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41.
Edgar Heilbronner Evi Honegger Jacques Lecoultre Cyril A. Grob Raymond Houriet Eric Rolli 《Helvetica chimica acta》1986,69(8):2114-2126
The n ionization energies I and the gas-phase basicities GB of CH3-, Cl-, or CN-substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the n ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pKa values with either I or GB reveals that 2-substituted quinuclidines exhibit sizeable solvent-induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas-phase basicities. This agrees with earlier results concerning 2-substituted pyridines. 相似文献
42.
Christopher Batich Edgar Heilbronner Clayton B. Quinn John R. Wiseman 《Helvetica chimica acta》1976,59(2):512-522
Photoelectron spectroscopy has been used to examine the consequences of steric inhibition of conjugation in a distorted vinyl sulfide and vinyl ether. Based upon the degree of interaction a deviation from coplanarity of 70°–75° is calculated for 9-oxabicyclo[3.3.1]non-1-ene ( 3 ) and approximately 75°–80° for the sulfur analog 6 . 相似文献
43.
J.A. Edgar C.C.J. Culvenor P.A. Cockrum L.W. Smith Miriam Rothschild 《Tetrahedron letters》1980,21(14):1383-1384
Callimorphine, a putative pyrrolizidine alkaloid metabolite found in some Arctiid moths which feed as larvae on plants containing pyrrolizidine alkaloids, has been identified and synthesised. 相似文献
44.
Eric E. Boros James B. Thompson Edgar R. Wood O. Bradley McDonald Timothy D. Spitzer Andrea M. Sefler Bryan R. Reep 《Journal of heterocyclic chemistry》2004,41(3):355-358
5‐Methoxy and 5‐anilinopyrido[2,3‐d]pyrimidin‐7(8H)‐ones 2a‐2f were obtained by a tandem Michael addition‐cyclization reaction of methanol and anilines with pyrimidinylpropynoate 5. Methoxy derivative 2a was obtained in 62% yield by treatment of 5 with methanol and potassium carbonate. Anilino derivatives 2b‐2f were prepared in 31–71% yields by reacting 5 with the corresponding anilines in refluxing methanol. This methodology accomplishes Michael‐addition and pyridopyrimidinone ring formation in one‐pot and affords the desired products in reasonable yield without chromatography. Propynoate 5 did not react with 4‐cyanoaniline under these conditions. Reaction of 5 with 2‐aminopyridine gave the unexpected arylpyrido[2,3‐d]pyrimidinone 8 in 58% yield and reaction of 5 with imidazole afforded Michael‐adduct 9 in 69% yield. Compounds 2a and 5 were submicromolar inhibitors of epidermal growth factor receptor (EGFR) tyrosine kinase. 相似文献
45.
Hert J Willett P Wilton DJ Acklin P Azzaoui K Jacoby E Schuffenhauer A 《Journal of chemical information and computer sciences》2004,44(3):1177-1185
Fingerprint-based similarity searching is widely used for virtual screening when only a single bioactive reference structure is available. This paper reviews three distinct ways of carrying out such searches when multiple bioactive reference structures are available: merging the individual fingerprints into a single combined fingerprint; applying data fusion to the similarity rankings resulting from individual similarity searches; and approximations to substructural analysis. Extended searches on the MDL Drug Data Report database suggest that fusing similarity scores is the most effective general approach, with the best individual results coming from the binary kernel discrimination technique. 相似文献
46.
47.
Chlorocarbenium salts
-
of the Vilsmeier-Arnold type react with the silylated isocyanuric acid
to give 1-oxa-3-azabutatrienium salts
under mild conditions. From reactions of diarylchloromethenium salts
-
with
and ketones or tertiary carboxamides high yields of 2-azaallenium salts
were obtained. A few chloro substituted 2-azaallenium salts
were prepared from
and carbonyl compounds. The mechanisms of the new reactions are discussed. 相似文献
48.
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