The Synthesis of Trimethylcyclopentane-carboxylic Acids

(1RS, 5SR)-2,2,5-Trimethylcyclopentane-1-carboxylic acid ( 17 ) and (1r, 2RS, 5SR)-1,2,5-trimethylcyclopentane-1-carboxylic acid ( 19 ) are the starting materials for the α-alkynone routes to (±)-capnellene and for similar efforts towards ptychanolide. Since 17 and 19 have, so far, been available only by a branching reaction from the same precursor, the cyanohydrin mixture 2 / 3 , a modified synthesis for 17 and a new one for 19 was developed (Scheme 1). The common precursor 2 / 3 was treated with POCl₃ which effected normal dehydration to 6 (47%, major path) in competition with Me migration to 8 and 9 (17%). The minor path to 8 and 9 could be reduced to 3% when SOCl₂ was used for the dehydration of 2 / 3 . This reaction was the basis for an improved synthesis of 17 from 1 , using the steps b, e, i, r, and v see Scheme 1 in an overall yield of 35%. The POCl₃ reaction was also studied with the pure cyanohydrins 2 and 3 , the configurations of which were determined by an X-ray analysis of 2 . Me migration did not occur form 2 but only from 3 (25%), which has HO? C(1) and H? C(5) in a cis position. With SOCl₂, 3 underwent only 5% Me migration. The new synthesis of 19 started with 4 using the steps h, n, p, and s (see Scheme 1) in an overall yield of 68%.     

Probing proton dissociation in ionic polymers by means of in situ ATR-FTIR spectroscopy

The hydration process of cationic membrane protogenic groups was investigated using in situ ATR-FTIR spectroscopy. The aim of this study is to provide a relationship between the hydration degree of the membrane and the dissociation state of exchange sites inside the polymer material. IR spectra were recorded by means of an environmental device specifically manufactured to allow the control of water vapour pressure in equilibrium with the sample. The behaviour of Nafion 112 and sulfonated poly(ether ether ketone) (S-PEEK), in both proton and sodium forms, was compared. IR data, analyzed and fitted in the 800-1850 cm(-1) spectral range, gave precise information on the assignment of sulfonic group vibrational modes. The results of this study improve the understanding of the transition phenomena between dissociated and undissociated states of the grafted sites in protonic conductors.     

Monitoring of the microstructure of ion‐irradiated nuclear ceramics by in situ Raman spectroscopy

Raman spectroscopy is an efficient technique for studying the evolution of microstructure of materials under irradiation. For that purpose, a Raman spectrometer has been recently installed at the JANNUS‐Saclay platform. In this paper, we describe the new setup for in situ experiments. These in situ experiments allowed following the microstructural evolution of different materials (SiC, ZrO₂ and B₄C) as a function of ion fluence on a single sample (either single crystal or polycrystalline ceramics) under the same irradiation conditions. Our results show that Raman spectroscopy is a versatile non‐contact technique for studying on‐line crystalline phase changes or amorphization of irradiated iono‐covalent solids. A detailed analysis of Raman spectra is provided for the three materials (SiC, ZrO₂ and B₄C) investigated in this study, revealing quite different behaviors upon irradiation. Basically, Raman spectroscopy gives insight on these evolutions at the level of bonds given by specific phonon modes, in good agreement with Rutherford backscattering channeling (RBS/C), X‐ray diffraction (XRD) or transmission electron microscopy (TEM) data, which provide information at a long‐range scale. Copyright © 2015 John Wiley & Sons, Ltd.     

Optically Active Tetra‐tert‐butyl‐P5‐deltacyclene Epimers: Preparation,Spectroscopy, Dynamic Equilibriums,H/D Exchange,and Transition‐Metal Complex Chemistry

On the basis of isolated diastereomeric triorganylstannyl‐P₅‐deltacyclenes 7′ and 7′′ , almost pure enantiomers of their destannylation products 8′ and 8′′ are now available. These stereochemically inert cage chiral species contain a configurationally labile P1?H1 group that defines two epimers 8 a and 8 b of each of the enantiomers, which are connected by a rapid equilibrium. Mirror‐symmetric circular dichroism (CD) spectra of the enantiomeric cages are compatible with the identification of epimers. A simulation of the CD spectrum of the major epimer 8′a relates the cage chirality of the system to the observed chiroptical effects. Both cage epimers and two of the phosphorus cage atoms are active as ligands with respect to [M(CO)₅] fragments of Cr, Mo, and W. Four almost isoenergetic regio‐ and stereoisomers of the resulting mononuclear complexes are formed for these metals, but only one of the isomers per metal crystallized in the case of the racemic series of the complexes. The enantiopure versions of cages and cage complexes, however, did not crystallize at all, a well‐known phenomenon for chiral compounds. CD spectra of the optically active complex isomer mixtures are close to identical with the CD spectra of the related free cages and point again to the chiral cages as the dominant source of the CD effects of the complexes. [(Benzene)RuCl₂] complexes of the cage ligand 8 behave totally differently. Only a single species 12 =[(benzene)RuCl₂ ?8 b ] is formed in almost quantitative yield and the minor epimer 8 b plays the role of the ligand exclusively. The reaction works as well for the separated enantiomeric cage versions to yield the highly enriched enantiomers 12′ and 12′′ separately. An efficient kinetic resolution process was identified as the main reason for this finding. It is based on a high stereo‐ and regiochemical flexibility of the P?C cage ligand that is capable of adjusting to the specific requirements of a suitable transition‐metal complex fragment. Such ligand flexibility is regularly observed in metalloenzymes, but is a very rare case in classical and organometallic complex chemistry.     

Tetravalent metal complexation by Keggin and lacunary phosphomolybdate anions

We report the synthesis, spectroscopic and structural characterization, and computational analysis of a series of phosphomolybdate complexes with tetravalent metal cations. The reaction between Ce (IV) and Th (IV) with phosphomolybdate at the optimum pH for the stabilization of the lacunary heteropolyoxometalate anion, [PMo 11O 39] (7-), results in the formation of compounds containing the anions [Ce(PMo 11O 39) 2] (10-) and [Th(PMo 11O 39) 2] (10-), respectively. Single crystal X-ray diffraction analysis was performed on salts of both species, Cs 10[Ce(PMo 11O 39) 2].20H 2O and (NH 4) 10[Th(PMo 11O 39) 2].22H 2O. In both anionic complexes the f-block metal cation is coordinated to the four unsaturated terminal lacunary site oxygens of each [PMo 11O 39] (7-) anion, yielding 8 coordinate sandwich complexes, analogous to previously prepared related complexes. Spectroscopic characterization points to the stability of these complexes in solution over a reasonably wide pH range. Density functional analysis suggests that the Ce-O bond strength in [Ce(PMo 11O 39) 2] (10-) is greater than the Th-O bond strength in [Th(PMo 11O 39) 2] (10-), with the dominant bonding interaction being ionic in both cases. In contrast, under similar reaction conditions, the dominant solid state Zr (IV) and Hf (IV) complexes formed contain the anions [Zr(PMo 12O 40)(PMo 11O 39)] (6-) and [Hf(PMo 12O 40)(PMo 11O 39)] (6-), respectively. In these complexes the central Group 4 d-block metal cations are coordinated to the four unsaturated terminal lacunary site oxygens of the [PMo 11O 39] (7-) ligand and to four bridging oxygens of a plenary Keggin anion, [PMo 12O 40] (3-). In addition, (NH 4) 5{Hf[PMo 12O 40][(NH 4)PMo 11O 39]}.23.5H 2O can be crystallized as a minor product. The structure of the anion, {Hf[PMo 12O 40][(NH 4)PMo 11O 39]} (5-), reveals coordination of the central Hf (IV) cation via four bridging oxygens on both the coordinated [PMo 11O 39] (7-) and [PMo 12O 40] (3-) anions. Unusually, the highly charged lacunary site remains uncoordinated to the Hf metal center but instead interacts with an ammonium cation. (31)P NMR indicates that complexation of the Keggin anion, [PMo 12O 40] (3-), to Hf (IV) and Zr (IV) will stabilize the Keggin anion to a much higher pH than usually observed.     

Consecutive Application of the α-Alkynone Cyclization: Total Synthesis of (±)-Δ9(12)-Capnellene

The synthesis of the (±)-form of the marine sesquiterpene (–)-Δ⁹⁽¹²⁾-capnellene ( 1 ) by double application of the a-alkynone cyclization is described. Starting with 2, 2, 5-trim ethylcyclopentanone ( 2 ), the elaboration of the tricyclo [6.3.0.0^2,6]undecane C-skeleton of 1 proceeded through the a-alkynone 3 , which was cyclized thermally to the bicyclo [3.3.0]octenone 4. For the anellation of the third five-membered ring, 4 was transformed into the a-alkynone 5 and the latter cyclized thermally to a mixture of the angular triquinenone 6 and the linear triquinenone 7. The last steps in the synthesis of (±)-Δ⁹⁽¹²⁾-capnellene ( 1 ) were then accomplished from 7 by known methods.     

Chemical behavior of optically active poly[thio 1-(N,N-disubstituted aminomethyl) ethylenes] in CuCl2-methanol mixtures: Induced optical activity of bound Cu(II)

(+)-Poly[thio 1-(N-sec-butyl-N-methylaminomethyl) ethylene] (I) and (-)-poly[thio 1-(N-methyl-N-(1-phenylethyl)aminomethyl) ethylene] (II) are soluble in methanol or in a 10/90 dioxane-methanol mixture in the presence of CuCl₂. This salting-in effect results from interactions between macromolecules and this salt. With a large excess of salt (molar ratio > 8) a precipitate is obtained whose composition is close to a CuCl₂:monomer unit ratio of unity. Ultraviolet, optical rotatory dispersion (ORD) and circular dichroism (CD) spectra in solution are described. The three extrinsic Cotton effects observed between 300 and 800 nm are assigned to charge transfer and d-d electronic transitions of Cu(II) complexed with the macromolecules. In the same solvent system, Cu(II) shows similar induced optical activity in the presence of a nonaminated homolog, (+)-poly(propylene sulfide) taken as a model of the chains of I and II. No extrinsic Cotton effects are observed in the presence of an optically active tertiary amine without the thioether sulfur atom, (+)-N-sec-butyl-N-methyl-N-(oxirane-2-ylmethyl)amine. It is concluded that Cu(II) gives rise to charge-transfer complexes with sulfur atoms, while tertiary amine groups are probably protonated in this particular medium.     

Levels of210Po in marine species of the south Atlantic Ocean

Data are presented for²¹⁰Po levels in edible parts of marine species significant in the diet of the Argentine population. The sample collection sites were situated between 35° and 45° S in the Atlantic Ocean. The specific activities obtained, expressed per wet veight and with a 95% confidence level, ranged between 31.3±9.1 mBq kg^–1 for pollack (Genypterus blacodes) and 1790±280 mBq kg^–1 for squid (Illex argentinus). Hake (Merluccius hubbsi) followed by squid are the major contributors to the dose. The annual committed effective doses were 0.7 mSv and 0.6 mSv and the effective collective doses were 24 man·Sv and 20 man·Sv, respectively, for these species. For the remainder, because of both their low consumption rates and low specific activities, the corresponding doses were negligible compared with the former.