Syntheses and Structure of Potassium α-and β-Trivanadoenneatungstogermanates

Potassium α-and β-trivanadoenneatungstogermanates were prepared and characterized by means of elemental analysis, IR, 51V and 183W NMR spectra and polarography. The single crystal structure of a-isomer was determined. The final R is 0. 083. The results show that two prepared heteropoly anions have Keggin structure, and a-isomer belongs to A-type and has stronger oxidizing ability than β-isomer.     

Convenient Syntheses of Perdeuterioacrylonitrile and β,β-Dideuterioacrylonitrile

Perdeuterioacrylonitrile can be prepared conveniently from succinonitrile in a two-step process. Succinonitrile is exchanged with D₂O to obtain perdeuteriosuccinonitrile, which is then pyrolyzed at ～550°C to obtain perdeuterioacrylonitrile and DCN. CDBCN and CzDsCN are by-products of this reaction. A chemical procedure for separating perdeuterioacrylonitrile from these materials was developed. This involved formation of the Diels-Alder adduct of cyclopentadiene with perdeuterioacrylonitrile, followed by pyrolysis of the purified adduct at -330°C. Cyclopentadiene was removed from the resulting pyrolyzate by reaction with maleic anhydride. Purified perdeuterioacrylonitrile exchanged with H₂O to yield β,β-dideuterioacrylonitrile in good yield and good isotopic purity.     

Facile Syntheses and Desulfonylation of α-Alkyl- β-disulfones

Introduction Recently more attention has been paid to the application of sulfones to organic synthesis. Because the arylsulfonyl groups can stabilize adjacent carbanions and may be removed by reduction and elimination, the arylsulfonyl groups could be used as activating group for alkylation, acvlation or addition reaction.     

Synthesis and substitution reactions of β-alkoxyvinyl bromodifluoromethyl ketones

β-Alkoxyvinyl bromodifluoromethyl ketones 1a, 1b and 1c were synthesized by the reaction of bromodifluoroacetic anhydride with appropriate vinyl ethers in high yields. The acyclic enone 1a reacted with amines to give the corresponding β-aminovinyl bromodifluoromethyl ketones 2 in good yields. The reaction of 1a with electrophilic reagent ICl yielded α-iodoenone 4. The substitution reaction of the cyclic enones 1b and 1c with thio-nucleophiles gave the corresponding difluoromethylene thioethers 6. The three-component reactions of 2 with primary amines and formaldehyde gave multifunctional 1,2,3,4-tetrahydropyrimidine 3 in moderate yields.     

Nitration reactions of astaxanthin and β-carotene by peroxynitrite

The in vitro reactivities of astaxanthin and β-carotene toward peroxynitrite were investigated and the reaction products after scavenging with peroxynitrite were analyzed. A series of carotenoids substituted with nitro group, 14′-s-cis-15′-nitroastaxanthin, 10′-s-cis-11′-cis-11′-nitroastaxanthin, 14′-s-cis-15′-nitro-β-carotene and 10′-s-cis-11′-cis-11′-nitro-β-carotene, were isolated from the reaction products of carotenoids with peroxynitrite. Carotenoids with nitro derivatives were reported for the first time. These results indicated that astaxanthin and β-carotene could catch peroxynitrite or nitrogen dioxide radical (NO₂) in their molecule to form nitrocarotenoids.     

Syntheses with pyridinium and sulfonium salts of acylated β-enaminonitriles

Summary Pyridinium and sulfonium salts2a–e which can be prepared from 3-amino-2-(-haloacetyl)-crotonitriles and 3-amino-2-(-halo-acetyl)-3-phenyl-acrylonitriles react with malononitrile in the presence of a base to 3-amino-2-pyridinio-phenolates3a,b and 3-amino-2-sulfonio-phenolates3c–e. In an analogous way, 3-amino-2-(diethyloxyphosphoryl)-phenol5a and 3-amino-2-(p-tolyl-sulfonyl)-phenol5b have been prepared. 2,3-Diamino-phenoles6a,b are formed from the pyridinium salts3a,b. The behaviour of the pyridinium salts2a,b towards heterocumulenes has been investigated. Cyanamide leads to the (2-amino-4-hydroxy-pyrid-3-yl)-pyridinium salt8c. Phenylisothiocyanate gives the 3-pyridinio-2-thioxo-pyridin-4-olates9a,b. Carbon disulfide gives rise to 3-pyridinio-2-thioxo-pyridin-4-olate10 or 3-pyridinio-2-thioxo-thiopyran-4-olate11, depending on the substituent at the 6-position. Phenylisocyanate reacts to the pyrimidin-2,4-dione12 with loss of N-methyl-pyridinium chloride. S-methylation of9a and cleavage of the pyridine moiety yields the 3-amino-2-methylthio-pyrid-4-one14. The structures were investigated by¹H and¹³C NMR spectroscopy.

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Synthesen mit Pyridinium- und Sulfoniumsalzen von acetylierten -Enaminonitrilen

Zusammenfassung Pyridinium- und Sulfoniumsalze2a–e, die aus 3-Amino-2-(-halo-acetyl)-crotonsäurenitril und 3-Amino-2-(-halo-acetyl)-zimtsäurenitril hergestellt werden können, reagieren mit Malonsäuredinitril in Gegenwart einer Base zu 3-Amino-2-pyridinio-phenolaten3a,b und 3-Amino-2-sulfonio-phenolaten3c–e. In Analogie wurden 3-Amino-2-(diethyloxyphosphoryl)-phenol5a und 3-Amino-2-(p-tolyl-sulfonyl)-phenol5b erhalten. 2,3-Diamino-phenole6a,b werden aus den Pyridiniumsalzen3a,b gebildet. Das Verhalten der Pyridiniumsalze2a,b gegenüber Heterokumulenen ist untersucht worden. Cyanamid führt zum (2-Amino-4-hydroxy-pyrid-3-yl)-pyridiniumsalz8c. Phenylisothiocyanat liefert die 3-Pyridinio-2-thioxo-pyridin-4-olate9a,b. In Abhängigkeit vom Substituenten in der Position 6 entsteht bei der Reaktion mit Schwefelkohlenstoff ein 3-Pyridinio-2-thioxo-pyridin-4-olat10 oder ein 3-Pyridinio-2-thioxo-thiopyran-4-olat11. Phenylisocyanat reagiert zum Pyrimidin-2,4-dion12 unter Verlust von N-Methyl-pyridiniumchlorid. S-Methylierung von9a und Spaltung des Pyridiniumringes ergibt das 3-Amino-2-methylthio-pyrid-4-on14. Die Verbindungen wurden¹H- und¹³C-NMR-spektroskopisch untersucht.

     

Syntheses of α-pyrones using gold-catalyzed coupling reactions

Sequential alkyne activation of terminal alkynes and propiolic acids by gold(I) catalysts yields compounds having α-pyrone skeletons. Novel cascade reactions involving propiolic acids are reported that give rise to α-pyrones with different substitution patterns.     

Enzymatic Syntheses of N-Acetyllactosamine and N-Acetylallolactosamine by the Use of β-D-Galactosidases

Abstract

A β-D-galactosidase from Bacillus circulans induced β-D-galactopyranosyl transfer from lactose predominantly to a secondary (OH-4) rather than the primary hydroxyl group (OH-6) of 2-acetamido-2-deoxy-D-glucopyranose. 4-O-β-D-Galacto-pyranosyl-2-acetamido-2-deoxy-D-glucopyranose (N-acetyl-lactosamine) was thus readily synthesized on a gram scale and conveniently isolated by chromatography on a column of charcoal-Celite. On the other hand, the glycosyl transfer to the 6-position predominantly was efficiently induced to give 6-O-β-D-galactopyranosyl-2-acetamido-2-deoxy-D-glucopyranose (N-acetyl-allolactosamine) by consecutive use of β-D-galactosidases from Kluyveromyces lactis and B. circulans. These enzyme reactions were efficient enough to allow the one-pot preparation of the desired disaccharides.     

Syntheses of β-Mannopyranosedes by Enzymatic Approaches

Abstract

The transmannosylation activity of β-mannosidase from snail and β-galactosidase from Aspergillus oryzae was used for the synthesis of methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 1-hexyl, cyclohexyl, and 1-octyl β-D-mannopyranosides (3a-i), respectively. The regioisomeric specificities and wide substrate acceptance of this galactosidase are demonstrated. Thus, 4-nitrophenyl 4-O-(α-D-glucopyranosyl)-β-D-glucopyranoside (6), 4-nitrophenyl 2-O-(β-D-glucopyranosyl)-β-D-glucopyranoside (7), 4-nitrophenyl 2-deoxy-2N-acetyl-6-O-(2-deoxy-2-N-acetyl-β-D-glucopyranosyl)-β-D-glucopyranoside(8),4-nitropheny 13-O-(β-D-mannopyranosyl)-α-D-mannopyranoside (9), and 4-nitrophenyl 4-O-(β-D-mannopyranosyl)-β-D-mannopyranoside (10) were prepared by chemoenzymatic self-transfer reaction.     

Aminoselenenylation of olefins. Syntheses of β-phenylseleno carbamates

(β-Phenylseleno carbamates have been synthesized by reaction of olefins with phenylselenenyl chloride and carbamates in presence of silver tetrafluoroborate. This reaction constitutes a good method for the conversion of olefins to β-functionalized protected amines.     

Syntheses of Benzoxepinoquinolinone and Benzothiepinoquinolinone

l-Benzoxepino(3, 4-b)quinolin-l3(6H)-one and its halogen,alkyl, alkoxy derivatives Va'-d' and 1-benzothiepino(3,4-b}-quinolin- 13 ( 6H)-one Vf, and its alkyl derivatives Vg, weresynthesized through cyclization of 2-(substituted phenoxymethyl)-3-quinolinecarboxylic acids Va-d and 2-[ (un)substituted phen-ylthiomethyll-3-quinolinecarboxylic acids IVf-g in the presence ofpolyphosphoric acid.The acids IV were obtained from the corresponding ethyl-esters @ whcih were prepared through refluxing ethyl 2-bromo-methyl-3-quinolinecarboxylate(1) with substituted phenol or (un)substituted thiophenol in the presence of NaOEt.The compound Vg, was allowed to react with NBS, KaBH4, NH2OH-HCl to give compounds VII , VIII, and IX, respectively.The structures of 24 new compounds have been confirmed by elemental analysis, IR and 1H NMR.     

Syntheses, structure and ethylene polymerization behavior of β-diiminato titanium complexes

A series of new titanium complexes bearing β-diiminato ligands [(Ph)NC(R₁)CHC(R₂)N(Ph)]₂TiCl₂ (4a: R₁ = R₂ = CH₃; 4b: R₁ = R₂ = CF₃; 4c: R₁ = Ph, R₂ = CH₃; 4d: R₁ = Ph, R₂ = CF₃) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4a and 4c adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4a-d are active catalysts for ethylene polymerization, and produce high molecular weight polyethylenes. Catalyst activities and the molecular weights of polymers are considerably influenced by the steric and electronic effects of substituents on the catalyst backbone under the same polymerization condition. With the strong electron-withdrawing groups (CF₃) at R₁ or/and R₂ position, complexes 4b and 4d show higher activities than complexes 4a and 4c, respectively.     

Efficient Syntheses of 2-Substituted Benzimidazoles and Benzoxazoles from β-Keto Esters

An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products.     

Metathesis reactions of β-acyloxysulfones: synthesis of 1,6- and 1,7-dienes

A novel alkene-masking strategy has been developed that allows for a metathesis approach to 1,6- and 1,7-dienes. This method was successfully applied to the synthesis of a long-chain alkenone natural product.     

Synthesis of 2,5-dihydropyridine derivatives by gold-catalyzed reactions of β-ketoesters and propargylamines

The reaction of simple β-ketoesters and propargylamines under gold(III) catalysis leads to the formation of the elusive 2,5-dihydropyridine system. This new reaction provides the synthesis of potentially bioactive compounds in moderate to high yields.     

The reactivity of tert-butoxyl radicals in reactions of hydrogen abstraction and β-elimination

The transition states of competing reactions of abstraction of the H atom from hydrocarbon molecules by tert-butoxyl radical and its -elimination were studied by the semiempirical quantum-chemical AM1 method. The calculated activation enthalpy and entropy of these reactions correlate with the experimental values. A correlation between the reactivity in homolytic hydrogen abstraction and the parameters of the chemical structure of the reactants was found.     

Syntheses Characterization of Chloro-cyclopentadienyltricarbonyl-molybdenum with β-Cyclodextrin Supramolecular

Organotransition metal complex have been extensively used as homogeneous catalysts in organic reactions and much effort has been paid to improve their activity and selectively. Cyclodextrins have been studied as a model of enzyme for selective catalysis. However, so far there are only a few reports on the inclusion compounds of organometallic complexes with cyclodextrins. Breslow et al.repored high acylation rates for β-CD using ferrocene derivatives and assumed β-CD substrate complexes as intermediate [1]..larad et al reported the preparation and propertics of cyclodextrin-ferrocen inclusion compounds as the first example of cyclodextrin inclusion compounds of organotransition metal complexes[2]. Song Le-Xin et al reported the supramolecular inclusion compound of β-cyclodextrin with cyclopentadieny-tricarbonylmanganese [3] .To our knowledge, there are no reports of inclusion compounds of β-CD with molybdenum organometallic complexes. In the present work we described the preparation and properties of the supramolecular of CpMo(CO)3Cl with β-CD in details.     

Syntheses of β－Hydroxy Ketones by Organosamarium

An organosamarium reagent was prepared via the reaction of a-bromoacetophenone with samarium. This organosamarium reagent reacted with aldehydes to give β-hydroxy ketones. A possible reaction process was suggested.