A facile route to isoflavone quinones via the direct cross-coupling of chromones and quinones

A straightforward and efficient method for the palladium-catalyzed direct cross-coupling of chromones with various quinones has been developed to rapidly construct isoflavone quinone structural motifs.     

Reaction of vinylogs of a Fischer base with salicylaldehydes

The reaction of vinylogs of the Fischer base, viz., 1,3,3-trimethyl-2-(3-methyl-2-buten-1-ylidene) indoline, 1,3,3-trimethyl-2-(2-penten-1-ylidene) indoline, 1,3,3-trimethyl-2-(3-phenyl-2-propen-1-ylidene) indoline, and 1,3,3-trimethyl-2-(2-buten-1-ylidene) indoline, with salicylaldehydes commences with displacement by the aromatic o-hydroxy aldehyde of the vinyl part of the dienamine molecule, as a result of which the usual spirobenzopyran is formed. In the case of the first two dienamines the reaction stops at this stage, whereas in the latter two a second molecule of dienamine adds to the initially formed spirobenzopyran at the double bond of the pyran ring to give dicondensed spirochromans.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 649–653, May, 1981.     

A facile synthetic route to 2-trifluoromethyl-substituted polyfunctionalized chromenes and chromones

A method for the preparation of methyl 4-hydroxy-2-(trifluoromethyl)-4H-chromenes-3-carboxylate derivatives 3a–j from readily available trifluoromethylated building block methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate 1 was described. Treatment of 3a–j with Sarrett reagent in CH₂Cl₂ generated methyl 4-oxo-2-(trifluoromethyl)-chromene-3-carboxylate derivatives 4a–h with moderate to good yields, which can be converted to 2-trifluoromethyl-substituted multifunctional benzoxepins through cyclopropanation and Lewis acid-catalyzed ring opening.     

Synthesis of 2, 2-Dimethyl-2H-chromenes via a Palladium (II) Catalysed Reaction

The antijuvenile hormones Precocene-I, Precocene-II and other bioactive 2, 2-dimethyl-2H-chromenes have been synthesised by intramolecular oxidative cyclisation of 2-isoprenyl phenols catalysed by a palla-dium(II) salt.     

Ethyl 2,4-dioxoalkanoates as starting materials for a convenient route to 3(2H) furanones and 3(2H) furanimines

Addition of both Grignard reagents or hydride reducing agents to the ester group of the readily available 2,4-dioxoalkanoates, while the 1,3-diketone fragment is suitably masked both in form of an isoxazole ring or as an enaminone function, allows a useful preparation of a variety of α'-hydroxy-1, 3-diketone moieties. Acid-promoted cyclodehydration of these compounds leads to 3(2H) furanones or 3(2H) furanimines depending on the substitution pattern and on reaction conditions.     

Reaction of tris(alkylthio)cyclopropenyl cations with 2-pyridylmagnesium bromide as a new route to indolizines

The reaction of tris(isopropylthio)- and tris(tert-butylthio)cyclopropenylium perchlorates 1a and 1b with 2-pyridylmagnesium bromide in dry tetrahydrofuran at room temperature gave 1,2,3-tris(isopropylthio)- and 1,2,3-tris(tert-butylthio)indolizines 2a and 2b , respectively, in high yields.     

Cycloadditions with hetaryl dieneamines a direct route to hetarylazulenes

Hetaryl dieneamines readily available from fused N-aryl azolium salts with secondary amines were found to undergo cycloadditions. With N-phenylmaleinimide and acetylene dicarboxylic ester, [4+2] cycloaddition took place to yield tetrahydroisoindolone (2) and phtalic acid (3) derivatives, respectively. Reaction with fulvene reagent4 resulted in a [6+4] cycloaddition followed by a spontaneous elimination and allowed a convenient route to hetaryl azulenes (5–7).     

Reaction of 2-polyfluoroalkylchromones with 1,3,3-trimethyl-3,4-dihydroisoquinolines and methylketimines as a direct route to zwitterionic axially chiral 6,7-dihydrobenzo[a]quinolizinium derivatives and 2,6-diaryl-4-polyfluoroalkylpyridines

[reaction: see text] 2-Polyfluoroalkylchromones react with 1,3,3-trimethyl-3,4-dihydroisoquinolines to give zwitterionic axially chiral 6,7-dihydrobenzo[a]quinolizinium derivatives in high yields. In addition, performing this reaction with aromatic methylketimines is a simple and convenient synthesis of 2,6-diaryl-4-polyfluoroalkylpyridines.     

The homologous tert-amino effect: a route to fused 2-benzazepine derivatives

2-Cyano- and 2-carbethoxy-3-[2-(pyrrolidin-1-ylmethyl)phenyl]acrylonitriles were prepared through either amination of appropriate 3-[2-(bromomethyl)phenyl]acrylonitriles with pyrrolidine or condensation of 2-(pyrrolidin-1-ylmethyl)benzaldehyde with malononitrile and ethyl cyanoacetate. These acrylonitrile derivatives were shown to undergo easy mutual interconversion with 1-(pyrrolidin-1-yl)indane-2-carbonitriles driven by solvent polarity. Upon heating at 140-150 °C both acrylonitrile and indane derivatives were found to give 2,3,5,10,11,11a-hexahydro-1H-pyrrolo[1,2-b][2]benzazepine-11-carbonitriles. All transformations observed were rationalized in the terms of reactions related to the tert-amino effect. Furthermore, the corresponding piperidin-1-yl and azepan-1-yl analogs of the above acrylonitriles and indanes were obtained similarly. By analogy their heating afforded 1,2,3,4,6,11,12,12a-octahydropyrido[1,2-b][2]benzazepine-12-carbonitriles and 7,8,9,10,11,11a, 12,13-octahydro-5H-azepino[1,2-b][2]benzazepine-12-carbonitriles.     

2,3-unsubstituted chromones and their enaminone precursors as versatile reagents for the synthesis of fused pyridines

A divergent and regioselective approach to fused pyridines was developed through formal [3 + 3] cyclocondensations from simple 2,3-unsubstituted chromones or their enaminone precursors.     

Condensation of 2-hydroxyacetophenones with trichloroacetonitrile as a route to 2-trichloromethylchromones and 4-hydroxycoumarins

Condensation of 2-hydroxyacetophenones with trichloroacetonitrile in the presence ofN-methylanilinomagnesium bromide affords hydroxyaryl β-amino-β-trichloromethylvinyl ketones, which are converted into 2-trichloromethylchromones upon treatment with concentrated HCl. The resulting compounds react with alcoholic solutions of NH₃ or KOH to form 3-amino-1-(2-hydroxyaryl)-4,4,4-trichlorobut-2-en-1-ones and 4-hydroxycoumarins, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 476–479, March, 2000.     

An efficient route to 4-substituted coumarins, 2(5H)-furanones, and pyrones via palladium-catalyzed couplings of alkenyl tosylates with organoindium reagents

Highly efficient palladium-catalyzed couplings of alkenyl tosylates with organoindium reagents under mild conditions are described, which give rise to 4-substituted coumarins, 2(5H)-furanones, and pyrones in good to excellent yields.     

Gold-catalyzed 1,2-migration of silicon, tin, and germanium en route to C-2 substituted fused pyrrole-containing heterocycles

An efficient method for the synthesis of fused pyrroloheterocycles from diverse propargyl-substituted heterocycles in the presence of Au-catalyst has been developed. The cascade transformation proceeds via alkyne-vinylidene isomerization with concomitant 1,2-shift of hydrogen, silyl, and stannyl groups. Remarkably, it was also shown that previously unknown 1,2-migration of a germyl group upon alkyne-vinylidene rearrangement occurs under these reaction conditions. This method allows for mild and efficient synthesis of diverse C-2 substituted N-containing heterocycles.     

Reaction of hydroxyfullerene with metal salts: a route to remediation and immobilization

Hydroxylated fullerene reacts rapidly and irreversibly (across a wide pH range) with Fe(NO3)3, Al(NO3)3, CaCl2, CoCl2, CuCl2, KMnO4, Ag(NO3), and ZnCl2 under ambient aqueous conditions to produce insoluble metal-hydroxyfullerene cross-linked polymers (M-fullerenol). Materials have been characterized by SEM, TEM, AFM, XPS, and UV-visible spectroscopy. Molecular mechanics calculations on the model systems, [Fe(C60O2)2] and [Fe(C60O2)3], show that both tetrahedral and octahedral coordination are possible. The rate of precipitation reaction is proportional to the concentration of both reagents. The interaction of hydroxyfullerenes with metals is an important issue with regard to waste treatment, fullerene exposure in the environment, and fullerene-based pharmaceutical agents.     

Reaction of α,α-, α,α′-dihalothiones with 8-mercaptoquinolinium halides as a route to tetrahydro-1,4-thiazinoquinolinium halides

The reaction of 8-mercaptoquinolinium bromide with 1,3-dibromopropane-2-thione or 3,3-dibromobutane-2-thione in methanol gave the 2-bromomethyl-2-mercaptotetrahydro-1,4-thiazino[2,3,3,4-i,j]quinolinium and 3-bromo-2-mercapto-2,3-dimethyltetrahydro-1,4-thiazino[2,3,3,4-i,j]quinolinium bromides which readily exchanged the Br⁻ anion for ClO ₄ ⁻ upon treatment with sodium perchlorate in methanol. Oxidation of the 3-bromo-2-mercapto-2,3-dimethyltetrahydro-1,4-thiazino[2,3,3,4-i,j]-quinolinium bromide by selenium dioxide gave 2,2-dithiobis(3-bromo-2,3-dimethyltetrahydro-1,4-thiazino[2,3,3,4-i,j]quinolinium) bromide. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1720–1723, November, 2006.     

A desymmetrization route to fused Troger's base analogues: synthesis, isolation, and characterization of the first anti-anti diastereomer of a fused tris-Troger's base analogue

A desymmetrization route to fused Troger's base analogues was developed. In this way, the synthesis of the first example of an anti-anti diastereomer of a fused tris-Troger's base analogue was accomplished. The resulting compound 5b is a nonlinear symmetric regioisomer obtained from p-bromoaniline in 7% yield. The corresponding syn-anti diastereomer 5a was obtained in 4% yield.