Viscous and dielectric properties of α-tocopherol and α-tocopherol acetate

This article presents the results of the shear viscosity and the dielectric relaxation measurements performed for α-tocopherol and α-tocopherol acetate, two principal compounds from the vitamin E group. The temperature dependence of the viscosity and dielectric relaxation time of the compounds can be very well reproduced with the Vogel–Fulcher–Tammann equation. It was found that for both tocopherols, the viscosity and the relaxation time attain their infinite high value (solid-like state) at the temperature of ～60 K below the transition to the glass state.     

Organocatalytic synthesis of α-hydroxy and α-aminophosphonates

A new and highly flexible procedure is described for the synthesis of α-amino- and α-hydroxy phosphonates. In the presence of a catalytic amount of oxalic acid (10 mol %), trimethyl phosphite reacts with aldehydes or imines (generated in situ from an aldehyde and an amine) to yield the corresponding coupled products in good yield.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Accessing Cationic α-Silylated and α-Germylated Phosphorus Ylides

The synthesis and full characterization of α-silylated (α-SiCPs; 1 – 7 ) and α-germylated (α-GeCPs; 11 – 13 ) phosphorus ylides bearing one chloride substituent R₃PC(R¹)E(Cl)R²₂ (R=Ph; R¹=Me, Et, Ph; R²=Me, Et, iPr, Mes; E=Si, Ge) is presented. The molecular structures were determined by X-ray diffraction studies. The title compounds were applied in halide abstraction studies in order to access cationic species. The reaction of Ph₃PC(Me)Si(Cl)Me₂ ( 1 ) with Na[B(C₆F₅)₄] furnished the dimeric phosphonium-like dication [Ph₃PC(Me)SiMe₂]₂[B(C₆F₅)₄]₂ ( 8 ). The highly reactive, mesityl- or iPr-substituted cationic species [Ph₃PC(Me)SiMes₂][B(C₆F₅)₄] ( 9 ) and [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) could be characterized by NMR spectroscopy. Carrying out the halide abstraction reaction in the sterically demanding ether iPr₂O afforded the protonated α-SiCP [Ph₃PCH(Et)Si(Cl)iPr₂][B(C₆F₅)₄] ( 6 dec ) by sodium-mediated basic ether decomposition, whereas successfully synthesized [Ph₃PC(Et)SiiPr₂][B(C₆F₅)₄] ( 10 ) readily cleaves the F−C bond in fluorobenzene. Thus, the ambiphilic character of α-SiCPs is clearly demonstrated. The less reactive germanium analogue [Ph₃PC(Me)GeMes₂][B{3,5-(CF₃)₂C₆H₃}₄] ( 14 ) was obtained by treating 11 with Na[B{3,5-(CF₃)₂C₆H₃}₄] and fully characterized including by X-ray diffraction analysis. Structural parameters indicate a strong C_Ylide−Ge interaction with high double bond character, and consequently the C−E (E=Si, Ge) bonds in 9 , 10 and 14 were analyzed with NBO and AIM methods.     

Palladium-catalyzed Hiyama couplings of α-silylenoates and α-silylenamides

The Hiyama couplings of both α-silylenoates and α-silylenamides are described. These sensitive substrate classes require particularly specific conditions, employing both appropriate silicon-based species and a silver additive to realize high yields of the coupling products. Regioselective platinum-catalyzed hydrosilylations provide a direct and convenient entry into these stereodefined trisubstituted alkenes.     

Reaction of nitroalkanes with levoglucosenone and its α-bromo and α-iodo derivatives. Cyclopentaannulation of α-halocyclenones

Michael reactions of levoglucosenone and its α-bromo and α-iodo derivatives with α,ω-dinitroalkanes were studied under conditions of chemical and electrochemical generation of base. Procedures were developed for stereospecific fusion of a cyclopentane ring to α-bromo- and α-iodolevoglucosenones, 2-iodocyclopent-2-en-1-one, and 2-iodocyclohex-2-en-1-one by the action of 2,2-dimethyl-1,3-dinitropropane.     

Click-chemistry approach to isoxazole-containing α-CF3-substituted α-aminocarboxylates and α-aminophosphonates

A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes.     

Scope and Limitations in the Use of α-Silyl and α-Stannyl Sulfones as Latent α-Sulfonyl Anions

Three methods for the regeneration of α-sulfonyl anions from α-silyl sulfones and α-stannyl sulfones are investigated. These methods include: (1) treatment of α-silyl sulfones with electrophiles (aldehydes and acid halides) in the presence of fluoride ion; (2) reaction of α-silyl sulfones with n-butyllithium which produces an α-silyl anion via a migration of the -SiMe₃ group from the α-position to the ortho-position of the phenyl sulfones; and (3) direct transmetalation of α-stannyl sulfone by treatment with n-butyllithium. The addition of cerium [III] chloride is shown to substantially decrease enolization problems associated with addition of α-sulfonyl anions to carbonyl compounds bearing enolizable protons.     

Synthesis of new dialkyl α-aminophosphonates and dialkyl α-aminothiophosphonates

New dialkyl α-aminophosphonates and α-aminothiophosphonates were synthesized by reactions of dialkyl phosphites orO,O-dialkyl thiophosphites withN-benzylidene 2-(vinyloxy)ethylamine orN-(4-fluorobenzylidene)-2-(vinyloxy)ethylamine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1815–1817, September, 1999.     

Catalytic chemodivergent annulations between α-diketones and alkynyl α-diketones

Four types of unprecedented and chemodivergent reactions between α-diketones and alkynyl α-diketones have been achieved under the catalysis of phosphine and Br?nsted base, respectively, leading to the rapid construction of four different classes of biologically important but synthetically challenging molecular scaffolds including 2-hydroxyfuran-3(2H)-ones, 4-hydroxy-2-oxabicyclo[2.2.1]heptan-3-ones, 1,3-diaryl cyclobutanes, and 4-(furan-2(3H)-ylidene)cyclopent-2-enones. The formation of the products includes two novel rearrangement processes, and further transformations on the products can be easily achieved to deliver value-added substances such as highly functionalized cyclopentanes. Moreover, the 2-hydroxyfuran-3(2H)-one products display promising photophysical properties such as green luminescence under UV light and aggregation-induced emission effect,showing the practical application value of this work. The great potential of α-diketones in both synthetic chemistry and material science has been unambiguously demonstrated.     

Regiospecific synthesis of α-chloro- and α-fluoro-1,2-diones

α-Chloro-1,2-diones and α-fluoro-1,2-diones were prepared from the corresponding α-chloroaldimines by a sequence of reactions involving cyanation to α-cyanoenamines, α-halogenation to form α-chloro- or α-fluoroimidoyl cyanides and addition of organolithium reagents across the nitrile moiety, followed by acidic hydrolysis. All steps are straightforward and occur without side reactions finally leading to regiospecifically chlorinated and fluorinated 1,2-diones in good yields.     

Copper-catalyzed diversified annulations between α-diketones and alkynyl α-diketones

Copper-catalyzed divergent annulations between α-diketones and alkynyl α-diketones have been achieved, delivering a series of highly functionalized and biologically important cis-hexahydro-2Hcyclopenta[b]furan(HCPF) and 2-hydroxydihydrofuran-3(2H)-one(HDFO) products with high levels of stereoselectivity under identical conditions. The protocol features the use of earth-abundant copper catalyst, mild conditions, shortening synthetic routes in constructing different molecular frameworks, and reduc...     

New general synthesis of α-alkoxyketones via α'-alkylation, α-alkylation and α,α'-dialkylation of α-alkoxyketimines

α-Methoxy- and α-ethoxyketones, as important intermediates in organic synthesis and flavor compounds in food chemistry, were synthesized by deprotonation of N-(1-alkoxy-2-propylidene)isopropylamine, prepared by condensation of the corresponding α-alkoxyacetone with isopropylamine, and subsequent reaction of the corresponding 1-azaallylic anions with alkyl halides to afford α'-alkylated, α-alkylated and α,α'-dialkylated ketimines. Hydrolysis of the imino function led to the desired substituted α-alkoxyketones. The ratio of α-, α'-, and α,α'-(di)alkylated compounds depended on the amount of base used and on the nature of the alkylating reagent.     

Synthesis of new racemic α-heterocyclic α,α-diaminoesters and α-aminoester carboxylic

New racemic α-aminoester and α,α-diaminoesters derivatives were synthesized by nucleophilic substitution of methyl α-azido glycinate N-benzoylated with 3-amino-1,2,4-triazole, 2-tetrahydrofuran-2-ylmethan-amine and 2-methyl quinolin-4-amine.     

Copolymerization of α-Methylstyrene and Styrene

In this paper, the effects of temperature from 60 °C to 80 °C and the molar ratios in monomer feed on the copolymerization of α-methylstyrene(AMS) and styrene(St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75 °C, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St = 50/50(molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as-AMS-AMS-AMS-,-St-AMS-AMS-(-AMS-AMS-St-) and-St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9 °C(0 mol% AMS) to 250.2 °C(42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMScontaining sequences which could be used as potential free radical generators.     

Synthesis of α-alkyl- and α,α-dialkyl-β-phenyltryptamines

A new method was developed for the synthesis of -alkyl- and ,-dialkyl--phenyltryptamines based on alkylation of nitroalkanes with -phenyl-nor-gramine.     

Synthesis of α-amino oximes and bis-α-amino oximes from the monoterpene hydrocarbons 3-carene and α-pinene and α,ω-diamines

The reaction of nitroso chlorides of natural monoterpene hydrocarbons, 3-carene and -pinene, with simple ,-diamines (1,2-diaminoethane, 1,3-diaminopropane, piperazine, 1,6-diaminohexane, diethylenetriamine) results in the formation of -amino oximes and bis--amino oximes. The product structures were proved by spectroscopy. The procedures of separation and purification of diamino oximes and diamino dioximes are described. Detailed analysis of the ¹H and ¹³C NMR spectra of the new chiral nitrogen-containing derivatives was carried out.     

Short and efficient hemisynthesis of α-eudesmol and cryptomeridiol

The aerial part of Dittrichia viscosa yielded two sesquiterpenes, isocostic acid (1) and ilicic acid (2), on multigram scale. These acids are appropriate starting materials for short and facile syntheses of α-eudesmol (5) and cryptomeridiol (6), natural products featuring anti-Alzheimer and anti-spasmodic properties. Compounds 5 and 6 were obtained in three steps in overall yields of 70% and 52%, respectively.