Reaction of hydroxylamine with 5-aminooxazoles. A new route to isoxazoles

The nucleophilic attack of hydroxylamine at the 5 position of 2-aryl-4-trifluoroacetyl-5-amino-oxazoles leads to a mixture of stereoisomeric isoxazolines. Dehydration of these isomeric isoxazolines in the presence of trifluoroacetic anhydride gives 3-amino-4-acylamino-5-trifluoromethylisoxazoles. The structures and spectroscopic data of these compounds are discussed.     

Bildung siliciumorganischer Verbindungen. 89. Selektive Photobromierung von Si-methylierten Carbosilanen

Formation of Organosilicon Compounds. 89. Selective Photobromination of Si-methylated Carbosilanes A selective photobromination of the C atoms in the skeleton of Si-methylated carbosilanes is reported. (me₃Si? CH₂)₂Sime₂ reacts to me₃Si? CBr₂? Sime₂? CH₂? Sime₃ in good yields (me = CH₃); the second CH₂ group is considerably slower brominated. Photobromination of (me₂Si? CH₂)₃ consecutively yields a and b . Also from (me₂Si? CH₂)₄ the derivative with one CBr₂ group is accessible. Bromination of tertiary CH groups is highly preferred; this is shown by the selective formation of c . The C-bromination of SiBr-substituted carbosilanes is significantly more difficult; nevertheless (Brme₂Si)₂CH₂ selectively forms (Brme₂Si)₂CBr₂. Brme₂Si? CH₂? Sime₂? CH₂? Sime₃ forms Brme₂Si? CH₂? Sime₂? CBr₂? Sime₃, i. e., only the CH₂ group non-adjacent to SiBr is attacked. The formation of CHBr groups could not be detected. Higher temperatures and longer reaction times increase the formation of polymers.     

Bildung siliciumorganischer Verbindungen. LI. Reaktionen verschieden chlorierter 1,3,5-Trisila-cyclohexane mit CHMgCl und ihre 29SiNMR-Spektren

Formation of Organosilicon Compounds. LI. Reactions of Various Chlorinated 1.3.5-Trisilacyclohexanes with CH₃MgCl and their ²⁹SiNMR Spectra The reaction of (a) with meMgCl starts with the formation of a Grignard compound of (a) and forms (c) via (b). The reaction sequence will be described. The ring contraction of the six-membered ringsystem is also observed with compound (d) leading to (e), whereas (f) reacts to (g), the ringsystem being maintained. No ring-contraction is observed when investigating the reactions of the derivatives containing Si? H- and C? Cl-groups. Compound (i) gives rise to (j), (k) to (l) whereas cleavage occurs with (m) and (n) does not react under the conditions applied. According to the PMR and ²⁹SiNMR spectra, the polarity of the Si? Cl-bond decreases in the compounds containing Si? Cl and CCl-groups by increasing the number of CCl₂ groups. In the compounds containing Si? H and C? Cl-groups the polarity of the Si? H-bond increases with the degree of chlorination at the C-atom. By that, the different chemical behaviour can be understood. The preparations of the starting compounds are described.     

Simple enzyme reactors suitable for the byproduct-free preparation of the aglycones of naturally occurring glycosides under mild conditions

Naringinase from Penicillium species—containing α-l-rhamnosidase and β-d-glucosidase activity—immobilized on silicate carriers can be used as a mild and effective means to cleave naturally occurring glycosides into their aglycones and sugar components. The procedure was tested with flavonoid-, anthraquinone-, and steroidglycosides. Since the solubility of such compounds is limited in aqueous solutions, a simple batch procedure has been developed to convert solid substrates suspended in only small amounts of buffer to the desired products with high yields.     

Crystal violet combined with Merocyanine 540 for the ex vivo purging of hematopoietic stem cell grafts

The purpose of this study was to determine in a preclinical purging model, how effective crystal violet-mediated photodynamic therapy (CV-PDT) is against solid tumor and drug-resistant mutant tumor cells, and if certain limitations of CV-PDT can be overcome by using crystal violet (CV) in combination with the membrane-active photosensitizer, Merocyanine 540 (MC540). When used under conditions that preserved an adequate fraction of normal human granulocyte/macrophage progenitors (CFU-GM), CV-PDT failed to achieve meaningful reductions of DU145 prostate, H69 small cell lung cancer, and MDA-MB-435S breast cancer cells. Melphalan-resistant L1210/L-PAM1, adriamycin-resistant P388/ADR, and adriamycin-resistant HL-60/ADR leukemia cells were markedly less sensitive to CV-PDT than their wild-type counterparts, whereas cisplatin-resistant H69/CDDP cells were more sensitive than wild-type H69 cells. Sequential exposure to MC540- and CV-PDT under conditions that preserved an adequate fraction (73% and 29%, respectively) of normal CD34-positive hematopoietic stem cells and granulocyte/macrophage progenitors was highly effective against H69 (99.997% reduction) and H69/CDDP (99.999% reduction) cells, but ineffective against HL-60/ADR, MDA-MB-435S, and DU145 cells. CV thus shows only limited promise as a single-modality purging agent. However, in certain situations, clinically meaningful tumor cell depletions can be obtained by using CV in combination with a second photosensitizer such as MC540.     

Bildung siliciumorganischer Verbindungen. 70 [1]. Reaktionen Si-fluorierter 1,3,5-Trisilapentane mit CH3MgCl und LiCH3

Formation of Organosilicon Compounds. 70. Reactions of Si-fluorinated 1,3,5-Trisilapentanes with CH₃MgCl and LiCH₃ F₃Si? CCl₂? SiF₂? CH₂? SiF₃ 3 reacts with meMgCl. (me = Ch₃ starting with a Si-methylation and not with a C-metallation as in the corresponding Si- and C-chlorinated compounds, e. g. (Cl₃Si? CCl₂)₂SiCl₂ [2]. A CCl-hydrogenation is observed too, which in the case of F₃Si? CCl₂? SiF₂? CHCl? SiF₃ 4 gives meS₃Si? CCl₂? Sime₂? CH₂? Sime₃. (F₃Si? CCl₂)_{2 5} reacts with meMgCl to form preferentially 1,2-Disilapropanes by cleaving a Si? Cbond. The isolation of F₃Si? CCl₂H and meF₂Si? CCl₂? SiF₂me allows to locate the bond where 5 is cleaved at the beginning of the reaction. With meLi 5 reacts to form mainly me₃Si? C?C? Sime₃, showing that in the reaction of meLi, being a stronger reagent than meMgCl, and 5 a C-metallation occurs, following the same mechanism as in the reaction with (Cl₃Si? CCl₂)₂)SiCl₂ [2]. The reaction conditions for the synthesis of Si-fluroinated and C-chlorinated 1,3,5-Trisilapentanes in a 0.1 mol scale are reported. N.m.r. data of all investigated compounds are tabulated.     

Synthesis of aryleneisopropylidene polymers

Linear, high molecular weight aryleneisopropylidene (AIP) polymers have been synthesized via Friedel-Crafts alkylation reactions. Monomers such as p-bis-2-chloroiso-propylbenzene condense readily with arylene compounds of high electron density such as naphthalene and diphenyl ether. Catalytic amounts of tritylhexafluoroarsenate catalysts in combination with aluminum chloride and nitrobenzene direct the synthetic reactions towards a pure AIP structure. Side reactions which give polyindane structures through dimerization of p-bis(2-chloroisopropyl)benzene are eliminated when the polymerization temperature is kept below ?20°C. The preferred solvents are chlorinated compounds. A wide range of structural modifications and properties can be obtained by varying the monomer combinations. Desirable physical properties of AIP polymers include clarity, rigidity, impact toughness, oxidative stability, and resistance to stress cracking.     

Anion-exchange separation of metal ions in dimethyl sulphoxide-methanol-hydrochloric acid

The effect of dimethyl sulphoxide on the anion-exchange behaviour of many metals m a methanolic system with hydrochloric acid was explored. Distribution coefficients for 26 elements were determined in a mixed solvent system of dimethyl sulphoxide-methanol-0.6M hydrochloric acid, in which the proportions of dimethyl sulphoxide and methanoi were varied. Lead(II) and silver(I) complexes are soluble in this system. Interesting effects were noted for gold(III), iron(III), molybdenum(VI) and uranium(VI). As a measure of the usefulness of the systems studied, 27 anion-exchange separations of two- to four-component mixtures of metal ions were carried out, each with quantitative results.     

Zur Bildung von Disilylphosphino-Element-Verbindungen des C,Si, P

The Formation of Disilylphosphino-Element Compounds of C, Si, P The reactions of (me₃Si)₂PLi · OR₂ a (OR₂ = 1 monoglyme or 2 THF; me = CH₃) with CH₃Cl, CH₂Cl₂, ClCH₂CH₂Cl and ClCH₂? C₆H₅ give the compounds (me₃Si)₂Pme, (me₃Si)₂P? CH₂? P(Sime₃)₂, (me₃Si)₂P? CH₂CH₂Cl, (me₃Si)₂P? CH₂CH₂? P(Sime₃)₂ and (me₃Si)₂P? CH₂C₆H₅ respectively. In the same manner a reacts with me₂SiCl₂ in a molar ratio 1:1 to (me₃Si)₂P? Sime₂Cl and in a molar ratio 2:1 to (me₃Si)₂P? Sime₂? P(Sime₃)₂ b . The compound b decomposes to [me₃SiP? Sime₂]₂ and (me₃Si)₃P at 220°C. In the reactions of a with ClP(C₆H₅)₂ and ClPme₂ the compounds (me₃Si)₂P? P(C₆H₅)₂ and (me₃Si)₂P? Pme₂, respectively, are obtained. a reacts with HgCl₂ to (me₃Si)₂P? P(Sime₃)₂. (me₃Si)₃P can be cleaved with ClP(C₆H₅)₂ and ClPme₂ yielding (me₃Si)₂P? P(C₆H₅)₂ and (me₃Si)₂P? Pme₂, respectively. The ¹H- and ³¹P-n.m.r. and mass spectroscopic data are reported.