Spirocyclization of 1-(o-aminophenyl)cycloalkanols and 1-(2′-amino-3′-pyridinyl)cycloalkanols

A one-step synthesis of spiro[cycloalkane-1,4′-2H-3′,1-benzoxazin]-2′-ones and spiro[cycloalkane-1,4′-1H-pyrido[2′,3′-d][1,3′]oxazin]-2′-ones, obtained in good yield from the corresponding 1-(o-aminophenyl) and 1-(2′-amino-3′-pyridinyl)cycloalkanols is described using ethyl carbonate in presence of n-butyllithium.     

Synthesis and characterization of maleimide polymers with pendant pyrazole groups. IV. Copolymerization of pyrazole-modified maleimides with vinyl ethers

The synthesis of maleimides that have pyrazolic or bipyrazolic pendant groups is described. Their homopolymerization and their copolymerization with 2-chloroethyl vinyl ether (CEVE) is reported. The homopolymerizations of such maleimides were performed under various conditions and led to low molecular-weight polymers. However, alternating copolymers were obtained from CEVE as comonomers whatever the monomers feed compositions. A similar behavior was also observed for maleimides that do not exhibit any spacer, whereas for bulky vinyl ethers, random copolymers were produced. A comparison of the thermal behavior between these copolymers (glass transition temperatures, T_g, and decomposition temperatures) and other copolymers having different spacers between the nitrogenated cycles and the chain are related. Thus, an important decrease of T_g, was observed when C₃H₆CO₂CH₂ groups were used as the spacer instead of methylene groups. Moreover, the thermal weakness of these copolymers may come from the substituents of the vinyl ether and is discussed. © 1994 John Wiley & Sons, Inc.     

Microphase separation of cationic poly(N-isopropylacrylamide) copolymers in water: Effect of the migration of charges

The structures of aqueous copolymer solutions have been examined through small angle neutron scattering. The copolymers contained mostly N-isopropylacrylamide (NIPAM) monomers. Poly (NIPAM) solutions have a lower critical solution temperature (LCST), above which the macromolecules separate from water. A small fraction of ionizable N,N-[(dimethylamino) propyl] methacrylamide (MADAP) monomers was introduced into the macromolecules. This had dramatic consequences on the solution behavior at temperatures above the LCST of PNIPAM, where phase separation would have been expected for the homopolymer. When all MADAP monomers were ionized, it was found that the solutions resisted the phase separation. At short spatial scales, the chains were collapsed but at large scales they formed branched aggregates that did not separate out of water. When only half of the MADAP monomers are ionized, the electrical charges were able to redistribute themselves along the chains. In this case, the rise in temperature caused a microphase separation where the electrical charges were relocated on a fraction of the chains that remained in solution.The other chains (or section of chains) formed large nodules of a polymer rich phase.     

One-pot synthesis of β-amino acid derivatives via addition of bis(O-silyl) ketene acetals on iminium salts

We report here our findings on a new and highly efficient strategy for the synthesis of β-amino acids involving the addition of bis(O-silyl) ketene acetals on Mannich type iminium electrophiles.     

Synthèse de flavones et de xanthones dans la série du benzo[4,5]thiophène

We describe the first synthesis of 2-arylbenzo[4,5]thieno-[2,3-b]pyran-4-one and of 2-arylbenzo [4,5] thieno [3,2-b] pyran-4-one, from benzo [4,5] thiophene and we have extended these cyclizations to obtain the heterocyclic analogs of the xanthones.     

Linear spin-zero quantum fields in external gravitational and scalar fields

The quantum theory of both linear, and interacting fields on curved space-times is discussed. It is argued that generic curved space-time situations force the adoption of the algebraic approach to quantum field theory: and a suitable formalism is presented for handling an arbitrary quasi-free state in an arbitrary globally hyperbolic space-time.For the interacting case, these quasi-free states are taken as suitable starting points, in terms of which expectation values of field operator products may be calculated to arbitrary order in perturbation theory. The formal treatment of interacting fields in perturbation theory is reduced to a treatment of free quantum fields interacting with external sources.Central to the approach is the so-called two-current operator, which characterises the effect of external sources in terms of purely algebraic (i.e. representation free) properties of the source-free theory.The paper ends with a set of Feynman rules which seems particularly appropriate to curved space-times in that it takes care of those aspects of the problem which are specific to curved space-times (and independent of interaction). Heuristically, the scheme calculates in-in rather than in-out matrix elements. Renormalization problems are discussed but not treated.Work partly supported by the Schweizerische Nationalfonds     

Teaching Operational Research Technique

Good technique, i.e. competence in carrying out operational research, is as vital for the practitioner to acquire as competence in the traditional ‘techniques’. It is suggested that universities should teach students how to conduct simple projects prior to alerting them to more sophisticated methodological issues.As an aid to this task, the traditional five or six parts of an operational research project are broken down and extended into 39 steps, and regrouped into three phases. Also, five skills are identified as being conceptually essential to "good" operational research, which students can develop through tackling suitable case studies.     

Hyperfine structure in the configurations4f 4 6s 2 and4f 4 5d 6s of Nd I

The high resolution laser-atomic-beam technique was used to investigate the hyperfine structure in Nd I 4f ⁴6s ^{2 5} I,⁵ F,⁵ S and 4f ⁴5d6s ⁷ L,⁷ K,⁷ I,⁷ H. The metastable states were populated by an arc discharge burning in the atomic beam. The measured hyperfine constantsA andB of the levels of 4f ⁴6s ² and 4f ⁴5d6s allow a parametric analysis to be performed using the effective tensor operator formalism. The experimental radial integrals of the 4f and 5d electrons fit with those of the other lanthanides. The 4f radial integrals are in agreement with values of optimized Hartree-Fock-Slater calculations. The spectroscopic quadrupole moments of¹⁴³Nd and¹⁴⁵Nd are deduced from the 4f parameters:Q _I =?0.610(21) b and ?0.314(12) b, respectively. TheQ _I resulting from the 5d parameter are in satisfactory agreement with these values. The hyperfine anomaly due to thes electron in 4f ⁴5d 6s amounts to about 1%.     

Synthesis of some 5-Aryl-4,5-dihydro[1]benzoxepin-3(2H)-ones and 5-aryl-5,6,8,9-tetrahydro-7H-benzocyclohepten-7-ones from benzoxepinoisoxazolone and benzocycloheptaisoxazolone derivatives

Some 5-aryl-4,5-dihydro[1]benzoxepin-3(2H)-ones and 5-aryl-5,6,8,9-tetrahydro-7H-benzocyclohepten-7-ones were synthesized by hydrogenolytic cleavage of the isoxazole ring of 4-aryl-3-oxo-3,3a,4,10-tetrahydro[1]-benzoxepino[3,4-c]isoxazoles or 4-aryl-3-oxo-3a,4,9,10-tetrahydro-3H-benzo[4,5]cyclohepta[1,2-c]isoxazoles which in turn were prepared from ethyl 3-oxo-4-phenoxybutanoate or ethyl 3-oxo-5-phenylpentanoate by simple methods.     

First anhydrous gold perchlorato complex: ClO(2)Au(ClO(4))(4). Synthesis and molecular and crystal structure analysis

Chlorine trioxide, Cl(2)O(6), reacts with Au metal, AuCl(3), or HAuCl(4).nH(2)O to yield the well-defined chloryl salt, ClO(2)Au(ClO(4))(4). The crystal and molecular structure of ClO(2)Au(ClO(4))(4) was solved by a Rietveld analysis of powder X-ray diffraction data. The salt crystallizes in a monoclinic cell, space group C2/c, with cell parameters a = 15.074(5), b = 5.2944(2), and c = 22.2020(2) A and beta = 128.325(2) degrees. The structure displays discrete ClO(2)(+) ions lying in channels formed by Au(ClO(4))(4)(-) stacks. Au is located in a distorted square planar environment: Au-O = 1.87 and 2.06 A. [ClO(4)] groups are monodentate with ClO(b) = 1.53 and ClO(t) = 1.39 A (mean distances; O(b), oxygen bonded to Au; O(t), free terminal oxygen). A full vibrational study of the Au(ClO(4))(4)(-) anion is supported by DFT calculations.