Application of directed metalation in synthesis. Part 8: Interesting example of chemoselectivity in the synthesis of thioaurones and hydroxy ketones and a novel anionic ortho-Fries rearrangement used as a tool in the synthesis of thienopyranones and thiafluorenones

Chemoselective synthesis of thioaurones or 3-hydroxy benzo[b]thiophen-2-aryl ketones, 1-hydroxy naphtho[2,1-b]thiophen-2-aryl ketones and chalcones from N,N-diethyl-ortho-methyl sulfanyl aryl amides were described. (Benzo[b]thiophen-2-yl) alkylates and (naphtho[2,1-b]thiophen-2-yl) alkylates undergo a novel anionic ortho-Fries rearrangement leading to (3-hydroxy benzo[b]thiophen-2-yl) and (1-hydroxy naphtho[2,1-b]thiophen-2-yl) alkyl ketones. The hydroxy ketones were used as intermediates in the synthesis of wide range of benzothienopyranones and thiafluorenones.     

Two-pot synthesis of N,N-disubstituted 4H-3,1-benzothiazin-2-amines from aryl(2-isothiocyanatophenyl)methanones and secondary amines

A convenient synthesis of N,N-disubstituted 4H-3,1-benzothiazin-2-amines from aryl(2-isothiocyanatophenyl)methanones using a two-pot procedure has been developed. Thus, treatment of these isothiocyanato ketones with secondary amines gave the corresponding keto thioureas, which were allowed to react with sodium borohydride or methylmagnesium bromide to afford 1,1-dialkyl-3-{2-[aryl(hydroxy)methyl]phenyl}thioureas or 1,1-dialkyl-3-[2-(1-aryl-1-hydroxyethyl)phenyl]thioureas, respectively, in one pot. Hydrobromic acid-mediated cyclization of these hydroxy thiourea precursors provided the desired 4H-3,1-benzothiazin-2-amines.     

4-Functionally Substituted 3-Heterylpyrazoles: IV. 1-Phenyl-3-aryl(heteryl)-5-(4-pyrazolyl)-2-pyrazolines

3-Aryl(heteryl)-4-formylpyrazoles in condensation with methyl aryl(heteryl) ketones afforded 1-aryl(heteryl)-3-[3-aryl(heteryl)-4-pyrazolyl]propenones. The latter reacted with phenylhydrazine yielding 1-phenyl-3-aryl(heteryl)-5-(4-pyrazolyl)-2-pyrazolines.     

Reaction of 2-Aryl-5-R-5,6-dihydro-7H-[1,2,4]-triazolo[5,1-<Emphasis Type="Italic">b</Emphasis>][1,3]thiazin-7-ones with Aryl Bromomethyl Ketones and Benzyl Bromide

The products of the reaction of 2-aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones with aryl bromomethyl ketones are 2-aryl-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones and aryl methyl ketones or 2,5-diaryl[1,3]thiazolo[3,2-b][1,2,4]triazoles and 3-phenyl-2-propenoic acid, depending on the structure of R. The reaction of 2-aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones with benzyl bromide yields 5-aryl-3-benzylthio-4H-1,2,4-triazoles and 3-aryl-2-propenoyl bromide. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 905–909, June, 2005.     

Synthesis and tautomerism of 2-[3(5)-aryl(methyl)pyrazol-4-yl]-1-benzimidazoles

An efficient method has been developed for the synthesis of 2-[3(5)-aryl(methyl)pyrazol-4-yl]-1H-benzimidazoles by cyclocondensation of 2-acylmethyl-1H-benzimidazoles benzoylhydrazones with DMF dimethylacetal. The tautomerism of the compounds obtained via migrations of a proton between the pyrazole nitrogen atoms has been studied by ¹H NMR. The more stable tautomers have electron acceptor aryl substituents placed at position 3 of the pyrazole ring and electron donor aryl substituents or a methyl at position 5. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1370–1377, September, 2006.     

Synthesis of methyl 7-aryl(hetaryl, cyclohexenyl)-10-(1,3-benzodioxol-5-yl)-8-oxo-7,8,9,10,11,12-hexahydro-benzo[b][1,7]phenanthroline-9-carboxylates

Three-component condensation of quinolin-5-amine with methyl 2-(1,3-benzodioxol-5-yl)-4,6-dioxocyclohexane-1-carboxylates and aromatic aldehydes (or cyclohex-3-ene-1-carbaldehyde) afforded new hexahydrobenzo[b][1,7]phenanthroline derivatives. The condensation in butan-1-ol is strictly regioselective but not stereoselective, so that mixtures of cis- and trans-isomeric methyl 7-aryl(hetaryl, cyclohexenyl)-10-(1,3-benzodioxol-5-yl)-8-oxo-7,8,9,10,11,12-hexahydrobenzo[b][1,7]phenanthroline-9-carboxylates at a ratio of ～40: 60% are formed.     

Reaction of methyl 1-bromocyclopentane- and -cyclohexanecarboxylates with zinc and 2-arylmethylideneindan-1,3-diones

Methyl 1-bromocyclopentanecarboxylate and methyl 1-bromocyclohexanecarboxylate reacted with zinc and 2-arylmethylideneindan-1,3-diones to give methyl-1-[(aryl)(1,3-dioxo-2,3-dihydro-1H-inden-2-yl)-methyl]cyclopentane(or cyclohexane)carboxylates and 4′-aryl-2′H-spiro[cyclopentane(or cyclohexane)-1,3′-indeno[ 1,2-b]pyran]-2′,5′(4′H)-diones.     

Anodic formation of 3,6-diaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles and 2(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles together with the unknown systems 2-(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles were obtained by anodic oxidation, under aprotic conditions, of aryl aldehyde N-(5-aryl-1,3,4-thiadiazol-2-yl) hydrazones. Mechanistic proposals are given.     

Transformation of 4-aryl(heteryl)-2,6-diamino-3,5-dicyano-4H-thiopyrans into substituted acrylonitriles, 1,4-dihydropyridines, 2,3,4,7-tetrahydrothiazolo[3,2-a]pyridine, and 4,7-dihydrothieno[2,3-b]pyridine

Cross-recyclization of 4-aryl(heteryl)-2,6-diamino-3,5-dicyano-4H-thiopyrans with α-bromoketones or alkyl halides formed substituted 3-aryl-2-(4-R-thiazol-2-yl)acrylonitriles, 2-alkylsulfanyl-1,4-dihydropyridines, 2,3,4,7-tetrahydrothiazolo[3,2-a]pyridine, and 4,7-dihydrothieno[2,3-b]pyridine.     

Synthesis of some 3-aryl-4-oxothiazolin-2-yl-[3-(2-aryl)indolyl]hydrazories

Several 4-aryl-l-[3-(2-aryl)indolyl]-3-thiosemiearbazones and 3-aryl-4-oxothiazolin-2-yl-[3-(2-aryl)indolyl] hydrazones were synthesized as possible antilertility agents. J. Heterocyclic Chem., 15 , 677 (1978)     

A new synthesis of benzo[b]thiophenes utilizing an interrupted Pummerer reaction

A convenient synthesis of 3-arylbenzo[b]thiophenes utilizing an interrupted Pummerer reaction of 2-(1-arylvinyl)phenyl ethyl sulfoxides is described. Thus, treatment of these sulfoxides, which were readily prepared from 2-sulfanylphenyl ketones or 2-fluoro-5-methoxybenzaldehyde, with acetic anhydride at 100 °C afforded 3-arylbenzo[b]thiophenes in reasonable yields.     

Haloacetylated enol ethers. 13. Synthesis of N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-1-buten-1-yl]-o-phenylenediamines and 2-trichloromethyl-4-aryl-3H-1,5-benzodiazepines

The synthesis and isolation of the intermediates N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-1-buten-1-yl]-o-phenylenediamines 2a-f and the corresponding 2-trichloromethyl-4-aryl-3H-1,5-benzodiazepines 3c-g or benzimidazoles 4a-b derivatives obtained from the intramolecular cyclization of 2a-f or from direct cyclo-condensation reaction of β-alkoxyvinyl trichloromethyl ketones 1a-g with o-phenylenediamine, is reported. Depending of the structure of the β-alkoxyvinyl trichloromethyl ketones or the N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-buten-1-yl]-o-phenylenediamines and the reactions conditions, benzimidazoles or 3H-1,5-benzodiazepines were obtained.     

Diastereoselective approach to 11-aryl steroid skeletons through a cobalt(I)-mediated [2+2+2] cyclization of allenediynes

The cobalt(I)-mediated [2+2+2] cycloaddition reactions of allenediynes of yne-allene-yne type bearing an aryl group on the allene are described. The cyclizations are totally chemo- and regioselective and show low diastereoselectivities. η⁴-Complexed tricyclic (6,6,6) compounds were obtained in good yields as mixtures of endo/exo diastereomers. The cyclization is also compatible with an oxyfunctionality at C3. By designing an allenediyne having a preexisting D ring, we succeeded in building skeletons of 11-aryl steroids in one step and in a totally diastereoselective manner and with simultaneous introduction of an angular methyl group at C10 and an aryl substituent at C11.     

Synthesis of N-arylsulfonyl-2-aryl(hetaryl)aminoacetic acids

Hydrolytic transformations of 4-[2,2,2-trichloro-1-(arylsulfonylamino)-and-(ethoxycarbonylamino)ethyl]phenyloxy(or sulfanyl)acetic acids under microwave irradiation in alkaline medium involve both trichloromethyl group and ester fragment to give N-arylsulfonyl-2-[4-carboxymethyloxy(or sulfanyl)phenyl]-2-aminoacetic acids in good yields. Hydrolysis of methyl 4-[2,2,2-trichloro-1-(arylsulfonylamino)ethyl]phenyloxy(or sulfanyl)acetates without microwave activation occurs only at the ester group with quantitative formation of 4-[2,2,2-trichloro-1-(arylsulfonylamino)ethyl]phenyloxy(or sulfanyl) acetic acids. N-[2,2,2-Trichloro-1-(1-naphthyl, 2-furyl, and 1-methylindol-3-yl)ethyl]-4-chlorobenzenesulfonamides in alkaline medium under microwave irradiation were converted in 10–15 min into the corresponding N-(4-chlorophenylsulfonyl)-2-aryl-2-aminoacetic acids in preparative yields.     

Ultrasound- and microwave-assisted synthesis of (E)-1-aryl-3-[2-(piperidin-1-yl)quinolin-3-yl]prop-2-en-1-ones and (E)-1-aryl-3-[2-(pyrrolidin-1-yl)quinolin-3-yl]prop-2-en-1-ones,and their antimicrobial activity

Series of new (E)-1-aryl-3-[2-(piperidin-1-yl)quinolin-3-yl]prop-2-en-1-ones and (E)-1-aryl-3-[2-(pyrrolidin-1-yl)quinolin-3-yl]prop-2-en-1-ones have been efficiently prepared via the Claisen-Schmidt condensation of 2-(piperidin-1-yl)quinoline-3-carbaldehyde and 2-(pyrrolidin-1-yl)quinoline-3-carbaldehyde, respectively, with aryl methyl ketones under conditions of ultrasound and microwave irradiation. Structures of the products have been confirmed by IR, ¹H NMR, ¹³C NMR, and mass spectroscopy, as well as by elemental analysis. Evaluation of the in vitro antibacterial activity against bacterial (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) and fungal (Aspergillus niger and Candida metapsilosis) strains has revealed good antimicrobial activity of some of the tested compounds.     

Synthesis of methyl 3-amino-4-aryl(or methyl)sulfonyl-2-thiophenecarboxylates from 3-alkoxy-2-aryl(or methyl)-sulfonylacrylonitriles

The synthesis of a series of methyl 3-amino-4-aryl(or methyl)sulfonylthiophene-2-carboxylates by reaction of 3-alkoxy-2-aryI(or methyl)sulfonylacrylonitriles with methyl thioglycolate in the presence of triethylamine is described. Hydrolysis/decarboxylation of the ester at the 2-position and acylation of the resulting amine represents a convenient route to 4-arylsulfonyl-3-carboxamidothiophenes. Attempted acylation of a title aminothiophene under standard conditions was unsuccessful.     

A novel synthesis of aryl tethered imidazo[4,5-b]pyrazin-2-ones through in situ ring construction and contraction

An innovative synthesis of aryl tethered 1,3-dimethylimidazo[4,5-b]pyrazin-2-ones 4 and 6 has been delineated through base catalyzed ring transformation of 6-aryl-4-(piperidin-1-yl)-2H-pyran-2-one-3-carbonitriles 1 and methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates 5 with 7-acetyl-1,3-dimethyllumazine 2 with subsequent ring contraction of the fused pyrimidine to an imidazole ring. An additional product, methyl [6-(1,3-dimethyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyrazin-5-yl)-4-thiophen-2-ylpyran-2-ylidene]acetate 8b, was also isolated from the reaction of 5 and 2, as a minor constituent.     

Substituent directed regioselective synthesis of 2-oxonicotonic acids and methyl nicotinates

An innovative synthesis of aryl tethered 1,2-dihydro-2-oxopyridine-3-carboxylic acids has been developed through nucleophile induced ring transformation of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates using either cyanamide or arylamidine in excellent yields. Further, the reaction of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates with formamidine acetate under analogous reaction conditions did not follow the same course of reaction and produced methyl nicotinate, regioselectively, in good yield. Decarboxylation of a 6-aryl-4-methylsulfanyl-1,2-dihydro-2-oxopyridine-3-carboxylic acid has been achieved by heating in PPA. The 4-methylsulfanyl substituent in 3 has also been oxidized to the corresponding methylsulfonyl group with m-chloroperbenzoic acid.     

Cyclocondensation reaction of 4-aryl-4-methoxy-1,1,1-trifluoro-3-buten-2-ones with urea: Synthesis of novel 6-aryl(5-methyl)-4-trifluoromethyl-2(1H)-pyrimidinones

The synthesis of a novel series of eleven 6-aryl(5-methyl)-4-trifluoromethyl-2(1H)-pyrimidinones, where aryl=Ph, 4-CH₃Ph, 4-FPh, 4-ClPh, 4-BrPh, 4-OCH₃Ph and alkyl=H, CH₃, from the reaction of 4-aryl-4-methoxy-1,1,1-trifluoro-3-buten-2-ones with urea in the presence of hydrochloric acid, is reported. Trifluoroacetylation of acetophenone- and propiophenone-dimethylacetals derived from phenones, was employed to obtain the precursors.     

An efficient phosphine-free palladium coupling for the synthesis of new 2-arylbenzo[b]thiophenes

Straightforward and rapid access to 2-arylbenzo[b]thiophenes has been developed. It involved a catalytic coupling of 3-activated benzo[b]thiophenes with several aryl halides in the presence of a phosphine-free palladium system. In case of fragile functional groups such as aldehydes, a quaternary ammonium was used as an additive as with the other substrates, the coupling performed better and faster in the presence of a crown ether, the best one being DCH-18-C-6, with good yields and low reaction times. This method would provide a direct access to novel structures of biological interest.