F₄) have been prepared by sulphur dioxide elimination reactions from the appropriate lithium polyfluorobenzenesulphinates and thallic trifluoroacetate or acetate under mild conditions. Owing to reduction of the thallic salt by liberated sulphur dioxide, good yields required the stoichiometry 2LiO₂SR: 3TlX₃ (X = O₂CCF₃ or O₂CCH₃). The reactions are considered to proceed via thallium(III) $\text{S}$-sulphinate complexes and a possible mechanism is discussed.     

Synthesis of erythrinin A,a naturally occurring pyranoisoflavone

Erythrinin A ($\text{10}$) has been synthesised by the oxidative rearrangement of dihydropyranochalcone $\text{1}$ with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal $\text{2}$, followed by cyclisation to $\text{3}$, demethylation to $\text{6}$ and dehydrogenation. Compound $\text{10}$ could also be obtained from chalcone $\text{4}$ on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone $\text{7}$ was oxidatively rearranged with TTN in TMOF, to $\text{8}$ which on treatment with HCl yielded $\text{10}$.     

The reactions of a secondary phosphite with chloro- and pentan-2,4-dionato complexes of iridium(I) and rhodium(I)

The secondary phosphite $\text{OCH}{}_2\text{CMe}{}_2\text{CH}{}_2\text{OP}$(O)H reacts with chlorobis(cyclooctene) rhodium(I) dimer to give RhX(R₂POHOPR₂)₂(R₂POH) (X=H, Cl) and RhCl₂(R₂POHOPR₂)(R₂POH)₂ where R₂PO = $\text{OCH}{}_2\text{CMe}{}_2\text{CH}{}_2\text{P}$O. The iridium analogue yields corresponding products. The phosphite reacts with bis-(cyclooctene) pentan-2,4-dionatorhodium(I)to give Rh(R₂POHOPR₂)₃ and with the corresponding iridium complex to produce Ir(acac)(R₂POHOPR₂)₂. Some of the complexes act as catalysts or catalytic precursors for the stereoselective reduction of 4-t-butylcyclohexanone.     

Electrochemical reductions of substituted pyridinium 2-pyridylcarbonylmethylides,their Pt(II) complexes,and substituted n-(2-pyridylcarbonyl)methylpyridinium perchlorates

The title pyridinium salts and pyridinium ylide-platinum(II) complexes have been reduced through a one-electron process at more positive potentials by 0.3 $\text{\$}\text{?}$0.6 V than the corresponding ylides. Both the reduced pyridinium salts and Pt(II)-ylide complexes reacted with dioxygen, followed by elimination of the N-methylene and ylide protons to form pyridinium ylides and Pt(II)-pyridinium ylide complexes containing the three-coordinate ylide carbon atom, respectively.     

Optical resolution of tricarbonyl(1-carboxycyclohexa-1,3-diene) iron and the absolute configuration of the products

Resolution of the acid ($\text{1}$) (shown as the (+)-isomer) into its optically pure (+) and (?) isomers and reduction of the CO₂H yields the 2-Me derivative ($\text{2}$) (shown as the (?)-isomer). The absolute configuration of ($\text{2}$) is defined by conversion of the salt ($\text{3}$) of known configuration into ($\text{2}$) and ($\text{4}$). This is the first resolution leading to preparation of pure complexes of known absolute configuration.     

Thermal investigation of diamine complexes of Zn(II) in the solid state

The complexes [Zn(en)₃]X2·n H₂O, where en = ethylenediamine, X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄, n = 1 or 0.5, and [Zn(tn)₂]X₂·n H₂O, where tn=1,3-diaminopropane, X=Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄, n = 0 or 0.25, have been synthesized and their thermal investigations carried out. The complexes were characterized by elemental analysis and IR spectral data. These complexes have been observed to decompose through several isolable as well as non-isolable complex species as intermediates during heating. [Zn(tn)₂]SO₄ undergoes solid-state phase transition in the temperature range 126–145°C. ZnenSO₄ and ZntnX₂ (X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄) have been synthesized pyrolytically in the solid state from their corresponding mother diamine complexes. ZnenSO₄ and ZntnX₂ (X = Cl^?, Br^? or $\text{1}\text{2}$SO^2?₄) complexes decompose through non-isolable hemidiamine species. ZnX₂ (X = Cl^? or Br^?) complexes of tn undergo melting after formation of the monodiamine species. In contrast, the corresponding en complexes undergo melting at non-stoichiometric composition. Diamine (en or tn) is found to be bridging in all monodiamine (en or tn) complexes; whilst their mother complexes possess chelated en or tn. The thermal stability sequence of en and tn complexes of Zn(II) is ZnCl₂ < ZnBr₂ < ZnSO₄. ΔH values are reported for some steps of decomposition. Possible mechanistic paths have been reported for each step of decomposition.     

The crystal structure of hexathallium(I) hexatellurodigermanate(III), Tl6[Ge2Te6]

The new compound Tl₆[Ge₂Te₆] was prepared by thermal synthesis from the elements. The material is triclinic, space group $\text{P}\text{1}$, with a = 9.471(2), b = 9.714(2), c = 10.389(2) Å, α = 89.39(1), β = 97.27(1), γ = 100.79(1)°, and Z = 2. The crystal structure was determined from single-crystal intensity data measured by means of an automated four-circle diffractometer and refined to an R value of 0.053 for 1831 observed reflections. Tl₆[Ge₂Te₆] is characterized by Ge₂Te₆ units with GeGe bonds which are linked into a three-dimensional structure by Tl atoms coordinated to essentially six Te atoms. The most important mean distances are $\text{d}\text{GeGe}\text{) = 2.456}$ Å, $\text{d}\text{(}\text{GeTe}\text{) = 2.573}$ Å, and $\text{d}\text{(}\text{TlTe}\text{) = 3.515}$Å. The lone 6s electron pairs of the thallium(I) atoms exhibit significant stereochemical activity. Tl₆[Ge₂Te₆] represents a new structure type.     

Regioselective synthesis of 4-alkylpyridines via 1,4-dihydropyridine derivatives from pyridine

N-Ethoxycarbonylpyridinium chloride ($\text{1}$) reacted with RCu·BF₃ at 4-position with almost complete regioselectivity (better than 99%) to afford the corresponding 1,4-dihydropyridine derivatives ($\text{2}$) in high yields (81≈94%). The dihydropyridines were readily oxidized by oxygen to give 4-alkylpyridines ($\text{4}$: 38≈68% yields).     

Some observations relating to phosphorylation methods in oligonucleotide synthesis

A very convenient procedure for the conversion of ($\text{N}$),O-5′-protected deoxyribonucleosides ($\text{8}$) into the triethylammonium salts of the corresponding 3′-($\text{o}$-chlorophenyl) phosphates ($\text{9}$) is described. Good yields of partially-protected 3′→5′-dinucleoside phosphates ($\text{10}$) are obtained from the latter ($\text{9}$) and 3′-unprotected nucleoside building blocks ($\text{12a}$).     

Syntheses of σ-cyclobut-1-en-3-onyl complexes by cycloaddition of ketenes to some transition metal alkynyl complexes

Reactions of ketenes (R¹R²CCO) with (η⁵-C₅H₅)Ni(PPh₃)CCR (I) and (η⁵-C₅H₅)Fe(CO)(L)CCR (III, L = CO and PPh₃) give σ-cyclobut-1-en-3-onyl complexes, {(η⁵-C₅H₅)Ni(PPh₃)$\text{CC(R)COC}$}R¹R² (VI) and (η⁵-C₅H₅)Fe(CO)(L)$\text{CC(R)COC}$R¹R² (IX)}, (2 + 2) cycloaddition products, in good yields. The σ-cyclobutenonyl complexes also can be prepared by the reaction of I and III with acyl chlorides in the presence of triethylamine.