Showing papers by "Alan R. Katritzky published in 1997"
77 citations
TL;DR: The pyridine rings result from tandem [3 + 3] annulations involving a Michael addition followed by cyclization as mentioned in this paper, which gives efficient and regioselective access to previously difficult to attain 3-unsubstituted pyridines.
Abstract: Base-promoted reactions of benzotriazolyl-containing acetic acid derivatives, 2-(benzotriazol-1-yl)acetonitrile (7a), 2-(benzotriazol-1-yl)acetamide (7b), and (±)-2-(benzotriazol-1-yl)propionamide (7c), with α,β-unsaturated ketones 8 give efficient and regioselective access to previously difficult to attain 3-unsubstituted pyridine derivatives: the 2-(substituted amino)pyridines 14a−k and the 4,6-substituted pyrid-2-ones 15a−h. The pyridine rings result from tandem [3 + 3] annulations involving a Michael addition followed by cyclization.
58 citations
TL;DR: In this paper, a general regiospecific method for the synthesis of (p-nitroaryl)diarylmethanes has been developed starting from diary lmethanols and 2-and/or 3-substituted nitrobenzenes.
Abstract: A general regiospecific method for the synthesis of (p-nitroaryl)diarylmethanes has been developed starting from diarylmethanols and 2- and/or 3-substituted nitrobenzenes. This utilizes the quantitative condensation between benzotriazole and diarylmethanols under acidic catalysis and in the presence of perfluorocarbon fluids, followed by vicarious nucleophilic substitution of the resulting diarylmethylbenzotriazoles upon nitrobenzenes in moderate to high yield. Oxidative nucleophilic substitution of hydrogen is observed as a side process. These vicarious nucleophilic substitutions complement Friedel−Crafts reactions for the synthesis of triarylmethanes.
55 citations
TL;DR: Intramolecular cyclization of the products, induced by acetic acid-hydrobromic acid or polyphosphoric acid (PPA), followed by simultaneous dehydration and debenzotriazolylation furnishes a wide range of polysubstituted naphthalenes 7a-f and of phenanthrenes 9 and 11 in moderate to good yields in one-pot procedures.
Abstract: (Benzotriazol-1-ylmethyl)benzenes and -naphthalenes 1a−f, easily accessible from benzyl bromides and benzotriazole, readily undergo lithiation and subsequent 1,4-addition to α,β-unsaturated aldehyd...
50 citations
TL;DR: Novel and facile routes to alkenyl, alkynyl, and aryl 1,2-diketones utilize treatment of benzotriazole derivatives with butyllithium and subsequent reaction with esters or acid chlorides to yield the substituted intermediates 2a−d, 8a,b, and 16a−g.
Abstract: Novel and facile routes to alkenyl, alkynyl, and aryl 1,2-diketones utilize treatment of benzotriazole derivatives 1, 7a,b, and 15a−d with butyllithium and subsequent reaction with esters or acid chlorides to yield the substituted intermediates 2a−d, 8a,b, and 16a−g. Reactions of the deprotonated 1 and 7 with α,β-unsaturated aldehydes followed by oxidation also produces similar intermediates 5 and 11a,b. Subsequent hydrolyses of the intermediates of type 2, 5, 8, 11, and 16 afford diverse 1,2-diketones in good yields.
39 citations
TL;DR: In this article, side chain elaboration of 2-(benzotriazol-1-ylmethyl)thiophenes 3a,b and 5g,j with styrenes in the presence of zinc bromide results in [3 + 2] cycloaddition to give in good yields.
Abstract: Diverse 2-(functionalized-alkyl)- and 2-alkenylthiophenes 2a,b, 4a,b, and 6a−d are prepared via the side chain elaboration of 2-(benzotriazol-1-ylmethyl)thiophenes 3a,b, themselves readily available from the condensation of 1-(hydroxymethyl)benzotriazole with thiophenes 1a,b. Treatment of 2-(benzotriazol-1-ylmethyl)thiophenes 3b and 5g,j with styrenes in the presence of zinc bromide results in formal [3 + 2] cycloaddition to give in good yields substituted cyclopent[b]thiophenes 16a/17a, 16b/17b, and 18. Lithiation and 1,4-addition to a variety of α,β-unsaturated ketones and aldehydes, and subsequent acid-catalyzed intramolecular cyclization followed by debenzotriazolylation−dehydration converts 3 and 5 to a range of polysubstituted benzo[b]thiophenes 19a−d and 25a−e in moderate to excellent yields. NOE difference spectroscopy and NMR 1H−13C long-range correlation support structures of types 19 and 25 and exclude those of type 26, thus confirming the cyclization pathway.
30 citations
25 citations
TL;DR: In this article, deuterium isotope effects on 13C chemical shifts have been measured for the enol and enaminone tautomers of a series of α-heterocyclic ketones.
Abstract: Deuterium isotope effects on 13C chemical shifts have been measured for the enol and enaminone tautomers of a series of α-heterocyclic ketones. Partial deuteration of the exchangeable hydrogen bound to the oxygen atom of the enol or the nitrogen atom of the enaminone leads to deuterium induced shifts of the 13C frequencies (2DIS) which are distinctive for the two types of structures. Thus, 9-methyl-2-phenacyl-1,10-phenanthroline, 2-pyridylacyl- and 2-phenacyl-quinazolines and 2-pyridylacyl- and 2-phenacyl-quinolines, which are known from independent evidence to exist in the enaminone structures, display large and variable negative 4DIS values, –240, –93, –126, –437 and –375, respectively, at the carbon bearing the oxygen atom. By contrast, 2-pyridylacyl- and 2-phenacyl-pyrazines, which are known to exist in the enol form, show large positive 2DIS values, 527 and 479, respectively, for the oxygen bound carbon atom.
23 citations
23 citations
TL;DR: Reactions of N,N'-disubstituted hydrazines with benzotriazole and aldehydes give N-(alpha-benzotrizoylalkyl)-N,N',disubStituted Hydrazines which on treatment with organometallic reagents form N-alkyl-N, N'-disubsubst ituted hydazines in good yields.
Abstract: Reactions of N,N'-disubstituted hydrazines with benzotriazole and aldehydes give N-(alpha-benzotriazoylalkyl)-N,N'-disubstituted hydrazines which on treatment with organometallic reagents form N-alkyl-N,N'-disubstituted hydrazines in good yields. N-(Benzotriazolylalkyl)-N,N'-disubstituted hydrazines and electron-rich olefins, in the presence of zinc bromide catalyst, generate N,N'-disubstituted pyrazolidines in moderate to good yields.
20 citations
TL;DR: Lithiated N-substituted 1,2,4-triazoles 3 and 8 and benzimidazole 11 reacted with (1R)-fenchone to give derivatives 5c, 9 and 12 in good yields as single diastereoisomers as mentioned in this paper.
Abstract: Lithiated N-substituted 1,2,4-triazoles 3 and 8 and benzimidazole 11 reacted with (1R)-fenchone to give derivatives 5c, 9 and 12 in good yields as single diastereoisomers. (S)-Lactic acid 16 reacted with o-phenylenediamine 15 to give optically pure (S)-2-(1-hydroxyethyl)benzimidazole17 (85%). Ring closures converted the fenchone derivative 12 into novel tricyclic fused benzimidazoles 13 and 14, and converted oxazolidine derivative 17 into compound 18 in yields of 50–70% as single diastereoisomers. Lithiated derivative 18 was alkylated to give compound 19 as a single diastereoisomer in high yield.
TL;DR: In this paper, benzotriazol-1-yl carbonyl chloride (BLC) was used to synthesize 1-(t-butoxy-benzyloxycarbonyl) and 1-(p-methoxy-bensyloxy-carbonyl)-benziotriazole (5) in good yields.
TL;DR: In this article, N-(α-Benzotriazol-1-ylalkyl)sulfonamides, readily available from benzotriaxol, an aldehyde and a sulfonamide, are converted into the corresponding N-(β-cyanoalkyl)-sulfoneamides in good yields by treatment with potassium cyanide.
TL;DR: Tosylmethylamines (1) are advantageous synthon equivalents for "nonstabilized" α-aminocarbanions of aromatic amines and clean reactions and high yields are observed provided one-step procedures are used as mentioned in this paper.
Abstract: Tosylmethylamines (1) are advantageous synthon equivalents for “nonstabilized” α-aminocarbanions of aromatic amines. Clean reactions and high yields are observed provided one-step procedures are ut...
TL;DR: In this article, 1-(primary alkyl)benzotriazoles were obtained in convenient yields by treating the corresponding alcohol with triphenylphosphine, N-bromosuccinimide, and benzotitriazole.
TL;DR: The first synthesisation of (α,α′-diperfluoroalkylated)diamines was reported in this paper together with a range of substituted α-perfluoro-alkylated amines all prepared in good yields from benzotriazole derivatives and perfluoroalky Grignard reagents in the presence of BF 3 ·Et 2 O.
TL;DR: A new general route to conjugated enynyl ketones was developed based on a two-step procedure involving palladium-catalyzed cross-coupling reactions of 1-(benzotriazol-1-yl)propargyl ethyl ether (3) and vinyl triflates or vinyl bromides.
Abstract: A new general route to conjugated enynyl ketones was developed based on a two-step procedure. First, palladium-catalyzed cross-coupling reactions of 1-(benzotriazol-1-yl)propargyl ethyl ether (3) and vinyl triflates or vinyl bromides afforded the key intermediates [1-(benzotriazol-1-yl)-1-enynyl]methyl ethyl ethers 5a-d in good yields. Then reactions of compounds 5 with primary halides gave intermediates 8, which were hydrolyzed by dilute acid to enynyl ketones 9a-g. Similar palladium-catalyzed coupling reactions of 3 with various aryl iodides followed by an analogous sequence afforded aryl-substituted propargyl ethers 12a-d and thence alkynyl ketones 13a,b.
TL;DR: The functionalized 1-benzylbenzotriazoles were derived from the lithiation of 1-(2,3-dimethoxybenzinzyl)benzolazole 2 followed by reactions with electrophiles, or from the condensation of benzyl alcohol 11 with benzotitriazole, undergo formal [3 + 2] cycloadditions with styrenes upon treatment with ZnBr2 to give functionalized indans.
TL;DR: In this paper, the authors proposed a new route to alkenyl, alkynyl, and aryl 1,2-diketones utilizing treatment of benzotriazole derivatives with butyllithium and subsequent reaction with esters or acid chlorides to yield the substituted intermediates 2a−d, 8a,b, and 16a−g.
Abstract: Novel and facile routes to alkenyl, alkynyl, and aryl 1,2-diketones utilize treatment of benzotriazole derivatives 1, 7a,b, and 15a−d with butyllithium and subsequent reaction with esters or acid chlorides to yield the substituted intermediates 2a−d, 8a,b, and 16a−g Reactions of the deprotonated 1 and 7 with α,β-unsaturated aldehydes followed by oxidation also produces similar intermediates 5 and 11a,b Subsequent hydrolyses of the intermediates of type 2, 5, 8, 11, and 16 afford diverse 1,2-diketones in good yields
TL;DR: In this paper, 1-(primary alkyl)benzotriazoles were obtained in convenient yields by treating the corresponding alcohol with triphenylphosphine, N-bromosuccinimide, and benzotitriazole.
Abstract: 1-(Primary alkyl)benzotriazoles are obtained in convenient yields by treating the corresponding alcohol with triphenylphosphine, N-bromosuccinimide and benzotriazole. Under these conditions, the alcohols gave exclusively the corresponding 1-alkyl-benzotriazoles. Allyl and propargyl alcohols also reacted regiospecifically in a typical Sn2 manner, and no products derived from prototropic rearrangement were found.
TL;DR: In this paper, N-(α-Benzotriazol-1-ylalkyl)sulfonamides, readily available from benzotriaxol, an aldehyde and a sulfonamide, are converted into the corresponding N-(β-cyanoalkyl)-sulfoneamides in good yields by treatment with potassium cyanide.
Abstract: N-(α-Benzotriazol-1-ylalkyl)sulfonamides, readily available from benzotriazole, an aldehyde and a sulfonamide, are converted into the corresponding N-(α-cyanoalkyl)sulfonamides in good yields by treatment with potassium cyanide.
TL;DR: In this paper, benzotriazol-1-yl carbonyl chloride (BLC) was used to synthesize 1-(t-butoxy-benzyloxycarbonyl) and 1-(p-methoxy-bensyloxy-carbonyl)-benziotriazole (5) in good yields.
Abstract: Benzotriazol-1-ylcarbonyl chloride, generated from benzotriazole and phosgene, reacts with t-butyl alcohol and p-methoxybenzyl alcohol to give 1-(t-butoxycarbonyl)benzotriazole (4) and 1-(p-methoxy-benzyloxycarbonyl)benzotriazole (5), respectively in good yields. The synthetic utility of reagents 4 and 5 is shown by effective amino protection in phenylalanine and phenylglycine.
TL;DR: In this paper, it was shown that N,N-Dimethylaminobenzotriazolyl carbene reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins in a one-pot procedure.
Abstract: N,N-Dimethylaminobenzotriazolylcarbene (5) reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins 10 in a one-pot procedure. It was also found that this novel carbene reacted with trans-dibenzoylethylene (11) in a [1+4] cycloaddition, generating 2-dimethylamino-3-benzoyl-5-phenylfuran (13) and 2-phenyl-3-[benzotriazol-1-yl]-4-benzoylfuran (14) whose structures were confirmed by 1H-13C long range correlations as well as the structure of furan 14 being confirmed by X-ray crystallography.
TL;DR: In this article, a convenient synthesis for 1-(mercaptomethyl)benzotriazole (89%) and its reactivity was examined, and the reaction was shown to be stable.
Abstract: A convenient synthesis is reported for 1-(mercaptomethyl)benzotriazole (89%) and its reactivity is examined.
TL;DR: In this paper, the tautomeric equilibrium constants for a series of aliphatic ketones in aqueous solution are quantitatively predicted using the quantum chemical self-consistent reaction field approach.
Abstract: The tautomeric equilibrium constants for a series of aliphatic ketones in aqueous solution are quantitatively predicted using the quantum chemical self-consistent reaction field approach.
TL;DR: (Benzotriazol-1-ylmethyl)benzenes and -naphthalenes 1a−f readily undergo lithiation and subsequent 1,4-addition to α,β-unsaturated aldehyd...
Abstract: (Benzotriazol-1-ylmethyl)benzenes and -naphthalenes 1a−f, easily accessible from benzyl bromides and benzotriazole, readily undergo lithiation and subsequent 1,4-addition to α,β-unsaturated aldehyd...
TL;DR: In this paper, deprotonated 1-(benzotriazol-1-yl)propargyl ethyl ethers react with propargyl, allyl and alkyl bromides to give the expected substituted derivatives 2, 4 and 9, respectively.
Abstract: Deprotonated 1-(benzotriazol-1-yl)propargyl ethyl ethers react with propargyl, allyl and alkyl bromides to give the expected substituted derivatives 2, 4 and 9, respectively. Subsequent eliminations of the benzotriazolyl group upon treatment with NaH or ZnBr2, and elaboration of the acetylene group, generate ethoxy substituted enediynes 3, 6, 8, dienynes 7 and enynes 12. Grignard reagents or LiAlH4 convert 9 into α-ethoxy substituted alkynes 10 and 11.