Phosphinofenchol or metastable phosphorane? Phosphorus derivatives of fenchol

Not the expected phosphinofenchol 1 but phosphorane 2 is obtained after reaction of 2-lithio(diphenylphosphino)benzene with (-)-fenchone. Surprisingly, ONIOM(B3LYP/6-31G*:UFF) computations of 1 and 2 as well as B3LYP analyses of smaller model systems point to a lower thermodynamic stability of phosphoranes relative to their isomeric alkoxyphosphines. An analogue inherent instability is computed for the methylphosphorane 10, which is also synthesized and characterized by X-ray analysis. Decreasing ring size in cyclic phosphoranes, that is, from five- to four-membered ring systems, destabilizes cyclic phosphoranes even more. This computational prediction is verified experimentally by reaction of lithiomethyl(diphenylphosphine) with (-)-fenchone and subsequent isolation of the corresponding phosphinofenchol. Protonation or alkylation of phosphoranide intermediates can account for the formation of metastable phosphoranes.     

Kristallstruktur von Dichloro- und Dihydroxo-tetraorganyldistannoxanen

Crystal Structure of Dichloro- and Dihydroxo-tetraorganyldistannoxanes X-ray structure determination of 1,3-dichloro-1,1,3,3-tetraisopropyl-distannoxane and of 1,3-dihydroxo-1,3-di-tert.-butyl-1,3-bis(trimethylsilylmethylene)-distannoxaneshows the presence of dimeric molecules. The basic structure consists of three condensed four-membered rings, all lying in one plane. The inner ring is made up of two tin and two oxygen atoms; the outer ones consist of two tin atoms, one oxygen atom and a chlorine or hydroxide bridge, respectively. All tin atoms are in trigonal bipyramidal coordination.     

Mass spectrometry of π-complexes of transition metals : V. Dimeric (π-cyclopentadienyl)dicarboxylatovanadium complexes

Mass spectra of dimeric (π-cyclopentadienyl)dicarboxylatovanadium complexes [π-C₅H₅V(OOCR)₂]₂, have been studied. The principal paths of fragmentation of the trihaloalkyl derivatives involve the formation of VHal bonds, whereas VO bonds are formed during decomposition of acetato and formato complexes. An unusual increase in stability of dimeric and monomeric ions of the alkyl derivatives is observed in going from R = CH₃ to R = CF₃. With aromatic complexes, only ions containing a single metal atom occur.     

Fluxional behaviour of π-bonded acetylenes

Some cationic five coordinate complexes of formula [Os(CO)(NO)L₂A]PF₆ (L = tertiary phosphine, A = an acetylene) have been prepared by reaction of the appropriate acetylene with [Os(CO)(NO)L₂(acetone)]PF₆; the variable temperature ¹H NMR spectra of some of these indicate that the coordinated π-acetylene undergoes fluxional behaviour.     

The synthesis of 2,2'-Dinor-carotenoids (author's transl)]

The Synthesis of 2,2′-Dinor-carotenoids. 2,2′-Dinor-carotenoids which include the naturally occurring actinioerythrol ( 1 ) and the blue carotenoid violerythrin ( 2 ) have been obtained by total synthesis. The synthesis starts with acetone and acetylene and yields compounds 1 and 2 as well as other carotenoids of the same type.     

Syntheses based on 5-methylfurfural

Conclusions A series of derivatives of furan and tetrahydrofuran were synthesized on the basis of 5-methylfurfural: alkyl(5-methylfuryl)carbinols, alkyl(5-methyltetrahydrofuryl)carbinols, 2-methyl-5-alkenylfurans, 2-methyl-5-alkylfurans, and 2-methyl-5-alkyltetrahydrofurans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 1829–1831, October 1966.     

Fast and simple radiochemical method for the separation of uranium,thorium and lanthanum

The concept of using paper chromatography on papers impregnated with liquid anion or cation exchangers is extended to the separation of trace elements through filtration on filter papers loaded with suitable extractant. The uptake of uranium, thorium and lanthanum from HCl and HNO₃ media of different molarities by a filter paper treated with tri-octyl amine (TOA) is investigated. The effect of the different parameters on the uptake of the studied elements is experimented. A simple and fast radiochemical procedure is developed for the separation of La, Th and U from each other.     

Behavior and characteristics of biogenic amines, ornithine and lysine derivatized with the o-phthalaldehyde-ethanethiol-fluorenylmethyl chloroformate reagent

The stability and characteristics of the ornithine (Orn), lysine (Lys), putrescine (Put), cadaverine (Cad), 1,7-diaminoheptane (Diah), spermidine (Spd) and spermine (Spm) derivatives obtained with the o-phthalaldehyde (OPA)-ethanethiol (ET)-fluorenylmethyl chloroformate (FMOC) reagent has been investigated. The stoichiometry of the introduced, two-step derivatization process has been followed by photodiode array (DAD) and fluorescence (FL) detections, simultaneously, while the composition of derivatives was confirmed by on-line HPLC-electrospray ionization (ESI) MS measurements. Depending on the composition of the OPA reagents, in addition to the secondary amino group-containing Spd and Spm, under common aqueous conditions also Orn and Lys do react with FMOC resulting in derivatives of various compositions. Applying the OPA-ET reagent of increasing methanol (Met) content (38-80%, v/v) the formation of the FMOC group containing Orn and Lys derivatives could be considerably decreased. Optimum elution condition (18 min, including equilibration) was developed for the simultaneous quantitation of Orn, Lys, Put, Cad, Diah, Spd and Spm, in the presence of the rest of protein amino acids. The practical utility of the method was demonstrated by the analysis of mouse tissues. Average reproducibility of quantitations, characterized with the relative standard deviation percentages of fluorescence intensities and UV responses, in order of listing, proved to be 2.1% and 2.1%, respectively.     

ESR study of free radicals chemically generated at high pressure

Free radicals generated by the thermal decomposition of benzoyl peroxide in polyacrylnitrile were studied by the ESR method at 700 MPa between 100 and 130°C. The formation and decay of macroradicals were investigated and the mechanism of macroradical generation is discussed.

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700 MPa 100 130°C. .

     

Reactions of molybdenum and tungsten halides with acetylenic hydrocarbons: an approach to the structure and pathways of formation of metathesis catalysts

A number of acetylene and mixed acetylene-nitrile complexes of tungsten and molybdenum halides have been prepared and investigated. Depending on the acetylene and the reaction conditions, one or more acetylene molecules may be coordinated to the metal. In the latter case acetylenes are coordinated not as single molecules but in systems of conjugated non-aromatic double bonds. On the basis of the supposed structure of such species and on their pyrolysis products a decomposition scheme is proposed, which consider the formation of apparent metathesis products as a side reaction of the cyclotrimerization of acetylenes to aromatic hydrocarbons.