Plant coumarins: V. Palladium-catalyzed amination of 2-(1,3-dibromopropan-2-ylidene)oreoselone

Palladium-catalyzed amination of 2-(1,3-dibromopropan-2-ylidene)-7H-furo[3,2-g]chromene-3,7(2H)-dione with various amines and amino acid derivatives led to the formation of the corresponding 2-(1,3-diaminopropan-2-ylidene)-substituted oreoselones. The yields depended on the catalytic system, base, and amine structure. Di- and polyazamacrocyclic furocoumarin derivatives were obtained by reactions of 2-(1,3-dibromopropan-2-ylidene)-7H-furo[3,2-g]chromene-3,7(2H)-dione with linear di- and polyamines (hexamethylenediamine, spermine, spermidine, and 3,6-dithiaoctane-1,8-diamine), catalyzed by palladium complexes.     

Plant coumarins: VII. Amination of oreoselone trifluoromethanesulfonate

Amination of oreoselone trifluoromethanesulfonate with N-substituted piperazines, anabasine, aniline derivatives, quinolin- and isoquinolinamines, and amino acids of the penicillin and cephalosporin series in the presence of palladium complexes gave the corresponding N-substituted 3-aminofurocoumarins. The yield of the amination products depended on the catalytic system and base used.     

Plant coumarins: VI. Synthesis of 3-vinylfurocoumarin derivatives based on oreoselone

Palladium-catalyzed Heck reaction of oreoselone trifluoromethanesulfonate with various terminal alkenes (methyl acrylate, styrene, vinylpyridines, N-vinylpyrrole, and N-vinyl-1,2,4-triazole) led to the formation of the corresponding (E)-3-vinyl-7H-furo[3,2-g]chromen-7-ones. The yield was found to depend on the catalytic system and initial olefin structure.     

Synthesis and reactions of 4-(arylhydrazino)coumarins

The interaction of 4-hydroxycoumarin with phenyl-, 2-chlorophenyl- and 4-bromophenyhydrazine hydrochlorides in the presence of triethylamine led in all cases to the corresponding 4-(arylhydrazino)-coumarins and 1-aryl-3-(2-hydroxyphenyl)-2H-pyrazolin-5-ones. 4-(Arylhydrazino)coumarins reacted with 4-chlorobenzaldehyde in the presence of piperidine acetate to give the corresponding 2-aryl-3-(4-chlorophenyl)[1]benzopyrano[4,3-b]pyrazol-4-ones. The reaction of 4-(4-bromophenylhydrazino)-coumarin with 4-chlorobenzaldehyde in the presence of piperidine acetate and an excess of piperidine gave 2-(4-bromophenyl)-5-(4-chlorophenyl)-3-(2-hydroxyphenyl)-4-(piperidinocarbonyl)pyrazole, but the reaction of phenyl- and 4-(2-chlorophenylhydrazino)coumarins with 4-chlorobenzaldehyde gave 1-aryl-5-(4-chlorophenyl)-3-(2-hydroxyphenyl)-4-(1-piperidino)carbonyl-4,5-dihydropyrazoles.     

3-(2-Pyridyl)coumarins

3-(2-Pyridyl)coumarins were prepared by reaction of substituted salicylaldehydes and 2-pyridylacetonitrile. Benzylation, acylation, and aminomethylation of 7-hydroxy-3-(2-pyridyl)coumarin was studied. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 428–431, September–October, 2005.     

3-(2-Quinolyl)- and 3-(5-carbethoxyfuryl-2)coumarins

3-(2-Quinolyl)- and 3-(5-carbethoxyfuryl-2)coumarins were prepared by reaction of substituted salicylaldehydes and hetarylacetonitriles. Alkylation and acylation of 3-hetaryl-7-hydroxycoumarins were studied. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 432–434, September–October, 2005.     

Chemistry of 3-hetarylcoumarins. 2. 3-(2-thiazolyl)coumarins

3-(2-Thiazolyl)coumarins were obtained by the reaction of substituted salicylaldehydes with 2-thiazolylacetonitriles. Methylation, acylation, and aminomethylation were studied for the 7-hydroxy-substituted products.For Communication 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1632–1644, November, 2004.     

Synthesis of 4-(2-hydroxymethylaryl)coumarins

New 4-(2-hydroxymethylaryl)coumarins were prepared using the Suzuki—Miyaura cross-coupling at the key step. According to X-ray diffraction data, the compounds obtained are structural analogs of the natural stilbene combretastatin A-4, which exhibits potent antitumor activity.     

Chemistry of 3-Hetarylcoumarins. 1. 3-(2-Benzazolyl)coumarins

The reaction of substituted salicylaldehydes with 2-benzimidazolyl- and 2-benzothiazolylacetonitriles gives the corresponding 3-hetarylcoumarins. The alkylation, acylation, and aminomethylation reactions of these 7-hydroxy-substituted hetero isoflavonoid analogs has been studied.     

One-pot synthesis of 2-(2-hydroxyaryl)quinolines: reductive coupling reactions of 2′-hydroxy-2-nitrochalcones

A one-pot synthesis of novel 2-(2-hydroxyaryl)quinolines have been developed from the intramolecular reductive coupling reactions of 2′-hydroxy-2-nitrochalcones, induced by stannous chloride in acidic medium (HCl/AcOH). In some cases these transformations can be performed with ammonium formate/Pd-C in methanol.     

Fused-s-triazino heterocycles. XI. Displacement reactions of 7,9-dichloro-2,5-bis(trichloromethyl)-1,3,4,6,9b-pentaazaphenalene

The preparation of 7,9-dichloro-2,5-bis(trichloromethyl)-1,3,4,6,9b-pentaazaphenalene ( 1e ) by the chlorination of 2-trichloromethyl-5-methyl-1,3,4,6,9b-pentaazaphenalene ( 1a ) using molecular chlorine is described. Displacement of one or both trichloromethyl groups of 1e by a variety of nucleophiles led to the corresponding 7,9-dichloro-2,5-bis-substituted or 7,9-dichloro mixed 2,5-disubstituted derivatives. The reaction of 1a with N-chlorosuccinimide proved not to be a useful route to 1e but instead led primarily to substitution of positions 7 and/or 9 by chlorine.     

Synthesis of N-(tosyl)azetidin-2-imines

A synthetic route for N-(tosyl)azetidin-2-imines $\text{6}$, a novel class of derivatives of β-lactams, has been developed. The procedure is applicable to the synthesis of azetidin-2-imines related to penicillins and cephalosporins.     

Cross coupling reactions of organozinc iodides with solid-supported electrophiles: synthesis of 4-substituted benzoic and 3-substituted (E)- and (Z)-propenoic acids and amides

The solid-supported iodobenzoic acid derivatives 8-10 were coupled with a range of organozinc reagents 1-4 under palladium(o) catalysis. The coupled products released by acidic cleavage with TFA were obtained in high purities after recrystallisation. Analogous coupling of solid-supported (E)- and (Z)-3-iodoacrylic acids 18a, 18b, 19 and 20 gave (E)- and (Z)-alpha,beta-unsaturated acids and amides 21-27 stereospecifically.     

Syntheses of 4-(1-alkynyl)-2(5H)-furanones and coumarins via the palladium catalyzed cross-coupling reactions of potassium alkynyltrifluoroborates

An efficient synthesis of 4-(1-alkynyl)-2(5H)-furanones has been developed utilizing a palladium catalyzed coupling reaction of β-tetronic acid bromide with potassium alkynyltrifluoroborates in the absence of base. 4-Alkynylcoumarins were also synthesized using this method. The reactions are straightforward and the yields are excellent.     

Oligomer-oligomer versus oligomer-monomer C(2)-C(2)' coupling reactions in polypyrrole growth.

The C(2)-C(2)' coupling reactions of oligopyrrole radical-cations of increasing length generated by electrochemical oxidation have been modeled by transition state calculations. The modeling approach takes into account solvent effects and (i) shows that the coupling distance in the transition state decreases with oligomer length, (ii) demonstrates that dimerization rates in the gas phase decrease with oligomer length but increase in water, (iii) suggests that in a less solvating medium the dimerization rates could be equivalent, (iv) indicates that in all solvents quaterpyrrole and sexipyrrole formation is faster through a coupling reaction between oligomer and monomer radical-cations than two oligomer radical-cations, and (v) suggests that for the formation of a long oligopyrrole from oligopyrrole-pyrrole reactions the mechanism might involve the coupling of the oligopyrrole dication with a non-oxidized pyrrole unit instead of the coupling of two radical-cations or that of the oligopyrrole dication with a pyrrole radical-cation.     

Catalyst- and solvent-free coupling of 2-methyl quinazolinones and 3-(trifluoroacetyl)coumarins: An environmentally benign access of quinazolinone derivatives

An environmentally benign highly atom-economic protocol for the construction of the CC bond has been developed under catalyst- and solvent-free conditions. This protocol involves the efficient coupling of 2-methyl quinazolinones with 3-(trifluoroacetyl)coumarins for the access of quinazolinone derivatives in excellent yields (up to 90 %). The crystal structure of compound 3di was investigated by X-ray diffraction analysis. The biological activities, such as in vitro antifungal activity of the quinazolinone derivatives against Fusarium graminearum, Fusarium moniliforme, Fusarium oxysporum, Phytophthora parasitica var nicotianae, and Rhizoctonia solani Kuhn, were investigated. The bioassay results indicated that most of the target products exhibited promising fungicidal activities, and compound 3 cl exhibited 95 % fungicidal activity against R. solani, with an EC₅₀ value of 10.6 μg/mL.     

An Efficient One-Pot Synthesis of 3-(2-Benzothiazolyl)coumarins

Some 3-(2-benzothiazolyl)coumarin imines and 3-(2-benzothiazolyl)coumarins are prepared from 2-benzothiazolylacetonitrile and 2-hydroxybenzaldehydes in ethanol in the presence of catalytic amount of NaOH.     

VO(acac)(2)-catalyzed oxidative coupling reactions of phosphonium salts.

A novel eco-safer protocol for the preparation of symmetric or asymmetric olefins directly from phosphonium salts under oxygen atmosphere in the presence of VO(acac)(2) (1.0 mol%) was developed.     

Oxygen ylides - II. : Photochemical and rhodium-catalyzed reactions of diazomethane with (S)-2-methyloxetane

Photolysis of diazomethane in (S)-2-methyloxetane gives 2- and 3-methyltetrahydrofuran (1:3.2), the latter being formed with 21 % net retention of configuration. In contrast, rhodium acetate catalysis yields racemic 3-methyltetrahydrofuran exclusively.     

Reagents for new heteroannelation reactions III. 2-(Methylthio)-2-thiazoline

Summary A variety of partly novel tri- and tetracyclic hetero systems were obtained by reaction of heteroaromatic 2-aminoesters with 2-(methylthio)-2-thiazoline, yielding double-annelation of a thiazolo[2,3-b]pyrimido moiety in a one-pot process.On leave from University of Chittagong, Bangladesh