Synthesis of optically active α-(allenyl)- and α-substituted-α-(allenyl)glycines

The synthesis of various types of optically active α-(allenylsilane-containing)glycines via a chirality-transferring ester-enolate Claisen rearrangement of α-acyloxy-α-alkynylsilanes is described. The conversion of the rearranged products into the optically active silicon-free α-(allenyl)- and α-substituted-α-(allenyl)glycines was achieved by the removal of the Me₂PhSi- or TMS group from the allene terminus.     

Synthesis and properties of α, α′ -bis -(p-benzylphenyl)xylene

Summary ,-bis-(p-Benzylphenyl)xylene was synthesized for the first time and its UV and infrared spectra determined.     

A direct synthesis of α-(hydroxymethyl) and α-alkyl-vinyl alkyl ketones

Reaction of 2,4-diketoesters 3a-c with aqueous formaldehyde using potassium carbonate solution as base affords the corresponding α-methylene-β-hydroxyalkanones 4a-c which provide a route to α,β-unsaturated alkyl ketones 6a-e via coupling of α-acetoxymethyl alkyl vinyl ketone 5a with Grignard reagents in the presence of a catalytic amount of LiCuBr₂ at low temperature.     

3-(α-Nitroalkyl- and α-polynitroalkyl-ONN-azoxy)-4-nitraminofurazans and some their derivatives

Methods for the preparation of 3-(α-nitroalkyl- and α-polynitroalkyl-ONN-azoxy)-4-nitraminofurazans with primary and secondary nitramine groups and their derivatives, including N,N′-bis[(3-(α-polynitromethyl-ONN-azoxy)furazan-4-yl]alkylen-N,N′-dinitramines, have been elaborated.     

Synthesis and Reactivity of α-Bromo-4-(difluoromethylthio)acetophenone

A synthesis is reported for -bromo-4-difluoromethylthioacetophenone and the conditions for the condensation of this compound with 2-aminothiazole, 2-amino-5-chloropyridine, 2-amino-4,5-dihydro-3H-pyrrole, benzimidazoline-2-thione, oxadiazoline-2-thione, and thiourea were studied. S- and N-substituted azaheterocycles containing the 4-(difluoromethylthio)phenyl fragment were synthesized and characterized.     

Cyclization of α- and β-amino ketones. (Review)

In this review data on the synthesis of three-, four-, five-, and six-membered heterocycles, as well as of condensed heterocyclic compounds from -amino ketones and Mannich bases are classified for the first time.Samara State Technical University, Samara 433100, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 723–735, June, 1999.     

Indole derivatives. 138. Synthesis of α-(5-indolyl)ethylamine and 5-(2-aminoethoxy)- and 5-(aminoethylthio)tryptamines

The reaction of 5-acetylindole with hydroxylamine with subsequent reduction of the resulting oxime gave -(5-indolyl)ethylamine. Coupling of 4-(2-phthalimidoethoxy)- and 4-(2-phthalimidoethylthio)phenyldiazonium chlorides with ethyl -acetyl--phthalimidovalerate, subsequent cyclization of the resulting hydrazones, hydrolysis, decarboxylation, and removal of the phthalyl protecting group led to the formation of 5-(2-aminoethoxy)- and 5-(2-aminoethylthio)tryptamines, respectively.For Communication 137, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 46–48, January, 1992.     

Multigram Synthesis of α- and γ-((Hetera)cyclo)alkylpyridines through α-Arylation of (Hetero)aliphatic Nitriles

A systematic study on the S_nAr reaction of halogenated fluoropyridines and (hetero)aliphatic nitrile anions as an approach to the synthesis of functionalized pyridines bearing a (cyclo)alkyl or saturated heterocyclic substituent by is described. The scope of the method was demonstrated on a wide range of (hetero)aliphatic nitriles (including three- to six-membered cycloalkane derivatives and N-, O-, S-containing saturated heterocycles) and all isomeric halogenated 2-and 4-fluoropyridines. High chemo- and regioselectivity (i. e., exclusive substitution of the fluorine atom), as well as excellent scalability of the proposed reaction sequence were demonstrated (up to 450 g for the arylation step or up to 77 g of cycloalkylpyridine over two steps in a single run). The utility of the synthesized products was illustrated in the additional functional group transformations resulting in synthetically valuable pyridine-containing building blocks.     

Synthesis of α-(perfluoroalkyl)-ω-(trialkylsilyl)alkanols

The synthesis of alkanols of the general formula R₃Si(CH₂)_nCH(OH)R_F (n = 1–3) is elaborated and their behavior under GC-MS is studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1516-1519, June, 1996.     

Synthesis of Eudesmanolides Possessing Denebutenolide and Endocyclic α,β-Unsaturated Butenolide from α-(-)-Santonin

A new and efficient method of double bond functionalization of eudesmanolide was carried out by rearrangement of epoxide with methoxide. which is important to synthesis of bioactive natural products containing denebutenolid (1) and endocyclic α, β -unsaturated butenolide (2).     

Synthesis and Crystal Structure of α-(3-Phenylureido)-α-(2,4-Dichlorophenyl) Methyl Phenylphosphinic Acid

1INThODUCT1ONInaprevi0uspaPer"',wereP0rtedthesyntheses0fsome1,3,4-diazaphospho-lidin-2-thione-4-oxidesandtheirhighselectiveherbicidalactivity.Althoughtherewereseveralreportsaboutthedesulphurisationofsomestraightchainthioureaderiva-tivest2'31,uptonow,thedesulphurisationreactionofcyclicthioureaderivativesutiliz-ingAgNO,-H,Osystemhasnotbeenstudied.InthispaPer,thedesulphurisation0fcis-3,4-diphenyl-5-(2,4-dichlorophenyl)-1,3,4-diazaphOSpholidin-2-thione-4-oasthecyclicsubstrateisrep0rtedfort…     

Enantioselective total syntheses of (-)-taiwaniaquinone H and (-)-taiwaniaquinol B by iridium-catalyzed borylation and palladium-catalyzed asymmetric α-arylation

We report a concise, enantioselective total synthesis of (-)-taiwaniaquinone H and the first enantioselective total synthesis of (-)-taiwaniaquinol B by a route that includes asymmetric palladium-catalyzed α-arylation of a ketone with an aryl bromide that was generated by sterically controlled halogenation via iridium-catalyzed C-H borylation. This asymmetric α-arylation creates the benzylic quaternary stereogenic center present in the taiwaniaquinoids. The synthesis was completed efficiently by developing a Lewis acid-promoted cascade to construct the [6,5,6] tricyclic core of an intermediate common to the synthesis of a number of taiwaniaquinoids. Through the preparation of these compounds, we demonstrate the utility of constructing benzylic quaternary stereogenic centers, even those lacking a carbonyl group in the α-position, by asymmetric α-arylation.     

Concise Synthesis of α-(Hydroxymethyl) Alkyl and Aryl Vinyl Ketones

2,4-Diketoesters 2 have first been reported as starting materials for the synthesis of a new class of α-hydroxymethyl-α,β-unsaturated ketones 3. Thus, under heterogeneous liquid–liquid medium in the presence of concentrated aqueous potassium carbonate as a base, both aliphatic and aromatic 2,4-dioxoalkanoates 2 react with aqueous formaldehyde to afford the corresponding ketones 3 in fair to good yields.     

On the properties of the anions derived from α-deprotonation of α-(o-carboran-1-yl)- and α-ferrocenyl-1-alkylbenzotriazoles

The synthesis of 1-[(2-R-o-carboran-1-yl)methyl]benzotriazoles (R = Me, Ph) is described. α-Deprotonation of these compounds followed by reactions of the generated carbanions with MeI give the corresponding α-methylated products. Even at room temperature, they exist in solution as an equilibrium mixture of two conformers due to steric crowding around the C^α atom. In contrast, the anions generated by deprotonation of α-ferrocenyl derivatives of 1-methyl- and 1-ethylbenzotriazoles are ambident and are attacked by electrophiles at both the C^α and N(3) atoms.     

Rearrangement of enol acetates of α-(3,5-dimethyl-1,2,4-triazol-1-yl)-2,4-dichloroacetophenone and α-(1,2,4-triazol-1-yl)-2,4-dichloropropiophenone

At 140 °C in acetic anhydride enol acetates of -(3,5-dimethyl-1,2,4-triazol-1-yl)-2,4dichloroacetophenone and -(1,2,4-triazol-1-yl)-2,4-dichloropropiophenone undergo 1,3and 1,5-rearrangement, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 182–184, January, 1995.     

Synthesis of α- and β-Methyl NEU5Ac α-(2→8) NEU5Ac Disaccharides

ABSTRACT

Acid hydrolysis of colominic acid, an α-(2→8)-linked oligomer of sialic acid, yielded Neu5Ac α-(2→8) Neu5Ac (di-Neu5Ac) 2 as one of the products. Starting from this disaccharide, it was possible to prepare two potential di-Neu5Ac donors, 5 and 8, as their corresponding 2-chloro derivatives. Subsequent reaction of the donor 8 with methanol as a simple acceptor led to the α- and β-methyl Neu5Ac α-(2→8) Neu5Ac glycosides.     

α-hydroaxyalkyl(benzyl)furozans and α-hydroxyalkyl(benzyl)furoxans synthesis and reactivity

A general and simple preparative method for the synthesis of -hydroxyalky(benzyl)furazan and -furoxan derivatives is proposed, The method involves reduction of acyl or ethoxycarbonyl substituents in these heterocyclic compounds with NaBH₄ in ethanol. Based on the alcohols thus prepared, a number of previously unknown functional derivatives (-nitroxyalkyl--haloalkyl-, and -azidoalkylfurazans and -furoxans) have been synthesized.Translated fromInvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7. pp, 1782–1788, July, 1996.     

Copper(II) and oxovanadium(IV) complexes of α-hydroxymethylserine

Summary Potentiometric and spectroscopic measurements were used to characterize the binding ability of -hydroxy-methylserine (Hms) with copper(II) and oxovanadium(IV) ions. The ligand was found to be generally a more efficient chelating agent than serine. Both of the deprotonated hydroxyl groups of Hms can be involved in coordination to vanadyl ions, whereas copper(II) binds in the same way as with serine.     

Stereoselective and Convenient Synthesis of Diethyl (E)-α-Triphenylstannyl or (Z)-α-Tributylstannyl α-Alkenylphosphonates

Diethyl (E)-α-triphenylstannyl or (Z)-α-tri-n-butylstannyl α-alkenylphosphonates are conveniently and stereoselectively prepared using a “tin-Peterson-like” reaction. Protonolysis of the carbon-tin bond of α-tributylstannyl derivatives proved to be easy and stereospecific.