Gallium(III) halide promoted synthesis of 1,3,5-triaryl- 1,5-dihalo-1,4-pentadienes

Aryl substituted alkynes undergo smooth coupling with aldehydes in the presence of gallium(III) halides under extremely mild conditions to afford the corresponding 1,3,5-triaryl-1,5-dihalo-1,4-pentadienes in good yields with E,Z-selectivity. Similarly 1,3,5-triaryl-1,5-dichloro-1,4-pentadienes are also obtained with niobium(V) chloride.     

Boron trihalide mediated alkyne-aldehyde coupling reactions: a mechanistic investigation

A boron trihalide mediated alkyne-aldehyde coupling reaction leading to stereodefined 1,3,5-triaryl-1,5-dihalo-1,4-pentadienes is described. The study led to the discovery of a direct substitution of hydroxyl groups by stereodefined alkenyl moieties using alkenylboron dihalides. During the investigation, it was also discovered that, at low temperatures, the reaction of BCl3 with alkynes produces monovinylboron dichloride rather than the reported divinylboron chloride. A modified reaction mechanism for the boron trichloride mediated alkyne-aldehyde coupling reaction is now proposed. The reaction temperature and mode of addition have been found to have dramatic affects on the stereochemistry of the diene products.     

A novel carbon-carbon bond formation by the Lewis acid catalyzed reaction of β-styrylsilane with acetal

Treatment of (E)- and (Z)-β-styryltrimethylsilanes with benzaldehyde diethyl acetal in the presence of Lewis acid affords selectively 1,3,5-tri-phenyl-(E,E)- and (E,Z)-1,4-pentadienes, respectively.     

Reaction of 4-oxoalkane-1,1,2,2-tetracarbonitriles with 1,3,5-trlaryl-2,4-diaza-1,4-pentadienes

2-Aryl-1,2,3,4-tetrahydropyridine-3,3,4,4,-tetracarbonitriles and 1,3,5-triaryl-9-oxo-1,2,3,4b,5,6,8a,9-octahydropyrido[3,4:3,4]pyrrolo[1,2-a][1,3,5]triazine-4b,8a-dicarbonitriles are formed by the reaction of 4-oxoalkane-1,1,2,2-tetracarnonitriles with 1,3,5-triaryl-2,4-diaza-1,4-pentadienes depending on the solvent used.Chuvash State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1395–1409, October, 1996. Original article submitted October 2, 1996.     

Unexpected synthesis of 1,3,5-triarly-1,5-diketones from aryl ketones via di-enamine mechanism

An unexpected reaction of aryl ketone with acetohydrazone of aromatic aldehyde via 1,2-di-enamine/di-iminium mechanism was discovered, leading to efficient synthesis of 1,3,5-triaryl-1,5-diketones in good to excellent yields.     

Niederkoordinierte Phosphorverbindungen. 59. 2,4,6-Tri-tert-butylphenylphosphaketen,ein Baustein gemischt substituierter Phospha-carba-polyene

Low-Coordinated Phosphorus Compounds. 59. 2,4,6-Tri-(butyl)phenylphosphaketene, a Synthon for Substituted Phospha-Carba-Polyenes Reaction of 2,4,6-tri(tbutyl)phenylphosphaketene 1 with dislylphosphanes in the ratio 2:1 yields 1,3,5-triphospha-1,4-pentadienes. P-silylated 1,3-diphosphapropenes are intermediates in this reaction, which add on diphenylketene forming 1,3-diphospha-1,4-pentadienes. 1,3,5-triphospha-1,4-pentadiene 10 is formed by reaction of 1 with tris(trimethylsilyl)phosphane, the silyl-function of which can be replaced by H, Li, or Cl. The structures of the new phospha-carbadienes are confirmed by the clear synthesis, ³¹P-n.m.r.-spectroscopy, and partially by X-ray.     

Regioselective synthesis of cis- and trans-2,4,5-triarylimidazolines and 2,4,5-triarylimidazoles from available reagents

Novel data were obtained concerning the reaction of aromatic aldehydes with ammonia. A preparative method for the synthesis of new substituted 1,3,5-triaryl-2,4-diazapenta-1,4-dienes was developed. These products are the starting reactants for syntheses of cis- and trans-2,4,5-triaryl-2-imidazolines and 2,4,5-triarylimidazoles.     

The Baylis-Hillman reaction: one-pot facile synthesis of 2,4-functionalized 1,4-pentadienes

The Baylis-Hillman coupling between activated alkenes and alkyl 2-(bromomethyl)prop-2-enoates in the presence of DABCO (or DBU) leading to the formation of 2,4-functionalized 1,4-pentadienes, has been described.     

Synthesis and properties of z-1,3-bis-(aryl)-4-bromo-2-buten-1-ones

Bromination of 1,3-bis(aryl)-2-buten-1-ones by N-bromosuccinimide in anhydrous carbon tetrachloride gives Z-1,3-bis(aryl)-4-bromo-2-buten-1-ones. The effect of the nature of substituent in the benzene ring on the course of a reaction with nucleophiles has been studied. Heating an alcohol solution of these ketones (Ar = 4-MeOC₆H₄, 4-ClC₆H₄) in the presence of acid or in the presence of base (Ar = Ph) gave 2,4-bis(aryl)furans. Treatment of 1,3-bis(aryl)-4-bromo-2-buten-1-ones with thioacetamide gave 2,4-bis(aryl)thiophenes. The oxidation of the halo-substituted dypnones with H₂O₂/NaOH gave (3-bromomethyl-3-aryl-2-oxiranyl)(aryl)methanones. The reaction of halo-substituted dypnones with aryl hydrazines gave 1,3,5-triaryl-1,6-dihydropyridazines or 1,3,5-triarylpyridazinium bromides depending on the structure of the reagents.     

2,4-diazapenta-1,4-dienes in the synthesis of 2,6-diaryl-3,5-dinitropiperidines

2,4,6-Triphenyl-and 2,6-diaryl-3,5-dinitropiperidines were synthesized in 70–79% yields by reaction of 1,3,5-triaryl-2,4-diazapenta-1,4-dienes with 2,2-dimethyl-and 2-phenyl-1,3-dinitropropanes.     

Organoboron compounds: CDXII. The synthesis of 2-substituted 1-iodo-1,4-pentadienes by iodination of 1,4-pentadienylboron derivatives

2-Substituted dimethoxy(1,4-pentadienyl)boranes, which are obtained by the condensation of triallylborane with acetylenic compounds followed by methanolysis, react with iodine in the presence of NaOH to form 2-substituted 1-iodo-1,4-pentadienes.     

Palladium(0) nanoparticle catalyzed cross-coupling of allyl acetates and aryl and vinyl siloxanes

The cross-coupling of allyl acetates and aryl and vinyl siloxanes proceeds readily by the catalysis of in situ generated palladium(0) nanoparticles. The reactions are stereoselective, and (E)-coupling products are obtained both from cis and trans allyl acetates. The coupling with vinyl siloxanes provides a novel protocol for the synthesis of 1,4-pentadienes.     

Preparation of 2-(Tetrahydrofuran-2′-YL)-l,4-Pentadienes From γ-Allenyl Alcohols via Oxymercuration Followed by Palladium(II)-Medlated all Ylation

Intramolecular oxymercurations of γ-hydroxy- or γ-silyloxyallenes yielded α-(tetrahydrofuran-2-yl)vinylmercury intermediates which underwent coupling with allylic halides in the presence of palladium(II) chloride. The yields of the resulting 2-(tetrahydrofuran-2′-yl)-1,4-pentadienes diminished when either the vinylmercury compound or the allylic halide was substituted.     

Niederkoordinierte Phosphorverbindungen. 60 [1]. Reaktionen von Iminomethylidenphosphanen mit Trimethylsilylphosphanen

Low-Coordinated Phosphorus Compounds. 60. Reactions of Iminomethylidenphosphanes with Trimethylsilylphosphanes The preparation of the new, monomer stable N-n-propyl-P-(2,4,6-tri-tertbutylphenyl)iminomethylidenphosphane 1 c is presented. The reactions of this compound and those of the already known iminomethylidenphosphanes 1a, b with trimethylsilylphosphanes are described. In non-polar solvents, 1,3-diphosphapropenes 4a—h respectively 1,3,4-triphospha-1-butenes 6a—d are obtained. In polar solvents, the reaction of 1b, c with phenyl-bis(trimethylsilyl) phosphane 3d results in the formation of 1,3,5-triphospha-1,4-pentadienes 7a, b and 8a, b through double addition. While tempering the new phosphacumulene 1c in solution, dimerisation occurs and yields the 1,3-diphosphetane 2c . The reaction of the 1,2-bis(trimethylsilyl)diphosphane 5b with 1c in acetonitrile produces the new 1,3,4,6-tetraphospha-1,5-hexadiene 9 . In contrast to analogous compounds with sterically less pretentious substituents at the double-bonded phosphorous, 9 shows no Cope-rearrangement.     

1,3,5-Triaryl-1,3,5-Triazinane-2,4,6-Trithiones: Synthesis,Electronic Structure and Linear Optical Properties

The synthesis of four new 1,3,5-triaryl-1,3,5-triazinane-2,4,6-trithione derivatives (thioisocyanurates) and two new partially thionated analogues from the corresponding 1,3,5-triaryl-1,3,5-triazinane-2,4,6-triones (isocyanurates) is reported, together with their spectroscopic properties. DFT calculations and comparison with the corresponding isocyanurates evidence the impact of the oxygen-for-sulfur replacement on the electronic structure and linear optical properties of these heterocycles. A bathochromic shift of the absorption bands and more efficient quenching of the fluorescence was observed.     

A new halopropargylation of alkynes promoted by boron trihalides. highly stereo- and regioselective syntheses of substituted (Z)-1-halo-1,4-enyne derivatives

[reaction: see text] A new halopropargylation of alkynes promoted by boron trihalides has been developed. Reactions of (Z)-2-halo-1-vinylboron dihalides (generated in situ via reaction of alkynes with boron trihalides) with lithium propargyloxides in CH(2)Cl(2) at room temperature produce the corresponding (Z)-1-halo-1,4-enynes in modest to good yields.     

A novel titanium tetrahalide-mediated carbon-carbon bond-forming reaction: regioselective synthesis of substituted (E,Z)-1,5-dihalo-1,4-dienes

Reactions of aldehydes with 2 equiv of alkyne in the presence of TiX(4) (X = Cl, Br) regioselectively generated 1,5-dihalo-1,4-dienes in moderate to good yields with high (E,Z)-stereoselectivity. [reaction: see text]     

Reactions of 1,4-Dianion of Methyl 2-Thienyl Ketone N-Ethoxycarbonylhydrazone with Derivatives of Carboxylic Acids,and the Synthesis of Pyrazolotriazin-7-ones

1,3,5-trisubstituted pyrazoles were obtained by reaction of carboxylic acids derivatives with 1,4-dianion of methyl 2-thienyl ketone N-ethoxycarbonylhydrazone. The dianion was prepared by treating the hydrazone with butyllithium in THF at -78°C. Besides were prepared 4-methyl (or 4-phenyl)-2-(2-thienyl)-6H-pyrazolo[1,5-d][1,2,4]triazin-7-ones from the corresponding 1,3,5-trisubstituted pyrazoles synthesized respectively with the use of ethyl pyruvate and ethyl phenylglyoxylate.     

Role of tautomerism and rotational isomerism in the interaction of α-hydroxyanthraquinones with boric acid

The products of reaction of α-hydroxyanthraquinones with boric acid are mixtures of 9,10-, 1,10 -, 1,4- and 1,5-quinoid tautomeric complexes of boric acid and borate esters differing by the coordination bonds with carbonyl groups existing in the dynamic equilibrium. The deepening of the reagents color in the presence of boron does not a result only of the complexation, but in the accompanying shift of the tautomeric equilibria.     

A general approach toward the synthesis of C-nucleoside pyrazolo[1,5-a]-1,3,5-triazines and their 3',5'-bisphosphate C-nucleotide analogues as the first reported in vivo stable P2Y(1)-receptor antagonists

In our effort to identify potent purinergic P2Y(1) receptor antagonists as potent platelet aggregation inhibitors with enhanced metabolic stability, we developed an efficient route for the large-scale preparation of 2'-deoxy-C-nucleosides of pyrazolo[1,5-a]-1,3,5-triazine. The key strategic elements of this novel synthetic approach involved the following: (i) the use of a novel activating group, the N-methyl-N-phenylamino group, which was easily generated in high yield by treatment of the pyrazolo[1,5-a]-1,3,5-triazin-4-one (5) with phosphorus oxychloride and dimethylaniline under high pressure, (ii) a regio- and stereospecific palladium-mediated coupling reaction of the readily available unprotected glycal 1,4-anhydro-2-deoxy-D-erythro-pent-1-enitol (4b) and the 8-iodo derivative (16), and (iii) the stereoselective reduction of the ketone group of the furanosyl ring followed by the subsequent displacement of the N-methyl-N-phenylamino group upon treatment with methylamine. The beta configuration at the anomeric C-1' position of the glycal moieties was perfectly retained throughout this conversion. This procedure afforded 8-(2'-deoxy-beta-D-ribofuranosyl)-2-methyl-4-(N-methylamino)pyrazolo[1,5-a]-1,3,5-triazine (21) and 8-(2'-deoxy-beta-D-xylofuranosyl)-2-methyl-4-(N-methylamino)pyrazolo[1,5-a]-1,3,5-triazine (24) with an overall yield of 50% and 39%, respectively. Finally, the conversion of nucleosides 21 and 24 to the pyrazolotriazine C-nucleotides 3',5'-bisphosphate 2 and 3',5'-cyclophosphate 26 is also described herein and represents the first reported nucleotide derivatives within the pyrazolo[1,5-a]-1,3,5-triazine series. Preliminary biological testing has shown that compound 2 strongly inhibits ADP-induced human platelet aggregation and shape change and possesses significant efficacies 30 min after injection in rat, highlighting a strong P2Y(1)-receptor antagonist activity in vitro combined with a prolonged duration of action in vivo.