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Enantiomerically pure benzyl -α,β-epoxycarboxylates were prepared by a modified Darzens procedure utilizing aldol condensation reactions of chiral α-haloimidates with various aldehydes. A unique chirality reversal was observed using Zincenolates. 相似文献
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Salmanca Oviedo LN Gomez-Herrero A Landa Canovas AR Otero-Diaz LC 《Micron (Oxford, England : 1993)》2000,31(5):597-603
Two new misfit layer structures have been synthesized within the Sb-Nb-Se system. Powder X-ray diffraction and electron microscopy techniques (electron diffraction, HREM, XEDS) have been used to determine the nature of their structure. According to TEM and XEDS data (for more than 15 crystals studied) both phases are monolayer type, i.e. (SbSe)1+delta (NbSe2). Electron microscopy reveals a composite modulated structure that consists of the periodical intergrowth of a pseudotetragonal SbSe layer, denominated as Q, and a pseudohexagonal layer NbSe2, denominated as H. Both layers fit along b, stack along c and do not fit along a (misfit) giving rise to an incommensurate modulation along this direction. The two phases differ in the symmetry of the Q layers being in one case orthorhombic (for delta = 0.17) and monoclinic in the other (for delta = 0.19). After the characterization of the sample by electron microscopy the unit cells of the basic layers could be refined for both phases by powder X-ray diffraction: aQ = 5.824(2) A, bQ = 5.962(5) A, cQ = 23.927(6) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees and aH = 3.415(5) A, bH = 5.962(6) A,, cH = 11.962(1) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the orthorhombic phase; aQ = 5.844(2) A, bQ = 5.981(1) A, cQ = 23.919(5) A, alpha = 90 degrees, beta = 90 degrees and gamma = 96.00(3)degrees and aH = 3.439(1) A, bH = 5.994(2) A, cH = 11.956(3) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the monoclinic phase. The phase with the monoclinic Q-sublattice often appears as twinned crystals. The more abundant crystals are disordered intergrowths of both monolayer phases. 相似文献
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Lendon N. Pridgen 《Journal of heterocyclic chemistry》1980,17(6):1289-1291
Dichloro[1,3-bis(diphenylphosphino)propane]nickel(II) (dppp) was used as catalyst to prepare some previously unreported arylisoquinolines 3 , which were in turn hydrogenated to aryl-1,2,3,4-tetrahydroiso-quinolines 2 . This procedure is the most direct and efficient method currently available for the preparation of many compounds of the type 2 and 3 . 相似文献
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Shilcrat SC Mokhallalati MK Fortunak JM Pridgen LN 《The Journal of organic chemistry》1997,62(24):8449-8454
A new method is presented for the preparation of 1,2-disubstitued-1H-imidazole-5-carboxaldehydes by the reaction of N-monosubstituted amidines with 2-halo-3-alkoxy-2-propenals. The reaction is highly regioselective with ratios of 1,2,5:1,2,4-imidazolecarboxaldehydes ranging from 85:15 to 100:0. This methodology could be extended with similar results to the synthesis of imidazole-5-nitriles by the reaction of 2-bromo-3-methoxy-2-propenenitrile with N-monosubstituted amidines. 相似文献
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Susan C. Shilcrat David T. Hill Paul E. Bender Don E. Griswold Paul W. Drake S. Eggleston Ivan Lantos Lendon N. Pridgen 《Journal of heterocyclic chemistry》1991,28(5):1181-1187
A regiospecific synthesis of 6-phenyl-5-(4-pyridyl)-2,3-dihydroimidazo[2,1-b]thiazole ( 2 ) was accomplished by treatment of 6-phenyl-2,3-dihydroimidazo[2,1-b]thiazole ( 10 ) with the reactive complex of pyridine and ethyl chloroformate followed by oxidation with chromium(VI) oxide. Reaction of 4-phenyl-5-(4-pyridyl)imidazole-2-thione ( 12 ) with 1,2-dibromoethane in the presence of base also gave 2 together with its regioisomer 3 . The structures of 2 and 3 were confirmed by X-ray crystallography. Evaluation, on oral administration, in a one hour arachidonic acid-induced mouse ear inflammation assay, showed the inhibition of edema by 2 (48%) and 3 (34%) to be less than that of the 6-(4-fluorophenyl) analog 1 (SK&/F 86002) (69%), a known antiinflammatory agent. 相似文献
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Diastereomerically enriched N-(1,1-disubstituted methyl)(2 ‘-hydroxyl’-phenylethyl) amines were oxidatively converted to enantiomerically enriched primary disubstituted methylamines in excellent yields without racemization, using an improved lead tetraacerate (LTA) procedure. 相似文献
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Susan Shilcrat Ivan Lantos Michael Mcguire Lendon Pridgen Louisa Davis Drake Eggleston David Staiger Lee Webb 《Journal of heterocyclic chemistry》1993,30(6):1663-1671
The ethyl chloroformate salts of a variety of benzo-fused six membered π-deficient heteroaromatics, including quinoline, isoquinoline, 4-chloroquinoline, 3-bromoquinoline, phthalazine, and quinazoline, reacted with 6-aryl-2,3-dihydroimidazo[2,1-b]thiazole at the 5-position. The dihydroheteroaromatic adducts were oxidized by o-chloranil, sulfur, or electrochemical methodology to form the 5-heteroaromatic-6-aryl-2,3-dihydroimidazo[2,1-b]thiazoles, 10-15 . In each example, the regiochemistry of addition to the heteroaromatic ring was established. 相似文献