Showing papers by "Alan R. Katritzky published in 2002"
TL;DR: The melting points of several imidazolium-based ionic liquids or ionic Liquid analogues were correlated using the CODESSA program in order to develop predictive tools for determination of suitable ionic liquid salts.
Abstract: The melting points of several imidazolium-based ionic liquids or ionic liquid analogues were correlated using the CODESSA program in order to develop predictive tools for determination of suitable ionic liquid salts The data set consisted of melting point data (°C) for 104 substituted imidazolium bromides divided on the basis of the N-substituents into three subsets: A-57 compounds, B-29 compounds, and C-18 compounds The 45 benzimidazolium bromides form set D Five-parameter correlations were obtained for (i) set A with R2 = 07442, (ii) set B with R2 = 07517, and (iii) set D with R2 = 06899, while set C was correlated with a three parameter equation with R2 = 09432 These descriptors for predicting the melting points of the imidazolium and benzimidazolium bromides were based on the size and electrostatic interactions in the cations
188 citations
TL;DR: In an attempt to develop predictive tools for the determination of new ionic liquid solvents, QSPR models for the melting points of 126 structurally diverse pyridinium bromides in the temperature range 30-200 degrees C were developed with the CODESSA program.
Abstract: In an attempt to develop predictive tools for the determination of new ionic liquid solvents, QSPR models for the melting points of 126 structurally diverse pyridinium bromides in the temperature r...
163 citations
TL;DR: 1,3-Dipolar cycloaddition of organic azides 1, 2, or 3 to acetylenic amides 4 or 5 under solvent-free microwave irradiation produced the corresponding N-substituted C-carbamoyl-1,2, 3-triazoles 7a-12a in good to excellent yields.
Abstract: 1,3-Dipolar cycloaddition of organic azides 1, 2, or 3 to acetylenic amides 4 or 5 under solvent-free microwave irradiation produced the corresponding N-substituted C-carbamoyl-1,2,3-triazoles 7a-12a in good to excellent yields. Under similar reaction conditions, 1,3-dipolar cycloaddition of diazide 6 and acetylenic amide 4 gave the azido-triazole 13a.
83 citations
TL;DR: The empirical formula of Sepia MFA was calculated and used to estimate the number of protons in the aromatic region of the SepIA MFA polymeric chain and to suggest a possible monomeric unit profile.
Abstract: A 1 H nuclear magnetic resonance study of Sepia melanin, Sepia melanin free acid (Sepia MFA) and human hair melanin was carried out in deuterium oxide solution at pH 10-11. The empirical formula of Sepia MFA was calculated and used to estimate the number of protons in the aromatic region of the Sepia MFA polymeric chain and to suggest a possible monomeric unit profile.
68 citations
TL;DR: Whole-molecule descriptors are obtained computationally from molecular structures using a variety of programs in the areas of solubility, bioavailability, bio- and nonbio-degradability and toxicity.
Abstract: Whole-molecule descriptors are obtained computationally from molecular structures using a variety of programs. Their applications are reviewed in the areas of solubility, bioavailability, bio- and nonbio-degradability and toxicity.
66 citations
TL;DR: Unsymmetrical imidazolidines 10-14, optically active imidAZolidines 20-22, and 2,3-dihydro-1H-benzimidazoles 28 and 29 were synthesized in good to excellent yields by Mannich reactions of 1,2-ethanediamines 8a-c, 18a- c, or N-methyl-1,2 -benzenediamine (26a).
Abstract: Unsymmetrical imidazolidines 10-14, optically active imidazolidines 20-22, and 2,3-dihydro-1H-benzimidazoles 28 and 29 were synthesized in good to excellent yields by Mannich reactions of 1,2-ethanediamines 8a-c, 18a-c, or N-methyl-1,2-benzenediamine (26a) with benzotriazole and formaldehyde, followed by the nucleophilic substitution of the benzotriazolyl group with C-nucleophiles (Grignard reagents, sodium cyanide), an S-nucleophile (benzenethiol), and a P-nucleophile (triethyl phosphite).
51 citations
TL;DR: Two main structural factors which are strongly correlated with the HIV-1 protease inhibitory activity are revealed: molecular hydrophobicity and ability to form hydrogen bonds with the target enzyme.
50 citations
TL;DR: 3,4-Dihydro-2H-1,3-benzothiazines 4, 3,4,5-tetrahydro, 2,3, 4, 5-teticarbon-1-3- Benzothiazepines 6 were synthesized by directed ortho-lithiation of thiophenols and phenols and by side-chain lithiation of substituted thiopenols in one-pot.
Abstract: 3,4-Dihydro-2H-1,3-benzothiazines 4, 3,4-dihydro-2H-1,3-benzoxazines 9, and 2,3,4,5-tetrahydro-1,3-benzothiazepines 6 were synthesized by directed ortho-lithiation of thiophenols and phenols and by side-chain lithiation of substituted thiophenols, respectively, in one-pot by reacting with N,N-bis[(benzotriazol-1-yl)methyl]amines 3 as 1,3-biselectrophile synthons.
48 citations
TL;DR: Successive treatment of 3 with two different Grignard reagents in one-pot reaction led regiospecifically to N,N'-unsymmetrically substituted tetrahydroquinazoline derivatives 8a,b.
Abstract: 1-Benzotriazolylmethyl-3-propylhexahydropyrimidine (1) and 1,3-bis(1H-1,2,3-benzotriazol-1-ylmethyl)-1,2,3,4-tetrahydroquinazoline (3) were readily prepared by reactions of N-propyl-1,3-propanediamine or 2-aminobenzylamine with benzotriazole and formaldehyde, respectively. Intermediate 1 reacted with alkyl and aryl Grignard reagents to produce N,N'-unsymmetrically substituted hexahydropyrimidines 2a,b in 90 and 92% yields, respectively. Nucleophilic substitutions of 3 with Grignard reagents, allylsilane, and triethyl phosphite gave N,N'-disubstituted 1,2,3,4-tetrahydroquinazolines 4a-f, 5, and 6 in good to excellent yields. Successive treatment of 3 with two different Grignard reagents in one-pot reaction led regiospecifically to N,N'-unsymmetrically substituted tetrahydroquinazoline derivatives 8a,b.
36 citations
TL;DR: The chiral α-N-(tert-butoxycarbonyl)aminoacylbenzotriazoles ((N-Boc-amino-acyl)-benzotsarazoles) 3a−e are stable crystalline intermediates, easily prepared (61-88%) from N −Boc α-α amino acids.
Abstract: The chiral α-N-(tert-butoxycarbonyl)aminoacylbenzotriazoles ((N-Boc-aminoacyl)-benzotriazoles) 3a−e are stable crystalline intermediates, easily prepared (61-88%) from N-Boc-α-amino acids 1a−e. Compounds 3a−e react with achiral or chiral amines at 0-20 o C to give α-(N-Boc-amino)amides with no detectable racemization.
35 citations
TL;DR: In this article, an efficient conversion of carboxylic acids into Weinreb amides was achieved by treatment of N- acylbenzotriazoles 2a-i with N,O-dimethylhydroxylamine hydrochloride under mild conditions.
Abstract: Efficient conversions of carboxylic acids into Weinreb amides were achieved by treatment of N- acylbenzotriazoles 2a-i with N,O-dimethylhydroxylamine hydrochloride under mild conditions No racemization was found when optically active acids were employed
TL;DR: Models are reported for the prediction of the integrated UV absorbance for a diverse set of organic compounds using a quantitative structure-property relationship (QSPR) approach.
Abstract: High performance liquid chromatography (HPLC) with ultraviolet (UV) spectrophotometric detection is a common method for analyzing reaction products in organic chemistry. This procedure would benefit from a computational model for predicting the relative response of organic molecules. Models are now reported for the prediction of the integrated UV absorbance for a diverse set of organic compounds using a quantitative structure−property relationship (QSPR) approach. A seven-descriptor linear correlation with a squared correlation coefficient (R2) of 0.815 is reported for a data set of 521 compounds. Using the sum of ZINDO oscillator strengths in the integration range as an additional descriptor allowed reduction in the number of descriptors producing a robust model for 460 compounds with five descriptors and a squared correlation coefficient 0.857. The descriptors used in the models are discussed with respect to the physical nature of the UV absorption process.
TL;DR: The reactions of (2S)-2-amino-2-substituted-N-(4-nitrophenyl)acetamides 16a-c, succindialdehyde (13), and benzotriazole afforded enantiopure (3S,5R,7aR)-5-(1H-1,2,3-benzotrizol-1-yl)-3- substituting-1-(3-
Abstract: The reactions of (2S)-2-amino-2-substituted-N-(4-nitrophenyl)acetamides 16a−c, succindialdehyde (13), and benzotriazole afforded enantiopure (3S,5R,7aR)-5-(1H-1,2,3-benzotriazol-1-yl)-3-substituted-1-(4-nitrophenyl)tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones 17a−c, which were converted by sodium borohydride into (3S,7aR)-3-substituted-1-(4-nitrophenyl)tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones 18a−c. Chiral (2S)-2-amino-2-substituted-N-(4-methylphenyl)acetamides 12a−d, easily prepared in two steps from N-Boc-α-amino acids 10a−d, similarly reacted with glutaraldehyde (20) and benzotriazole to generate 5-benzotriazolyl-3-substituted-hexahydroimidazo[1,2-a]pyridin-2(3H)-ones 21a−d, which were converted by sodium borohydride directly into optically active 3-substituted-hexahydroimidazo[1,2-a]pyridin-2(3H)-ones 22a−d.
TL;DR: Dihydropyrrolo[2′,1′:3,4]pyrazino[2,1-a]isoindolones as discussed by the authors were obtained in 76-81% yields by the reaction of 2-(1H-pyrrol-1-yl)ethylamine with 2-formylbenzoic acids.
TL;DR: Wang resin linked amines were efficiently converted into amides using acylbenzotriazoles in 30-99% yields with good to excellent purities.
TL;DR: Reactions of organometallic reagents with 1-(substituted ethynyl)-1H-1,2,3-benzotriazoles 5 derived from a variety of benzotRIazolylmethyl ketones 3 afforded disubstituting acetylenes in synthetically useful yields.
Abstract: Reactions of organometallic reagents with 1-(substituted ethynyl)-1H-1,2,3-benzotriazoles 5 derived from a variety of benzotriazolylmethyl ketones 3 afforded disubstituted acetylenes in synthetically useful yields.
TL;DR: Di(benzotriazolyl)methanimine 1 was used for convenient preparation of previously unknown triazoles 11a,b and 15a-d and as a new reagent for the synthesis of oxadiazoles 17a-j as discussed by the authors.
Abstract: Di(benzotriazolyl)methanimine 1 was used for convenient preparation of previously unknown triazoles 11a,b and 15a-d and as a new reagent for the synthesis of oxadiazoles 17a-j.
TL;DR: Treatment of chiral diamines with benzotriazole and AlCl(3) led to enantiopure tricyclic 1,2,3,5,10,10a-hexahydroimidazo[1,5-b]isoquinolines 1a-c and 2,3-10, 10a-tetrahydroamides 15a-C via Lewis acid promoted iminium cation cyclizations.
Abstract: Condensations of chiral diamines 11a−c with benzotriazole and formaldehyde gave benzotriazolyl intermediates 12a−c; similar condensations of α-amino-amides 10a−c with benzotriazole and paraformaldehyde gave 14a−c. Subsequent treatment of 12a−c and 14a−c with AlCl3 led to enantiopure tricyclic 1,2,3,5,10,10a-hexahydroimidazo[1,5-b]isoquinolines 1a−c and 2,3,10,10a-tetrahydroimidazo[1,5-b]isoquinolin-1(5H)-ones 15a−c, respectively, via Lewis acid promoted iminium cation cyclizations.
TL;DR: In this article, the authors used CODESSA, GFA and CROMRsel methods for descriptor selection for predicting viscosities at 20 °C, and obtained a very good nonlinear MR model having five descriptors.
Abstract: Improved models for predicting viscosities at 20 °C were generated using three different methods for descriptor selection. Data set of 361 diverse organic molecules and their experimental viscosities were used for developing the models. Molecular properties are encoded by 822 initial descriptors computed by the CODESSA program. CODESSA, GFA and CROMRsel methods are capable of selecting good and facile viscosity models having only five descriptors. These methods are automated procedures for generation of simple multiregression (MR) models. All three methods produce excellent linear models, but the models obtained by the CROMRsel method are somewhat better. In addition, using the CROMRsel suite of programs a very good nonlinear MR model having five descriptors (two linear and three cross-product descriptors, R 2 = 0.908, S = 0.175) was obtained. Nonlinear models generated in this study show that the classical MR based methods can be efficiently used to obtain simple and very good nonlinear MR models. The best five-descriptor models selected in this study usually contain one geometrical (gravitational index) and one topological descriptor (Randic index of order 0), and three electrostatic descriptors which reflect the bonding properties of molecules, i.e. their capabilities to create (mainly) hydrogen bonds. Because of that, hydrogen-donors and hydrogen-acceptors surface areas, charges, total molecular surface areas, and maximum net atomic charges and state energies for oxygen atoms appear to be key factors for modeling the viscosity of organic molecules.
TL;DR: Refluxing an aldehyde with benzotriazole and benzyl carbamate in the presence of a catalytic amount of p-TsOH gave the corresponding benzyloxycarbonylamino-1-(1-benzotriaxolyl)alkane 2 in good yields.
Abstract: Refluxing an aldehyde 1 with benzotriazole and benzylcarbamate in the presence of a catalytic amount of p-TsOH gave the corresponding benzyloxycarbonylamino-1-(1-benzotriazolyl)alkane 2 in good yields. Compounds 2 treated with substituted tert-butyl acetates 3 using LDA as a base afford smoothly and under mild conditions the N-2-protected 3-aminoalkanoic esters 4.
TL;DR: Condensation reactions of benzotriazole and 2-(pyrrol-1-yl)-1-ethylamine with formaldehyde and glutaric dialdehyde afforded intermediates 2 and 6, which gave 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines 3a-e, 4, 5 and 5,6,9,10,11,11a-hexahydro-8H
Abstract: Condensation reactions of benzotriazole and 2-(pyrrol-1-yl)-1-ethylamine (1) with formaldehyde and glutaric dialdehyde, respectively, afforded intermediates 2 and 6. Subsequent nucleophilic substitutions of the benzotriazole group in 2 and 6 with Grignard reagents, sodium cyanide, and sodium borohydride gave 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines 3a-e, 4, 5 and 5,6,9,10,11,11a-hexahydro-8H-pyrido[1,2-a]pyrrolo[2,1-c]pyrazines 7a-c, 8, 9, respectively, in good yields.
TL;DR: Intermediates 2, 5, 8, 12 and 14 were obtained by cyclizations of dihaloalkanes with N-(benzotriazol-1-ylmethyl)heterocycles, 1-imidazol’s 1-yl methyl-5-phenyltetrazole in the presence of n-BuLi.
Abstract: N-(1-Cycloalkenyl)pyrroles 3a,b, -pyrazoles 6a,b, and -imidazoles 9a,b were synthesized via elimination of benzotriazole or 5-phenyltetrazole from the corresponding 1-[1-(heterocycyl)cycloalkyl]benzotriazoles 2, 5, and 8 or 1-[1-(heterocycyl)cyclohexyl]-5-phenyltetrazole (12 and 14). Intermediates 2, 5, 8, 12 and 14 were obtained by cyclizations of dihaloalkanes with N-(benzotriazol-1-ylmethyl)heterocycles, 1-imidazol-1-ylmethyl-5-phenyltetrazole (11), or 1-pyrazol-1-ylmethyl-5-phenyltetrazole (13) in the presence of n-BuLi.
Journal Article•
TL;DR: In this paper, a total of 397 natural and artificial comprehensively referenced sweeteners were classified by their structures into nine sets and the sweetness potencies were correlated with quantum chemical and other molecular descriptors using the heuristic and the best multi-linear regression methods of the CODESSA software package.
Abstract: A total of 397 natural and artificial comprehensively referenced sweeteners were classified by their structures into nine sets. The sweetness potencies were correlated with quantum chemical and other molecular descriptors using the heuristic and the best multi-linear regression methods of the CODESSA software package. QSPR models (two-parameter unless otherwise indicated) emerged for each subclass of sweeteners with R 2 values of 0.835 for 47 aldoximes, 0.959 for 8 acesulfamates, 0.919 for 9 sulfamates, 0.941 for 10 -arylsulfonylalkanoic acids, 0.715 for 27 guanidines (0.802 in a three-parameter correlation), 0.769 for 30 ureas/thioureas (0.888 in a three-parameter correlation), 0.905 for 20 natural sweeteners, 0.957 for 7 miscellaneous sweeteners (one-parameter correlation), 0.688 for 87 peptides (five-parameter correlation). A significant global five-parameter QSPR theoretical model with R 2 of 0.686 for the entire set of sweeteners is presented and discussed with reference to the possible existence of single or multiple sweetness receptors.
TL;DR: In this article, QSPR models for the melting points of 126 structurally diverse pyridinium bromides in the temperature range were developed for the determination of new ionic liquid solvents.
Abstract: In an attempt to develop predictive tools for the determination of new ionic liquid solvents, QSPR models for the melting points of 126 structurally diverse pyridinium bromides in the temperature r...
TL;DR: Reactions of benzyl bromide or benzyl cinnamate with N-(benzotriazol-1-ylmethyl)arylimidoyl chlorides in the presence of t-BuOK occur with opening of the benzotrizole ring affording 1,2,4-triazolo[1,5-a]quinoxalines.
Abstract: Reactions of benzyl bromide or benzyl cinnamate with N-(benzotriazol-1-ylmethyl)arylimidoyl chlorides (2a,b) in the presence of t-BuOK occur with opening of the benzotriazole ring affording 1,2,4-triazolo[1,5-a]quinoxalines (3a,b). A possible reaction mechanism is discussed.
TL;DR: The variable temperature (298 −179 K) NMR spectra of N-substituted 2-benzazepines correspond to two puckered mirror-image conformations, with a single chair-to-chair interconversion barrier for the benzazepine ring of ca. 11 kcal mol−1 in CD2Cl2 solution as discussed by the authors.
Abstract: The variable temperature (298–179 K)
1H NMR spectra of N-substituted 2-benzazepines (compounds 2–7) correspond to two puckered mirror-image (enantiomorphic) conformations, with a single chair-to-chair interconversion barrier for the benzazepine ring of ca. 11 kcal mol−1 in CD2Cl2 solution. A similar interconversion was detected for 1,3,4,5-tetrahydro-N-methylbenzazepine (compound 1), of lower symmetry. The conformations of compounds 1–7 were assigned on the basis of the magnitude of 1H-1H vicinal coupling constants. The 1H and 13C NMR spectral assignments were determined by 1H–1H COSY, 1H–13C COSY, and NOESY experiments.
TL;DR: 2, 4-Benzodiazepin-1-ones were prepared in moderate to good yields by reaction of bis(benzotriazolylmethyl)amines with ortho-metalated N-substituted benzamides.
Abstract: 2, 4-Benzodiazepin-1-ones were prepared in moderate to good yields by reaction of bis(benzotriazolylmethyl)amines with ortho-metalated N-substituted benzamides.
TL;DR: N,N-Bis(but-3-enyl)amines 5a-i were prepared in overall 74% yield from 1-(triphenylphosphoroylideneaminoalkyl)benzotriazole using an aza-Wittig reaction with aldehydes followed by a double Grignard reaction with allylmagnesium bromide.
Abstract: N,N-Bis(but-3-enyl)amines 5a-i were prepared in overall 74% yield from 1-(triphenylphosphoroylideneaminoalkyl)benzotriazole using an aza-Wittig reaction with aldehydes followed by a double Grignard reaction with allylmagnesium bromide. Use of vinyl or 1-propynylmagnesium bromide and allylmagnesium bromide in a sequential fashion also formed the expected doubly unsaturated amines 9a,b and 12, respectively.