- Novel synthesis of 1-substituted-4-imidazolecarboxylates via solvent-free cycloaddition reaction between formamidines and isocyanides
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A simple and efficient protocol for cyclization between formamidines and ethyl isocyanoacetate has been described in the absence of metal catalyst and solvent. A series of 1-substituted-4-imidazolecarboxylates were synthesized in moderate to good yields with DABCO as base additive.
- Cao, Han,Bie, Fu-sheng,Liu, Xue-jing,Han, Ying,Ma, Jie,Shi, Yi-jun,Yan, Peng,Sun, Chao-yue,Wang, Hai-meng
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- Change of the favored routes of EI MS fragmentation when proceeding from N1, N1-dimethyl-N2-arylformamidines to 1,1,3,3-tetraalkyl-2-arylguanidines: Substituent effects
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Although series of N1, N1-dimethyl-N 2-arylformamidines and of 1,1,3,3-tetraalkyl-2-arylguanidines are structurally analogous and similar electron-ionization mass spectral fragmentationmay be expected, they display important differences in the favored routes of fragmentation andconsequently in substituent effectsonion abundances. In the caseof formamidines, the cyclizationelimination process (initiated by nucleophilic attack of the N-amino atom on the 2-position of the phenyl ring) and formation of the cyclic benzimidazolium [M-H]+ ions dominates, whereas the loss of the NR2 group ismore favored for guanidines. In order to gain information on the most probable structures of the principal fragments, quantum-chemical calculations were performed on a selected set. A good linear relation between log{I[M-H]+I [M]+?} and σR+ constants of substituent at para position in the phenyl ring occurs solely for formamidines (r = 0.989). In the case of guanidines, this relation is not significant (r = 0.659). A good linear relation is found between log{I[M-NMe2]+/I [M]+?} and σp+ constants (r = 0.993). Copyright
- Raczynska, Ewa D.,Makowski, Mariusz,Gal, Jean-Francois,Maria, Pierre-Charles
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p. 762 - 771
(2011/09/12)
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- Amidines. Part 31. pKa Values of N1,N1-Dialkyl-N2-phenylformamidines in Water-Ethanol Solutions
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The pKa values of three series (30 compounds in all) of N1,N1-dialkyl-N2-phenylformamidines (XC6H4N=CHNRR) have been measured in water-ethanol mixtures.The obtained pKa values of the amidines have been correlated with Hammett-type substituent constants and the pKa values of the corresponding primary amines determined in the same solvent.The applicability of various ? values is discussed and it is shown that, in each case, for substituents on the phenyl ring at the amino nitrogen atom ?0 values should be used.It is found that the slopes of regression lines for correlations with Hammett-type constants depend on the substituents at the amino nitrogen atom, as well as on the solvent.
- Oszczapowicz, Janusz,Jaroszewska-Manaj, Jolanta
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p. 1677 - 1680
(2007/10/02)
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- Amidines. Part 20. Rate of Reaction of N,N-Dialkylformamide Acetals with Substituted Anilines
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Rate of reaction of seven N,N-dialkylformamide acetals R2N-CH(OR2)2 with a series of anilines substituted on the phenyl ring have been measured in benzene, methanol, chloroform, and tetrahydrofuran by use of a g.l.c. method.In each case studied reaction is irreversible and obeys a second-order kinetic equation.Reaction rates correlate with Hammett ? constants for substituents on the phenyl ring of the aniline molecule.On the basis of the kinetic data, the mechanism of reaction is discussed.
- Osek, Jerzy,Oszczapowicz, Janusz,Drzewinski, Witold
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p. 1961 - 1964
(2007/10/02)
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- AMIDINES.PART XI. BASICITY OF N1,N1-DIMETHYLFORMAMIDINES
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The pKa values of twenty four N1,N1-dimethyl-N2-phenyl- and N1,N1-dimethyl-N2-alkyl-formamidines in 95.6percent ethanol (azeotrope) at 25+/-0.2 degC have been measured by the potentiometric method.The pKa values of N2-phenyl derivatives obey Hammett equation and obtained ρ value is ca. 2/3 of that for symmetrically disubstituted N,N'-diphenylformamidines.It is shown that there is a good correlation, common for both N2-alkyl as well as for N2-aryl formamidines between pKa values of dimethylformamidines and pKa of corresponding primary amines.The slope of this correlation line is also ca. 2/3 of that for symmetricall y disubstituted N,N'-dialkyl- and N,N'-diarylformamidines.Experimental conditions securing reliable results of pKa determinations by potentiometric method in ethanol are discussed.
- Oszczapowicz, Janusz,Raczynska, Ewa
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p. 419 - 428
(2007/10/02)
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- A Versatile New Synthesis of Quinolines and Related Fused Pyridines. Part 5. The Synthesis of 2-Chloroquinoline-3-carbaldehydes
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Acetanilides are converted into 2-chloroquinoline-3-carbaldehydes in good yield by the action of Vilsmeier's reagent in phosphoryl chloride solution.The reaction is shown to involve successive conversion of the acetanilide into an imidoyl chloride and then an N-(α-chlorovinyl)aniline.The latter enamine is diformylated at its β-position and subsequently cyclised to the chloroquinolinecarbaldehyde.The diformylated intermediates may be isolated in several cases and separately cyclised with polyphosphoric acid.
- Meth-Cohn, Otto,Narine, Bramha,Tarnowski, Brian
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p. 1520 - 1530
(2007/10/02)
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