Millimeter wave spectrum of bromomethyl radical, CH2Br

The rotational spectra of the two isotopic species of the bromomethyl radical, CH2 79Br and CH2 81Br, have been observed in their ground electronic state 2B1 in the 180-470 GHz frequency region, corresponding to a-type transitions from N=8-7 to N=21-20. The radical was produced by hydrogen abstraction of methylbromide (CH3Br) either by chlorine or by fluorine atoms in a free space cell. Hyperfine structure due to the bromine nucleus has been resolved in the observed spectra, and the rotational constants as well as the fine and hyperfine interaction constants were accurately determined for both isotopomers. The inertial defect was determined to be 0.028 96(20) and 0.028 95(20) amu A(2), for CH2 79Br and CH2 81Br, respectively, suggesting a planar structure. By fixing the [angle]HCH bond angle at 124.5 degrees , an effective molecular structure can be derived as r0(CBr)=1.848 A and r0(CH)=1.084 A. A comparison of the molecular structure of various halogen-substituted methyl radicals with respect to the planarity of these radicals is discussed.     

Templated scaffolds of cis- and trans-tetrahydrofuran γ-amino acids: γ-azido-β-hydroxy-tetrahydrofuran-2-carboxylates from pentono-δ-lactones

Short syntheses of enantiomeric templated scaffolds of cis- and trans-tetrahydrofuran γ-amino acids from pentono-δ-lactones derived from arabinose and ribose are reported; an unexpectedly efficient synthesis of a templated tetrahydrofuran β-amino acid by azide displacement of a triflate β to an ester function proceeds with remarkably little elimination. These materials should allow evaluation of such peptidomimetics to induce predisposition towards secondary structures.     

Photocatalytic degradation of adenosine triphosphate in an aqueous suspension of TiO<Subscript>2</Subscript>: a HPLC and <Superscript>1</Superscript>H-NMR study

Photocatalytic degradation process of ATP was followed by HPLC and ¹H-NMR measurements. Adenine was one of the major products when the aqueous ATP sample with TiO₂ dispersion was irradiated by UV light (λ = 365 nm) for 90 min. The ¹H-NMR spectra indicated the presence of another product (Z), which likely came from the ribose moiety in ATP. Photocatalytic generation of OH^˙ radicals on TiO₂ surface was concluded to be responsible for degrading ATP. A working hypothesis of the reaction process was proposed to account for the reaction products.     

Lipase-catalyzed domino kinetic resolution/intramolecular Diels-Alder reaction: one-pot synthesis of optically active 7-oxabicyclo[2.2.1]heptenes from furfuryl alcohols and beta-substituted acrylic acids

The first lipase-catalyzed domino reaction is described in which the acyl moiety formed during the enzymatic kinetic resolution of furfuryl alcohols (+/-)-3 with a 1-ethoxyvinyl ester 2 was utilized as a part of the constituent structure for the subsequent Diels-Alder reaction. The preparation of ester 2 from carboxylic acid 1 and the subsequent domino reaction were carried out in a one-pot reaction. Therefore, this procedure provides a convenient preparation of the optically active 7-oxabicyclo[2.2.1]heptene derivatives 5, which has five chiral, non-racemic carbon centers, from achiral 1 and racemic 3. The overall efficiency of this process was dependent on the substituent at the C-3 position of 3, and the use of the 3-methylfurfuryl derivatives, (+/-)-3 b and (+/-)-3 f, exclusively produced diastereoselectivity with excellent enantioselectivity to give (2R)-syn-5 (91->/=99 % ee) and (S)-3 (96->/=99 % ee). Similar procedures starting from the 3-bromofurfuryl alcohols (+/-)-3 h-j provided the cycloadducts (2R)-syn-5 j-q (93->/=99 % ee), in which the bromo group was utilized for the installation of bulky substituents to the 7-oxabicycloheptene core.     

Practical preparation of N-(1-alkynyl)sulfonamides and their synthetic utility in titanium alkoxide-mediated coupling reactions

Aliphatic and aromatic sulfonamides were alkynylated with 1-bromo-1-alkynes in the catalytic presence of CuI to give N-(1-alkynyl)sulfonamides in good to excellent yields. Racemization of optically active sulfonamides was not observed during this alkynylation. The acetylene-titanium complexes generated from the resultant N-(1-alkynyl)sulfonamides and Ti(O-i-Pr)₄/2 i-PrMgCl underwent regio-, olefinic stereo-, and diastereoselective addition to aldehydes to give virtually single allyl alcohols. Alternatively, inter- or intramolecular coupling reaction between N-(1-alkynyl)sulfonamides and another acetylene or olefin with the above titanium alkoxide reagent generated the corresponding titanacycles, hydrolysis of which furnished stereo-defined (sulfonylamino)dienes or cyclic compounds.     

Intramolecular michael addition reaction to chiral vinylic sulfoxides. An enantioselective synthesis of (R)- and (S)-1,7-dioxaspiro[5.5]undecane

(R)- and (S)-1,7-Dioxaspiro[5.5]undecane ((R)-1 and (S)-1), sex pheromone of an olive fly, was each stereoselectively synthesized using an intramolecular Michael addition of hydroxyl group to a chiral vinylic sulfoxide moiety as an asymmetric induction step.     

Study of electronic X-rays emitted from pionic and muonic atoms

The electronic X-ray energies of muonic atoms were precisely measured. The atomic number (Z) dependence of the energy difference between electronic X-rays of muonic atoms and Z-1 atoms (energy shift) was systematically investigated. The energy shifts in the low-Z region were compared with those of the high-Z region that had been obtained experimentally and theoretically in previous work. An obvious difference between these two regions was found in the atomic-number dependence of the energy shift. We also compared the energy shifts of muonic atoms with those of pionic atoms.     

A new and facile route to spiro-ketal skeleton via highly stereoselective CO bond formation by intramolecular Michael addition to δ,β-unsaturated sulfoxides

Diastereoisomerically pure (E)-and (Z)-2-methyl-1,6-dioxaspiro [4.5]-decane (insect pheromone) was efficiently prepared via a highly stereo controlled intramolecular Michael addition of hydroxyl group to an unsaturated sulfoxide moiety during the crucial cyclization step.     

A study of the electronic spectra of 9-fluorenone

The absorption and MCD spectra of 9-fluorenone are measured. The CD spectra of the β-cyclodextrin complex with 9-fluorenone are also measured. The assignment for the first (≈26.0 × 10³ cm^?1) and fourth (≈48.0 × ³ cm^?1) absorption band has been determined from the sign of the CD spectra by reference to the observed MCD spectra.     

Solubilisation von Polymeren durch Nicht-Ionische Tenside

Zusammenfassung Wasserunlösliche Copolymeren von Polyvinylalkohol-Azetat werden in wässerigen Lösungen nicht-ionischer Tenside optisch klar solubilisiert. Aus den Viskositätsmessungen ist zu schließen, daß sich die im Wasser eng gepackten Polymerenketten in den Tensidlösungen aufweiten. Die Trübungstemperatur der wässerigen Polymerenlösungen wird durch Zusatz der nicht-ionischen Tenside erhöht, doch ist der Effekt nicht so erheblich als durch Zusatz von ionischen Tensiden bei höheren Temperaturen. Die Lösungen von hydrophoben Polymeren und nicht-ionischen Tensiden zeigen andere Solubilisationsvermögen als die der Tensidlösungen allein. Diese Erscheinungen werden durch die Bindung der Tenside an die hydrophoben Teile der Polymeren oder, mit anderen Worten, durch Komplexbildung erklärt.

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Summary Some water-insoluble copolymers of polyvinylalcohol-acetate are solubilized transparently in aqueous solutions of non-ionic surfactants. From viscosity measurements it is concluded that the copolymer chains, which areshrunken in water, are uncoiled in the aqueous non-ionic surfactant solutions. Clouding points of the aqueous polymer solutions are increased by addition of the non-ionic surfactants, but the effect is less remarkable than by ionic surfactants, especially at higher temperatures.The mixed solution of a hydrophobic copolymer and a non-ionic surfactant has a solubilisation power which is different from that of the surfactant alone. These phenomena are explained by binding of the non-ionic surfactants to the hydrophobic parts of the copolymers, i. e., by the complex formation.

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