The oxidation of adamantane with an iron salen complex modelling ω-hydroxylase

An interesting regioselectivity (high secondary selectivity) was observed in the oxidation of adamantane in the presence of (FeSalen) ₂O, 2-mercapto-ethanol, pyridine, and oxygen, giving 1-adamantanol (67 % based on the catalyst used), 2-adamantanol (162 %) and 2-adamantanone (51 %) for a typical example. The yield of each product was dependent on the reaction conditions especially on the mercaptan concentration. This high secondary selectivity (product ratio, 3.2 : 1) and the predominant formation of 2-adamantanol is unique and quite different from those (ca 1 : 1 mostly adamantanone/1-adamantanol) of autoxidation. This is the first successful ω-hydroxylase model.     

Unimolecular metastable decompositions of gem-dimethoxyalkanes (RR'C(OCH(3))(2)) upon electron impact. I. Dimethoxymethane and 1, 1-dimethoxyethane

The unimolecular metastable decompositions of dimethoxymethane (CH(2)(OCH(3))(2), 1) and 1,1-dimethoxyethane (CH(3)CH(OCH(3))(2), 2) upon electron impact have been investigated by means of mass-analyzed ion kinetic energy (MIKE) spectrometry, collision-induced dissociation (CID) spectrometry and D-labeling techniques. Both molecular ions are formed at extremely low abundance. Sequential transfers of a methyl group and a hydrogen atom to an ether oxygen are observed during the decomposition of [M - H](+) ions from 1 and 2. The [M - H](+) ion from 2 also decomposes into the m/z 43 ion by the loss of dimethyl ether. Almost complete hydrogen exchange is observed prior to the loss of CH(4) from the m/z 45 ion ([M - OCH(3)](+)) of 1. The m/z 59 ions ([M - OCH(3)](+)) of 2 decompose competitively into the m/z 31 and 29 ions by the losses of C(2)H(4) and CH(2)O, respectively. The former loss occurs via two different fragmentation pathways. The relative abundances of the ions in the MIKE spectra increase with decreases in the total heat of formation (Sigma DeltaH(f)) of the ion plus the neutral fragment. Copyright 2000 John Wiley & Sons, Ltd.     

Sequencing wasp venom peptides by endopeptidase digestion and nested collision-induced dissociation/post-source decay methods

A method incorporating nested collision-induced dissociation/post-source decay (CID/PSD) combined with endopeptidase digestion is described as an approach to determine the sequence of N-terminally modified peptides. The information from immonium and related ions observed in the CID/PSD spectrum was used for the selection of a suitable endopeptidase for the digestion of peptides. Rapid and reliable assignment of peptide sequence was performed by the comparison of CID/PSD spectra of both intact and endopeptidese-digested peptide fragments, since the assignments of the observed fragment ions to either N- or C-terminal ions can thus be carried out unambiguously. This nested CID/PSD method was applied to the sequence determination of two peptides from the solitary wasps Anoplius samariensis and Batozonellus maculifrons (pompilid wasps), which could not be sequenced by the Edman method due to N-terminal modification.     

delta-[Ru(acac)(2)L] (L = a mesogenic derivative of bpy) as a novel chiral dopant for nematic liquid crystals with large helical twisting power

The helical twisting power of a chiral ruthenium complex Delta-[Ru(acac)2L], in which L (mesogenic ligand) and acac denote 5,5'-(4-octylphenyloxycarbonyl)-2,2'-bipyridyl and acetylacetonate, respectively, was determined to be betaM = -71 and -1.8 x 102 mum-1 in room-temperature nematics ZLI-1132 and MBBA, respectively.     

Novel superstructure of nondiscoid mesogens: uneven-parallel association of half-disk molecules, 3,4,5-trialkoxybenzoic anhydrides, to a columnar structure and its one-directionally geared interdigitation

Compact and simple nondiscoid mesogens, trialkoxybenzoic anhydrides 2-11 ((RO)(3)C(6)H(2)-CO-O-CO-C(6)H(2)(OR)(3), R = C(2)H(5), n-C(3)H(7), n-C(4)H(9), n-C(6)H(13), n-C(8)H(17), n-C(10)H(21), n-C(12)H(25), n-C(14)H(29), n-C(16)H(33), and (S)- and (R)-3,7-dimethyloctyl) were designed and synthesized, and their superstructures were investigated by polarized light microscopy, differential scanning calorimetry, calculation (MM2 and AM1), circular dichroism spectroscopy, and X-ray diffraction. As the result, in the cases of 5-9 and 11, the half-disk molecules in the liquid crystal phases were self-assembled by the dipole-dipole interaction between their carbonyl groups to a column in which the molecules were piled up in an alternately antiparallel manner, and the columns were interdigitated each other. The observed interdigitations were highly directional in the perpendicular direction to the column axis. In the case of compound 11 which has (S)- or (R)-3,7-dimethyloctyl groups, a helical organization of the molecules in the column was estimated from the peaks in the circular dichroism spectra. This is the first report of a one-directionally interdigitated columnar phase, and these compounds are the first liquid crystalline acid anhydrides. It was demonstrated that a -CO-O-CO- moiety is useful as a polar junction in liquid crystalline compounds.     

Thiamin ylide: isolation and identification

The action of two equivalents of NaOEt on thiamin hydrochloride in EtOH gives a neutral compound. Spectroscopic data and its chemical behavior indicated that the compound is thiamin ylide $\text{1}$. The chemical behaviors of $\text{1}$ are entirely consistent with those of in situ generated thiamin ylide.     

Radical polymerization of allyl alcohol and allyl acetate

Monoallyl compounds are not readily homopolymerized by a conventional free‐radical mechanism. However, the polymerization of allylbiguanide hydrochloride was reported to proceed in a concentrated solution of hydrochloric or phosphoric acid in the presence of a radical initiator. Here we have studied the polymerization of allyl alcohol by a radical initiator in the presence of a Lewis acid (ZnCl₂, CuCl₂ or MgCl₂) in an organic solvent (toluene, hexane, methanol or isopropanol). Reactions were performed either at room temperature or 50°C under an atmosphere of nitrogen or in a sealed tube. The same polymerization was also carried out in water and in a concentrated acid solution. The polymer product was purified by dialysis in 0.2–3.7% yield and confirmed by elemental analysis, infrared spectroscopy and ¹H NMR. The molecular weight range of poly(allyl alcohol) was 10,000–35,000. The polymerization of allyl acetate by the radical initiator under the above conditions gave poly(allyl acetate) with the molecular weight range of 10,000–13,800 by multi‐angle laser light scattering. Copyright © 2007 John Wiley & Sons, Ltd.     

Reactivity of positively charged cobalt cluster ions with CH4, N2, H2, C2H4, and C2H2

Reactivity of positively charged cobalt cluster ions (Co _n ⁺ ,n=2?22), produce by laser vaporization, with various gas samples (CH₄, N₂, H₂, C₂H₄, and C₂H₂) were systematically investigated by using a fast-flow reactor. The reactivity of Co _n ⁺ with the various gas samples is qualitatively consistent with the adsorption rate of the gas to cobalt metal surfaces. Co _n ⁺ highly reacts with C₂H₂ as characterized by the adsorption rate to metal surfaces, and it indicates no size dependence. In contrast, the reactions of Co _n ⁺ with the other gas samples indicate a similar cluster size dependence; atn=4, 5, and 10?15, Co _n ⁺ highly reacts. The difference can be explained by the amount of the activation energy for chemisorption reaction. Compared with neutral cobalt clusters, the size dependence is almost similar except for Co ₄ ⁺ and Co ₅ ⁺ . The reactivity enhancement of Co ₄ ⁺ and Co ₅ ⁺ indicates that the cobalt cluster ions are presumed to have an active site for chemisorption atn=4 and 5, induced by the influence of positive charge.     

Chiral phosphine oxide BINAPO as a Lewis base catalyst for asymmetric allylation and aldol reaction of trichlorosilyl compounds

Chiral phosphine oxide BINAPO, which was readily prepared from chiral phosphine BINAP, exhibited good catalytic activities in the reaction of trichlorosilyl compounds via hypervalent silicate intermediates. The allylation of aldehydes with allyltrichlorosilanes in the presence of a catalytic amount of BINAPO gave the allylated adducts in good enantioselectivities (up to 79% ee) wherein a combination of diisopropylethylamine and tetrabutylammonium iodide as additives was crucial to accelerate the catalytic cycle. ³¹P NMR analysis of the phosphine oxide suggested that the amine promoted the dissociation of phosphine oxide from silicon atom. BINAPO also promoted the enantioselective aldol reaction of aldehydes with trichlorosilyl enol ethers in the presence of diisopropylethylamine as an additive to afford the corresponding aldol adducts in high diastereo- and enantioselectivities (up to syn/anti=1/25, 96% ee (anti)).