Metal-Free Chemoselective Oxidation of 4-Methylquinolines into Quinoline-4-Carbaldehydes

A convenient protocol for the synthesis of quinoline-4-carbaldehydes via chemoselective oxidation of 4-methylquinolines using hypervalent iodine(III) reagents as oxidant is described. This method highlights metal-free and mild reaction conditions, nice yield, good functional group tolerance, and high chemoselectivity.     

Synthesis of 2-amino-3-cyano 4-<Emphasis Type="Italic">H</Emphasis>-chromenes containing quinoline in water: computational study on substituent effects

An efficient, high yielding and environmentally benign strategy to the synthesis of new 2-amino-3-cyano-4-H-chromene derivatives, via one-pot three-component reaction involving malononitrile, various α- or β-naphthol and appropriate aromatic aldehydes including 2-chloroquinoline-3-carbaldehydes in the presence of morpholine in water, was achieved. During the development of the synthesis five new chromene derivatives were fruitfully synthesized. It was found that employing this approach, aromatic aldehydes bearing electron-withdrawing groups give higher yields of the corresponding products in shorter reaction times. This observation was in agreement with topological analysis of calculated electron density functions using density functional theory and quantum theory of atoms in molecules approaches.     

Pd/C-catalyzed alkynylation of β-chloroacroleins

The first Pd/C-mediated Sonogashira coupling of β-chloroacroleins with terminal alkynes is described here. Pd/C–CuI–PPh₃ was found to be an efficient catalyst system for this coupling reaction. Using this economic and general process a variety of 4-alkynyl-2H-chromene-3-carbaldehydes and 5-alkynyl-2,3-dihydro benzo[b]oxepine-4-carbaldehydes were prepared in good yields.     

4-Hydroxy-2-quinolones 123. Amidation of 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-<Emphasis Type="Italic">a</Emphasis>]-quinoline-4-carboxylic acid

The reaction of 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylic acid with thionyl chloride is accompanied by a transformation of the oxazoloquinolone ring to give 4-chloro-1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-3-carboxylic acid chloride. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1034–1042, July, 2007.     

Proline-catalyzed diastereoselective direct aldol reaction between 4-oxoazetidine-2-carbaldehydes and ketones

The reaction of enantiopure 4-oxoazetidine-2-carbaldehydes with unmodified ketones was catalyzed by L-proline as well as by D-proline, to give the corresponding gamma-amino-beta-hydroxy ketones with good yields and diastereoselectivities. The obtained results implied that (2R,3R)-4-oxoazetidine-2-carbaldehydes and L-proline are a matched pair for diastereoselective induction.     

Synthesis of Functionalized 1‐Benzamido‐1,4‐dihydropyridines via a One‐Pot Two‐Step Four‐Component Reaction

The one‐pot four‐component reaction of benzohydrazide, acetylenedicarboxylate, aromatic aldehydes and malononitrile in ethanol with triethylamine as base catalyst afforded functionalized 1‐benzamido‐1,4‐dihydropyridines in satisfactory yields. Under similar conditions, picolinohydrazide or nicotinohydrazide can also be successfully utilized in the reactions to give corresponding functionalized 1,4‐dihydropyridines. ¹H NMR data indicated that an equilibrium of cis/trans‐conformations exist in 1‐benzamido‐1,4‐dihydropyridines.     

Synthesis of bisarylmethyl-substituted pyrimidines and quinolines

The condensation of 2-chloro-8-methylquinoline-3-carbaldehyde, 2-chloroand 2-chloro-7,8,9,10-tetrahydrobenzo[h]quinoline-3-carbaldehydes, 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carbaldehyde, 6-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carbaldehyde, and 2-chloropyrido[1,2-a]pirimidine-3-carbaldehyde with N-substituted anilines gave the corresponding diaryl(hetaryl)methanes.     

Bismuth triflate catalyzed solvent-free synthesis of 2,4,6-triaryl pyridines and an unexpected selective acetalization of tetrazolo[1,5-a]-quinoline-4-carbaldehydes

Bismuth triflate has been found as a potential catalyst for an efficient and solvent-free synthesis of symmetrical 2,4,6-triarylpyridines in 86–93% yields. Moreover, catalytic reactivity of bismuth triflate toward tetrazolo[1,5-a]quinoline-4-carbaldehydes for the unexpected formation of their corresponding acetals has been exploited.     

Substituted Butanolides and Butenolides: XVII. Substituted 3-(Furan-2-ylmethylidene)furan-2(3<Emphasis Type="Italic">H</Emphasis>)-ones and 3-(Furan-2-ylmethylidene)dihydrofuran-2(3<Emphasis Type="Italic">H</Emphasis>)-ones

A number of furan-2-ylmethylidene-substituted lactones were synthesized by condensation of 5-alkylfuran-2(3H)-ones and 4-alkyldihydrofuran-2(3H)-ones with 5-substituted furan-2-carbaldehydes. The reactivity of furan-2(3H)-ones was higher than that of furan-2(5H)-ones due to formation of intermediate conjugated anion. The condensation of 4-alkyldihydrofuran-2(3H)-ones with furan-2-carbaldehydes required more severe conditions than the condensation with furan-2(3H)-ones. The substituent in the furan ring affects the reaction time and yield.     

Convenient synthesis of 1-aryl-9H-β-carboline-3-carbaldehydes and their transformation into dihydropyrimidinone derivatives by Biginelli reaction

In the present work, a practical synthesis of 1-aryl-β-carboline-3-carbaldehydes as versatile building blocks and their application in Biginelli reaction is reported. The starting material of the four-step synthesis is racemic tryptophan methyl ester. The procedure involves a Pictet–Spengler cyclization, a dehydrogenation, an ester reduction, and an alcohol oxidation step. The β-carboline-3-carbaldehydes were further transformed using a Biginelli reaction into derivatives containing a pharmacologically significant dihydropyrimidine ring at position-3.     

Reaction of 3-chloroquinoline-2,4-diones with ethanolamine and rearrangement of the reaction products

The reaction of tertiary α-chloroketones with ethanolamine has not been hitherto described in the literature. Herein, we describe the reaction of tertiary 3-chloroquinoline-2,4-diones with ethanolamine to give novel 3-(2-hydroxyethylamino)quinoline-2,4-diones. These compounds provide 3-(2-oxooxazolidin-3-yl)quinoline-2,4(1H,3H)-diones and new compounds with dimeric character after reaction with triphosgene. Molecular rearrangement proceeds during the reaction of 3-(2-hydroxyethylamino)quinoline-2,4-diones with isocyanic acid. Three types of reaction products arise: 2-(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-diones, 3-(2-hydroxyethyl)-3,3a-dihydro-2H-imidazo[4,5-]quinoline-4(5H)diones and primarily 5-hydroxy-1-(hydroxyethyl)-1′H-spiro[imidazolidine-5,3′-indole]-2,2′-diones. The reaction mechanism and product stereochemistry are discussed. The ¹H, ¹³C and ¹⁵N NMR spectra of the prepared compounds were measured, and all resonances were assigned from appropriate two-dimensional experiments.     

Convenient synthesis and unusual reactivity of 2-oxo-2H,5H-pyrano[3,2-c]chromenes

The reaction of 4-oxo-4H-chromen-3-carbaldehydes with coumarin-4-acetic acids under the Perkin conditions follows an interesting pathway that involves aldol reaction and subsequent intramolecular lactonization to afford 2-oxo-2H,5H-pyrano[3,2-c]chromene skeleton. In contrast to chromone-3-carbaldehydes, the same reaction with chromone-2-carbaldehydes yielded only the aldol condensation product. The reaction was performed under thermal and microwave conditions. The reactivity of 2-oxo-2H,5H-pyrano[3,2-c]chromenes in water, alcohol and acetic acid was described.     

4-Functionally Substituted 3-Heterylpyrazoles: VIII. 3-Aryl(heteryl)-4-hydroxyl(chloro)methylpyrazoles

3-Aryl(heteryl)pyrazole-4-carbaldehydes were reduced with sodium tetrahydridoborate under mild conditions to give 3-aryl(heteryl)-4-hydroxymethylpyrazoles which were converted into the corresponding 4-chloromethyl derivatives by treatment with thionyl chloride. The subsequent reaction with triphenylphos- phine led to formation of triphenyl(4-pyrazolylmethyl)phosphonium chlorides, and Wittig reaction of the latter with aromatic or heteroaromatic aldehydes yielded 4-[2-aryl(heteryl)ethenyl]pyrazoles.     

Synthesis of benzo[<Emphasis Type="Italic">g</Emphasis>]quinoline-5,10-diones

Addition of HCl to 2-amino-3-(4-methyl-3-oxopentynyl)-1,4-naphthoquinone in CHCl₃ at 20 °C is followed by its cyclization to 4-chloro-2-isopropylbenzo[g]quinoline-5,10-dione. Chlorine atom in this compound can be easily replaced by dialkylamino group upon treatment with secondary amines. 4-Dialkylamino-2-isopropylbenzo[g]quinoline-5,10-dione is also formed by the direct reaction of the starting ketone with secondary amines. Syntheses of 2-amino-3-(4-methyl-3-oxopentynyl)-1,4-naphthoquinone from 2-bromo-and 2-amino-3-iodo-1,4-naphthoquinones are also described. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2381–2385, December, 2007.     

Asymmetric synthesis of unusual fused tricyclic beta-lactam structures via aza-cycloadditions/ring closing metathesis

Conveniently substituted bis-beta-lactams, pyrrolidinyl-beta-lactams, and piperidinyl-beta-lactams undergo ring-closing methatesis using Grubbs' carbene, Cl(2)(Cy(3)P)(2)Ru=CHPh, to give medium-sized rings fused to bis-2-azetidinone, pyrrolidinyl-2-azetidinone, or piperidinyl-2-azetidinone systems. The diolefinic cyclization precursors can be obtained from optically pure 4-oxoazetidine-2-carbaldehydes bearing an extra alkene tether at position 1 or 3 of the beta-lactam ring via [2 + 2] cycloaddition of imino 2-azetidinones, N-metalated azometine ylide [3 + 2] cycloaddition, and subsequent N-acylation of the pyrrolidinyl nitrogen atom, or through aza-Diels-Alder cycloaddition of 2-azetidinone-tethered imines. Under standard reaction conditions, the combination of cycloaddition reactions of 2-azetidinone-tethered imines with ring-closing methatesis offers an asymmetric entry to a variety of unusual fused tricyclic 2-azetidinones bearing two bridgehead nitrogen atoms.     

Polyfunctional imidazoles: IV. Synthesis of 2-aryl-4-chloro-1-methyl(aryl)-1<Emphasis Type="Italic">H</Emphasis>-imidazole-5-carbaldehydes

2-Aroyl-2-[methyl(aryl)amino]acetamides reacted with the Vilsmeier-Haak reagent to give 2-aryl-4-chloro-1-methyl(aryl)-1H-imidazole-5-carbaldehydes.     

Derivation of fluorine-containing pyridine dicarboxylates IV. N-substituted dihydropyridine derivatives

The bio-activity observed for certain Hantzsch derived fluorine-containing dihydropyridinecarboxylates 6, 11 and 12 and pyridinecarboxylates 10 prompted the preparation of a number of related N-substituted dihydropyridines for the first time. One method involved a mixed Hantzsch sequence to give 2 from which unexpected side products 3–5 were also isolated and identified. A second preparative method relied on lithiobase deprotonation of 6, 11 and 12 followed by alkylation or acylation to give products 7–9 and 13–15 . Structure determination and stereo-assignments are discussed in terms of their spectral properties, and reaction mode.     

Synthesis of 2-substituted cinchoninic acid amides and their cyclization into 1,2,4-triazolo[4,3-α]-quinoline-9-and 1,2,4-triazino[4,3-a]quinoline-10-carboxylic acid amides

Substituted amides of 2-hydrazino- and 2-ethylhydrazinocinchoninic acids react with pyruvic acid and its ethyl ester to give amides of 3-methyl-4-oxo-1,2,4-triazino[4,3-a]quinoline-10-carboxylic acid. On reaction with aromatic aldehydes they are converted into amides of 2-ethyl-3-phenyl-2,3-dihydro-1,2,4-triazolo[4,3-a]quinoline-9-carboxylic acid, or, in the case of unsubstituted hydrazines, into amides of 2-arylidene-hydrazinocinchoninic acid, which was oxidized to substituted 1,2,4-triazolo[4,3-a]quinolines.Perm Pharmaceutical Academy, Perm 614600. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 701–705, May, 1977.     

Polyfunctional imidazoles: V. Synthesis of 1-aryl-4-chloro- 5-di(tri)fluoromethyl-1<Emphasis Type="Italic">H</Emphasis>-imidazoles

1-Aryl-4-chloro-1H-imidazole-5-carbaldehydes and 1-aryl-4-chloro-1H-imidazole-5-carboxylic acids reacted with sulfur(IV) fluoride to give, respectively, 1-aryl-4-chloro-5-difluoromethyl- and 1-aryl-4-chloro-5-trifluoromethyl-1H-imidazoles.