Structural revision in the reactions of 3-cyanochromones with primary aromatic amines. Improved synthesis of 2-amino-3-(aryliminomethyl)chromones

3-Cyanochromones react with primary aromatic amines to give 2-amino-3-(aryliminomethyl)chromones as the sole products or as their mixtures with Z- and E-3-anilino-2-salicyloylacrylonitriles, depending on the reaction conditions. With aliphatic amines, 2-amino-3-(alkyliminomethyl)chromones are obtained in good yields. The reaction of 3-cyanochromone with o-phenylenediamine is reinvestigated and proof for the product structure and a possible reaction pathway are presented.     

Chemoselective synthesis of 3H-pyrrolo[2,3-c]quinolin-4(5H)-one derivatives from 3-phenacylideneoxindoles and substituted tosylmethyl isocyanide (TosMIC)

A simple and convenient synthetic approach to access of 3H-pyrrolo[2,3-c]quinolin-4(5H)-one derivatives by the reaction of (Z)-3-(2-oxo-2-ethylidene)indolin-2-one derivatives 1 with functionalized TosMICs under basic conditions has been reported. The desired products were obtained in good to excellent yields (82–94%). The easy accessibility of the starting materials, simple and mild reaction conditions, short reaction time, and good to excellent chemical yields make this methodology highly efficient.     

Synthesis of dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylates via a one-pot and four-component reaction

A number of new dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylate derivatives have been prepared regiospecifically in moderate to good yield from the cyclocondensation reaction of dialkyl (E)-2-(dialkoxyphosphoryl)-3-(aroyl)-2-butenedioate, derived from the reaction between trimethyl phosphite, an acetylenic ester, and an aroyl chloride, with phenylhydrazine. The reaction is four-component and is carried out under reflux conditions in dry toluene.     

anti-Selective aldol reactions of chiral alcohol substituted γ-benzyloxyl vinylogous urethanes and the synthesis of 3-benzyloxyl-4-hydroxylalkan-2-ones

The anti-selective aldol reaction of chiral alcohol-substituted γ-benzyloxy vinylogous urethanes is described. The use of (1S,2R,4R)-1-(hydroxydiphenylmethyl)-7,7-dimethylbicyclo[2,2,1]-heptan-2-ol as a chiral auxiliary in the aldol reaction of a vinylogous urethane enolate was found to provide anti-products in good yields with moderate to excellent enantioselectivities. The major anti-vinylogous urethane lactones were transformed into 3-benzyloxyl-4-hydroxylalkan-2-ones in good yields.     

Bromophilic substitution/carbophilic substitution cascade reactions of α,α-dibromo-2-methoxyacetophenone with C-, N- and O-nucleophiles

α,α-Dibromo-2-methoxyacetophenone reacts, under mild reaction conditions, with C-, N- and O-nucleophiles via a bromophilic substitution/protonation/carbophilic substitution cascade process to afford α-monosubstituted-2-methoxyacetophenones in moderate to good yield. The only exception from this reaction pathway is the reaction with the anion derived from malononitrile in which 2-aroyl-1,1,3,3-tetracyanopropene is obtained.     

Copper promoted C-S and C-N cross-coupling Reactions:The synthesis of 2-(N-Aryolamino)benzothiazoles and 2-(N-Aryolamino)benzimidazoles

The synthesis of 2-(N-aryolamino)benzothiazoles and 2-(N-aryolamino)benzimidazoles has been accomplished in the presence of copper catalyst. These reactions involve C-S and C-N cross-coupling reaction. All electron donating and withdrawing substituent's readily underwent the reaction to give target products in good to excellent yield. In addition, the reaction also gave target product in high yield with bulk scale.     

A novel intramolecular Ugi 3CC for the synthesis of N-alkyl-3-oxo-2-aryl-1,2,3,4-tetrahydropyrazino[1,2-a]indole-1-carboxamides

An intramolecular Ugi reaction of 2-(2-formyl-1H-indol-1-yl)acetic acid with aryl amines and isocyanides has been developed to produce a novel class of N-alkyl-3-oxo-2-aryl-1,2,3,4-tetrahydropyrazino[1,2-a]indole-1-carboxamides in good yields. This is the first report on intramolecular Ugi three component reaction of 2-(2-formyl-1H-indol-1-yl)acetic acid, aryl amine, and isonitrile.     

An efficient route to coumarin derivatives under dual catalysis,an organo- and a Lewis acid catalyst

An efficient reaction of dialkyl acetylenedicarboxylate with various o-hydroxy aromatic aldehydes under dual catalysis with piperidine and FeCl₃ in refluxing toluene afforded alkyl 2-oxo-2-(2-oxo-2H-chromen-3-yl) acetates in good to excellent yield. The advantages of this reaction include the use of easily available starting materials, one-pot reaction, mild reaction conditions and operational simplicity.     

Stereoselective synthesis of (E)-α-aryltellurenylvinylsilanes via hydromagnesiation reaction of alkynylsilanes

(E)-α-Aryltellurenylvinylsilanes have been synthesized stereoselectively via the hydromagnesiation of alkynylsilanes, followed by the reaction with aryltellurenyl iodides. (E)-α-Aryltellurenylvinylsilanes can undergo the cross coupling reaction with Grignard reagents in the presence of Ni(PPh₃)₂Cl₂ catalyst to afford (Z)-1,2-disubstituted vinylsilanes in good yields.     

Solid-phase synthesis of 2-imidazolidinethiones via Mitsunobu reaction of N-(2-hydroxyethyl)thioureas

This letter reports the solid-phase synthesis of 2-imidazolidinethiones via the N-cyclization of N-(2-hydroxyethyl)thioureas using the Mitsunobu reaction in good yield and purity. This process employed the reductive amination of an ArgoGel-MB-CHO resin to anchor the aminoalcohols, followed by a reaction with isothiocyanates to give the resin-attached N-(2-hydroxyethyl)thioureas. Cleavage of the 2-imidazolidinethiones was performed with trifluoroacetic acid.     

Insights for diastereoselective synthesis of cyclic α-sulfinyl and sulfanyl oximes

The comparison in several reaction conditions for synthesis of nonracemic α-methylsulfinylation of 3,4-dihydronaphthalen-1(2H)-one was achieved. The sulfanylation reactions of 3,4-dihydronaphthalen-1(2H)-one-O-methyloxime and 2-(methylsulfinyl)-3,4-dihydronaphthalen-1(2H)-one-O-methyloxime by homogenous reaction medium are reported. The products were obtained in good yields and de. The yields, diastereoselectivity and theoretical calculations to all obtained compounds to support the experimental data are compared and discussed.     

Synthesis of new pyrazole-1,2,3-triazole dyads

An efficient two step synthetic methodology of new 5(4)-aryl-4(5)-[3(5)-(2-hydroxyphenyl)-1H-pyrazol-5(3)-yl]-1H-1,2,3-triazole dyads was established. The reaction of (E)-2-styryl-4H-chromen-4-ones, used as building blocks, with sodium azide, gave 4(5)-aryl-5(4)-(chromon-2-yl)-1H-1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their styryl moiety which upon reaction with hydrazine hydrate afforded the expected pyrazoles in moderate to very good yields.     

Synthesis of (Z)-1-benzylidene-3-(1H-indol-1-yl)-1H-indene-2,2(3H)-dicarbonitriles via three-component reaction of 2-alkynylbenzaldehyde, malononitrile, and indole

Three-component reaction of 2-alkynylbenzaldehyde, malononitrile, and indole under mild conditions is described, which generates the desired (Z)-1-benzylidene-3-(1H-indol-1-yl)-1H-indene-2,2(3H)-dicarbonitriles in moderate to good yields. This reaction proceeds smoothly with high selectivity. The tandem condensation, nucleophilic addition, and 5-exo-cyclization may be involved in the process.     

Four-component tandem protocol for the stereoselective synthesis of highly functionalized [1,4]-thiazines

The one-pot, four-component tandem reaction of ethyl 2-[(2-oxo-2-arylethyl)sulfonyl]acetate/ethyl 2-[(2-ethoxy-2-oxoethyl)sulfonyl]acetate, an aromatic aldehyde and pyrrolidine provides a rapid and facile access to new ethyl 3-aroyl-1-benzyl-2,2-dioxo-4-aryloctahydro-2-pyrrolo[2,1-c][1,4]thiazine-1-carboxylates/diethyl 1-benzyl-2,2-dioxo-4-aryloctahydro-2-pyrrolo[2,1-c][1,4]thiazine-1,3-dicarboxylates. This reaction shows high stereoselectivity and proceeds in good yields.     

Regioselective synthesis of fused pyrazolo[1,5-a]pyrimidines by reaction of 5-amino-1H-pyrazoles and β-dicarbonyl compounds containing five-membered rings

Reactions of 3-substituted-5-amino-1H-pyrazoles with 2-acetylcyclopentanone or 2-ethoxycarbo-nylcyclopentanone lead to the regioselective formation of a new series of cyclopentapyrazolo[1,5-a]pyrimidines in good yields. When 2-acetylbutyrolactone was used, the reaction provided 6-(2-hydroxyethyl)pyrazolo[1,5-a]pyrimidinone and/or the intermediate (3Z)-3-{1-[(5-R-1H-pyrazol-3-yl)amino]ethylidene}-4,5-dihydrofuranone. This indicates that the cyclization proceeds with butyrolactone ring opening as the last step. Several aspects of this regioselective reaction, including mechanistic and structural studies, are considered.     

(l)-Proline-catalysed novel tandem reactions of 1-substituted piperidin-4-ones with (E)-4-arylbut-3-en-2-ones: N-substituent mediated product selectivity and synthesis of novel nitrogen heterocycles

(l)-Proline-catalysed reaction of 1-alkyl/aralkylpiperidin-4-ones with (E)-4-arylbut-3-en-2-ones furnishes novel isoquinoline derivatives, with two or three rings, in good yields via tandem Robinson annulation-Michael addition(s) sequences, while the reaction of 1-arylpiperidin-4-ones with (E)-4-arylbut-3-en-2-ones affords 3-azabicyclo[3.3.1]nonan-9-ones via a tandem Michael addition-aldol reaction sequence.     

A new route towards N-(α-methoxybenzyl)aziridines

A new synthesis of N-(α-methoxyarylmethyl)-2,2-dimethylaziridines is presented. Different benzaldehydes were converted into the corresponding imines upon reaction with 2-bromo-2-methylpropylamine. Treatment of the latter imines with sodium methoxide afforded N-(α-methoxyarylmethyl)-2,2-dimethylaziridines in good yields.     

AlCl3-mediated tandem Friedel-Crafts reactions of vinylidenecyclopropanes with acyl chlorides: a facile synthetic method for the construction of 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives

AlCl₃-mediated tandem Friedel-Crafts reaction of vinylidenecyclopropanes with acyl chlorides produced the corresponding 1-[2-(2,2-diarylvinyl)-1-phenyl-3H-inden-5-yl]ethanone derivatives in moderate to good yields under mild conditions within short reaction time.     

Nucleophilic phosphine-catalyzed [3+2] cycloaddition of allenes with N-(thio)phosphoryl imines and acidic methanolysis of adducts N-(thio)phosphoryl 3-pyrrolines: a facile synthesis of free amine 3-pyrrolines

In this report, the dipolarophile imines with easily removable activating group O,O-diethyl(thio)phosphoryl have been investigated in the nucleophilic phosphine-catalyzed [3+2] cycloaddition reaction of electron-deficient allenes. Under the catalysis of a tertiary phosphine, N-(thio)phosphorylimines readily undergo the [3+2] cycloaddition reaction with ethyl 2,3-butadienoate or ethyl 2,3-pentadienoate, affording the corresponding N-(thio)phosphoryl 3-pyrrolines in moderate to high yields with good diastereoselectivity. Removal of the (thio)phosphoryl group from the adducts has been successfully achieved via the acidic methanolysis of the P-N bond, giving the free amine 3-pyrrolines in fair to good yields without severe aromatization. Thus, a facile synthesis of N-unsubstituted 3-pyrrolines is established from the phosphine-catalyzed [3+2] cycloaddition reaction of allenes with imines.     

Novel thiolated amino-alcohols as chiral ligands for copper-catalyzed asymmetric nitro-aldol reactions

Thiolated amino-alcohols have been synthesized and evaluated as a potential new class of chiral ligands for copper-catalyzed nitro-aldol reactions. The model nitro-aldol reaction took place smoothly at ambient temperature in the presence of catalytic amounts (5-15 mol %) of the ligands and copper(II) acetate to afford the nitro-aldol product in good to excellent yield without accompanying dehydration. Amino-alcohol ligands bearing N-(2-alkylthio)benzyl substituents provided only modest enantioselectivities (22-46% ee) while those carrying N-2-thienylmethyl substituents provided better enantioselectivities (up to 75% ee). A range of aromatic aldehydes were acceptable for the nitro-aldol reaction with nitromethane, giving moderate to good enantioselectivities (69-88% ee).