- Proton NMR and IR study of self-association in pyridylalkanols: Open or cyclic dimers? Higher polymers?
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1H NMR measurements indicate that (X-pyridyl)alkanols of the general formula (C5H4N)(CH2)nOH, where n = 1, 2 or 3, self-associate as open dimers, cyclic dimers, trimers and tetramers, with considerable variations depending on the position of the alkyl chain and its length. (X-Pyridyl)propan-2-ols behave like the corresponding pyridylmethanols with, however, somewhat lower association constants. The IR spectra of 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X = 3 or 4) in carbon tetrachloride suggest weak association, while the 2-pyridyl derivative occurs mainly as the intramolecularly hydrogen-bonded rotamer. The OH NMR shifts for the 3- and 4-pyridyl derivatives in benzene are concentration-dependent, but neither the equilibrium constants nor the degree of association can be evaluated. Benzyl alcohol in benzene associates as an open dimer and a cyclic tetramer, as does 2phenylpropan-2-ol, only more weakly. Rotation barriers for 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X = 2, 3 or 4) in DMSO or nitrobenzene are 20-21 kcal mol-1. Copyright
- Lomas, John S.,Adenier, Alain,Cordier, Christine
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p. 295 - 307
(2007/10/03)
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- Highly alkyl-selective addition to ketones with magnesium ate complexes derived from Gignard reagents
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(Chemical Equation Presented) A highly efficient alkyl-selective addition to ketones with magnesium ate complexes derived from Grignard reagents and alkyllithiums is described. The nucleophilicity of R in R3MgLi is remarkably increased compared to that of the original RLi or RMgX, while the basicity of R3MgLi is decreased. Furthermore, a highly R-selective addition to ketones is demonstrated using RMe2MgLi in place of R 3MgLi.
- Hatano, Manabu,Matsumura, Tokihiko,Ishihara, Kazuaki
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p. 573 - 576
(2007/10/03)
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- Kinetics of the self-assembly of α-cyclodextrin [2]pseudorotaxanes with 1,12-bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications in aqueous solution
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The kinetics and thermodynamics of the self-assembly of a series of [2]pseudorotaxanes comprised of α-cyclodextrin (α-CD) and racemic 1,12- bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications (L(CH2)12L2+) in aqueous solutions have been investigated using 1H NMR spectroscopy. The mechanism of assembly involves inclusion of the α-methyl- α-alkylmethanol substituent groups (-C(CH3)(OH)R, where R = Me, Et, Pr, Bu, allyl, and 4-butenyl) by α-CD, followed by a rate-determining passage of the cyclodextrin over the pyridinium group onto the dodecamethylene chain. Dicationic threads containing end groups with R = Ph or i-Pr or where L = 4- (α,α-diethylmethanol)-pyridinium did not form α-cyclodextrin pseudorotaxanes, even after prolonged heating. The trends in the rate and activation parameters may be related to the size, shape, and hydrophobicity of the alkyl substituents and are compared with several other systems from the literature. An increase in the length and hydrophobicity of the alkyl group increases the strength of end group inclusion and decreases the rate of threading. In addition, the presence of unsaturation in the alkyl substituent (allyl vs propyl and 4-butenyl vs butyl) results in an increase in the threading rate constant.
- Smith, A. Catherine,Macartney, Donal H.
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p. 9243 - 9251
(2007/10/03)
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- Pyridyl-propan-2-yl esters of 1-adamantane carboxylates
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Compounds having the general formula: STR1 wherein each of R 1 and R 2 independently represents hydrogen or alkyl of 1 to 4 carbon atoms;A represents --O-- or --CR 4 R 5, where R 4 and R 5 are defined as for R 1 or R 2 ;R 3 represents an adamantyl group; andPy represents a 3- or 4-pyridyl group, as free bases or their pharmaceutically acceptable salts are useful in treating androgen-dependent, especially prostatic, cancer.
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- 3- and 4-pyridylalkyl adamantanecarboxylates: Inhibitors of human cytochrome P450(17α) (17α-hydroxylase/C17,20-lyase). Potential nonsteroidal agents for the treatment of prostatic cancer
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Various 3- and 4-pyridylalkyl 1-adamantanecarboxylates have been synthesized and tested for inhibitory activity toward the 17α-hydroxylase and C17,20-lyase activities of human testicular cytochrome P450(17α). The 4-pyridylalkyl esters were much more inhibitory than their 3- pyridylalkyl counterparts. The most potent was (S)-1-(4-pyridyl)ethyl 1- adamantanecarboxylate (3b; IC50 for lyase, 1.8 nM), whereas the (R)- enantiomer 3a was much less inhibitory (IC50 74 nM). Nearly as potent as 3b was the dimethylated counterpart, the 2-(4-pyridylpropan-2-yl) ester 5 (IC50 2.7 nM), which was also more resistant to degradation by esterases. In contrast to their 4-pyridyl analogs, the enantiomers of the 1-(3- pyridyl)ethyl ester were similarly inhibitory (IC50 for lyase; (R)-isomer 8a 150 nM, (S)-isomer 8b 230 nM). Amides corresponding to the 4- pyridylmethyl ester 1 and the (S)-1-(4-pyridyl)ethyl ester 3b, respectively 11 and 15b, were much less inhibitory than their ester counterparts. On the basis of a combination of inhibitory potency and resistance to esterases, the ester 5 was the best candidate for further development as a potential nonsteroidal inhibitor of cytochrome P450(17α) for the treatment of prostate cancer.
- Chan, Ferdinand C. Y.,Potter, Gerard A.,Barrie, S. Elaine,Haynes, Benjamin P.,Rowlands, Martin G.,Houghton, John,Jarman, Michael
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p. 3319 - 3323
(2007/10/03)
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- Applications of Organolithium and Related Reagents in Synthesis. Part 3. A General Study of the Reaction of Lithium Alkyls with Pyridine Ketones
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The reaction of MeLi and PhLi with acetylpyridines (1a-c) and their annelated derivatives (2a), (2b), (3), and (4) has been examined.The 3- and 4-pyridyl ketones (1b), (1c), (3), and (4) gave similar results to acetophenone and 3,4-dihydronaphthalen-1(2H)-one.In the case of the 2-pyridyl ketones (1a), (2a), and (2b) unexpectedly low yields of products resulted from the addition of RLi to the carbonyl group; the reaction was efficiently enhanced by initially adding an additional amount of LiBr.These results were accounted for by the chelation of RLi or LiBr by the 2-pyridyl ketones.
- Epsztajn, Jan,Bieniek, Adam
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p. 213 - 220
(2007/10/02)
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- The Photo-initiated Substitution Reaction of 4-Chloropyridine and the Related 1-(4'-Pyridyl)-4-pyridone with Benzophenone in Aqueous 2-Propanol
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4-Chloropyridine (1) converts to 1-(4'-pyridyl)-4-pyridone (4) in aqueous 2-propanol.The photo-initiated reaction of both of these compounds in acidic and non-acidic 4:1 2-propanol/water with and without benzophenone is reported.
- Cosgrove, John P.,Vittimberga, Bruno M.
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p. 1277 - 1280
(2007/10/02)
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- Reactions of 2-Chloro-2-(4-pyridyl)propane with Nucleophiles. Substitution on Tertiary Carbon
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The reaction of 2-chloro-2-(4-pyridyl)propane (2) with lithium 2-propanenitronate affords the C-alkylation product 2-nitro-3-(4-pyridyl)-2,3-dimethylbutane (3), the Michael-adduct 2-nitro-2-methyl-4-(4-pyridyl)pentane (4), 4-isopropenylpyridine (5) and 2-
- Feuer, Henry,Doty,James K.,Kornblum, Nathan
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p. 783 - 787
(2007/10/02)
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