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501.
A stereospecific route to -2,2-dimethyl-3-alkenyl-cyclopropanecarboxylic Acids is illustrated by a total synthesis of (±)--Chrysanthemic Acid (11). The key step consists of an alicyclic Claisen rearrangement of -silyl enolates derived from appropriately substituted ()-4-hexen-6-olides [e.g.(9)]. 相似文献
502.
C. R. Chen Randall L. Knight Lori Pollock 《Journal of polymer science. Part A, Polymer chemistry》1987,25(1):127-136
The radicals formed in poly(methyl methacrylate) (PMMA) under vacuum by UV irradiation at room temperature were carefully examined from 77 K to 300 K by electron spin resonance (ESR). The conventional nine-line spectrum was observed with significant overall intensity changes in contrast to previous reports. The intensity decreases greatly as the temperature increases from 77 K to 100 K. The intensity of the ESR spectrum increases as the temperature increases gradually from 100 K to 260 K. The spectral changes were reversible at all temperatures. Three different models are considered to interpret the temperature dependence of the intensity of the ESR spectrum. The results indicate that the ESR spectrum depends on (1) the steady-state concentration of the propagating radical in the polymer, (2) the conformational distributions of the radicals, and (3) the environmental structures of the polymer matrix. 相似文献
503.
Electrophilic amination of primary aliphatic and aromatic amines is reported using a diethylketomalonate-derived oxaziridine to afford the corresponding N-Boc hydrazines in good to excellent yields. The method allows a one-pot synthesis of pyrazoles from primary amines. [Reaction: see text] 相似文献
504.
Kinrade SD Schach AS Hamilton RJ Knight CT 《Chemical communications (Cambridge, England)》2001,(17):1564-1565
Silicon-29 NMR spectra of a neutral, dilute aqueous silicic acid solution, with a pH and Si concentration typical of soil solutions, reveal that a significant fraction of the silicon is incorporated in two five-coordinated organosilicon complexes when sodium gluconate is present. 相似文献
505.
Flourescence spectra have been observed from 1 and 5 torr of benzene after 504.2 nm excitation of the strongest two-photon band (linear polarization, ω1 = ω2) in the forbidden 260 nm 1B2u ← 1A1g absorption. The flourescence structure at 0.2 nm resolution is consistent with that expected from the fundamental ν′14 in the excited state. This confirms directly the previous assignments of the dominant two-photon absorption progression as 1no14Lo as well as the identity of the principal inducing mode, ν′14 (b2u). Vibrational relaxation from the level 141 appears similar to that observed from the one-photon levels. 相似文献
506.
Knight DA Delehanty JB Goldman ER Bongard J Streich F Edwards LW Chang EL 《Dalton transactions (Cambridge, England : 2003)》2004,(13):2006-2011
4-(1,4,7,10-Tetraazacyclotetradec-1-yl)methylbenzoic acid (cycmba, 1) has been synthesized, as a step towards the eventual development of sequence-specific hydrolytic complexes. A cobalt(III) complex of 1, [Co(cycmba)Cl2]Cl.1.5H2O (.1.5H2O) was found to be active against both an activated phosphodiester compound, bis(nitrophenyl)phosphate (BNPP), and supercoiled DNA. The presence of the benzoate group depresses the rate of hydrolysis of the ligand-Co(III) system at neutral pH, as confirmed by the kinetics results of a methyl ester analog. The ability of (2.1.5H2O) to bind to solid substrates and remain active was also demonstrated by attachment of the molecule to agarose beads. 相似文献
507.
O'Shaughnessy PN Gillespie KM Knight PD Munslow IJ Scott P 《Dalton transactions (Cambridge, England : 2003)》2004,(15):2251-2256
A group of chiral, dibasic, biaryl-bridged amido proligands containing peripheral methoxyphenyl (anisole) ligation are developed for the synthesis of new amide complexes of yttrium and lanthanum. A potentially tetradentate bis(amidoanisole) system gives, on reaction with [Y[N(SiMe(2)H)(2)](3)(THF)] a crystallographically-characterised bis complex [Y(H)] presumably as a result of low steric demand, since a more bulky version gives the target [Y[N(SiMe(2)H)(2)](THF)]. The molecular structure of the latter reveals a similar cis-alpha structure to our recently reported Schiff-base analogue. Variable-temperature NMR studies are consistent with low rigidity in the molecular structure. A potentially tridentate, amidoanisolyl/amido proligand gives complexes [M[N(SiMe(2)H)(2)](THF)(n)](M = Y, n= 1; M = La, n= 2). Chiral non-racemic versions of the above complexes were tested in the hydroamination/cyclisation of 2,2'-dimethylaminopentane to the corresponding pyrrolidine. Activities were relatively low compared to recently reported examples, and ee values were in the range 20-40% despite the well-expressed chirality of the catalysts. 相似文献
508.
509.
Robert D. Knight 《Journal of Geometry》2008,90(1-2):141-155
510.
High-resolution core-level photoemission and scanned-energy mode photoelectron diffraction (PhD) of the O 1s and N 1s states have been used to investigate the interaction of glycine with the rutile TiO2(1 1 0) surface. Whilst there is clear evidence for the presence of the zwitterion CH2COO− with multilayer deposition, at low coverage only the deprotonated glycinate species, NH2CH2COO is present. Multiple-scattering simulations of the O 1s PhD data show the glycinate is bonded to the surface through the two carboxylate O atoms which occupy near-atop sites above the five-fold-coordinated surface Ti atoms, with a Ti-O bondlength of 2.12 ± 0.06 Å. Atomic hydrogen arising from the deprotonation is coadsorbed to form hydroxyl species at the bridging oxygen sites with an associated Ti-O bondlength of 2.01 ± 0.03 Å. Absence of any significant PhD modulations of the N 1s emission is consistent with the amino N atom not being involved in the surface bonding, unlike the case of glycinate on Cu(1 1 0) and Cu(1 0 0). 相似文献