Regioselective synthesis of vinylic derivatives of common monosccarides through their activated stannylene acetal intermediates

The regioselective C-2-O-acrylation and metacrylation of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside and methyl 4,6-O-benzylidene-alpha-D-galactopyranoside through their corresponding organotin intermediates have been studied. Regioselectivity was achieved through the formation of a tin chelate of the 2,3-diols. Thus, methyl 4,6-O-benzylidene-alpha-D-glucopyranoside and methyl 4,6-O-benzylidene-alpha-D-galactopyranoside were reacted with dibutylstannylene to give the corresponding dibutylstannylene acetal intermediates that were then reacted in a regioselective manner with acryloyl chloride or metacryloyl chloride in the presence of triethylamine (TEA) or pyridine to give the vinylic type monomeric compounds. The monomeric products containing glucose and galactose units from each reaction were separated by column chromatography using a gradient of n-hexane and ethyl acetate as eluant. The structure of the obtained compounds were confirmed using (1)H-, (13)C- and 2D NMR spectroscopy.     

Benzopyranopyridine derivatives 3. Reaction of 1-azaxanthone with grignard reagents

Three different classes of compounds were isolated in the reaction of Grignard reagents with 5-H[1]benzopyrano[2,3-b]pyridin-5-one, commonly called 1-azaxanthone. The formation of (a) 4-substituted 1,4-dihydro-1-azaxanthones (II), (b) 5-substituted-5-hydroxy-1-azaxanthenes (III) or (c) 4,5-disubstituted-1-azaxanthenes (IV) is dependent on the solvent used in the preparation of the Griganrd reagent (i.e. ether or tetrahydrofuran), the steric properties of the reagent and on the temperature. The isolated compounds were characterized by chemical derivatives and/or spectroscopic analyses.     

Some perfluoroalkyl grignard reagents and their derivatives

Some perfluoroalkyl Grignard reagents have been prepared in high yields through halogen-metal exchange reactions between perfluoroalkyl iodides (R_fI) and EtMgBr. Derivatization with Me₃SiCl gave satisfactory yields of the corresponding silylated products in THF. However, ether was a very poor solvent for reaction of R_fMgBr with these chlorosilanes. The exchange reaction between R_fI and EtMgBr was nearly quantitative in ether as evidenced by high yields of the 1-hydroperfluoroalkanes upon hydrolysis, but the major production from the attempted silylation in ether was a trans- vinyl bromide [1], i. e.

Spectral data are presented for several new compounds.     

Synthesis of arylrhenium derivatives using organocopper reagents

Aryl derivatives (η-C₅H₅)Re(NO)(CO)R (R = C₆H₅, o-, m-, or p-tolyl, m- or p-trifluoromethylphenyl) have been conveniently prepared in 80–92% yields from (η-C₅H₅)Re(NO)(CO)Cl using an excess of the arylcopper reagents RCu. Reactions of (η-C₅H₅)Re(NO)(CO)X (X = Cl, Br, I) with phenylmagnesium bromide or phenyllithium afford the phenylrhenium compound in low yield or not at all, and an explanation is offered for this. Optimum reaction conditions, sources of the arylcopper reagent, and other variables in the syntheses have been explored.     

Some derivatives of rhodanine as analytical reagents

Twenty-two derivatives of rhodanine were investigated as potential spectrophotometric and spot test reagents. Sensitive reactions for silver, gold, copper(I), mercury(II), palladium and some other metals are described. None of the reagents is suitable for spectrophotometry ; all but one produce non-extractable, colloidal, metal-ion complexes. The introduction of a sulphonic acid group into the molecule, however, makes the complexes water-soluble.     

Titanocene and zirconocene dichloride derivatives with hydroxylic reagents

The reaction of Cp₂TiCl₂ (Cp = C₅H₅) with ethanol in the presence of Et₃N in acetonitrile yields the derivatives CpTiCl(OEt)₂ or CpTiCl₂(OEt). Similar reactions of Cp₂MCl₂ (M = Ti or Zr) with glycols (GH₂ = 1,2-propanediol, 2,3-butanediol, pinacol or hexylene glycol) or fluoro-β-diketones (KeH = hexafluoroacetylacetone(hfa), benzoyltrifluoroacetone (bta) or 2-thenoyltrifluoroacetone (tta)) gave CpMCl(G) or CpMCl(Ke)₂.     

9-Imino derivatives of dihydroxyanthraquinones as analytical reagents

The synthesis, characteristics, properties and reactions with metallic ions of the reagents isticin-9-imine, alizarin-9-imine and 3-sulphoalizarin-9-imine have been studied.     

Alkylation of carboxylic acid derivatives with dialkoxytitanacyclopropane reagents

Methods for the generation of dialkoxytitanacyclopropanes (dialkoxytitanium olefin complexes) are surveyed. Alkylation of carboxylic acid derivatives with these reagents giving rise to -titanio ketones and related species, which are spontaneously transformed into the corresponding cyclopropane compounds or react with external electrophiles, are considered.     

Donor-substituted diphenylacetylene derivatives act as electron donors and acceptors

Despite the predominant electron donor character of p-phenylenediamine, our studies on extended p-phenylenediamine derivatives show that they can not only be chemically oxidized, giving well-known Wurster-type radical cations, but also be chemically reduced, giving radical anions. Making use of EPR/ENDOR spectroscopy and supported by DFT calculations, we were able to reveal the extent of π-electron delocalization in the paramagnetic species and to shed light onto the geometry and bond lengths. While for the radical anions spin was found to be mostly delocalized into the π-system, the radical cations can be described as essentially N-centered. Furthermore, we performed electrochemical characterizations using cyclic voltammetry to gain insight into the thermodynamics of the redox processes. The photophysical properties of the parent extended p-phenylenediamine were investigated by absorption, emission, and excitation spectroscopy. The fluorescence quantum yield and the excited-state lifetime of the neutral precursors in hexane and acetonitrile were determined to establish elementary differences originating from solvent effects.     

New routes to beta-cycloalkylalanine derivatives using serine-derived organozinc reagents

Two distinct routes to beta-cycloalkylalanine derivatives have been developed. The first route employs the reaction of the iodoalanine-derived zinc-copper reagent 2 with cycloalk-1-en-3-yl phosphates, and the second uses the palladium-catalysed coupling of the iodoalanine-derived zinc reagent 1 with cycloalkenyl triflates; in each case, catalytic hydrogenation of the unsaturated product leads to the protected beta-cycloalkylalanine. The latter route allows access to a range of cycloalkyl derivatives, with ring sizes of 5-8. beta-(1-Methyl-1-cyclohexyl)alanine may be prepared using reaction of the zinc-copper reagent 2 with 3-methyl-2-cyclohexenyl chloride, followed by hydrogenation. The corresponding cyclopentyl derivative may be prepared by reaction of the same zinc-copper reagent 2 with diethyl geranylphosphate, followed by ring-closing metathesis and hydrogenation.     

Reactions ofN-methoxydiazen-N′-oxidoacetic acid derivatives with electrophilic reagents

Bromination, methylation, and nitration ofN-methoxydiazen-N′-oxidoacetic acid derivatives were investigated. The results of the reactions depended significantly on both the type of the starting compound and the electrophilic reagent.     

Highly ortho-selective cross-coupling of dichlorobenzene derivatives with Grignard reagents

Highly ortho-selective cross-coupling of dichlorobenzene derivatives with Grignard reagents was realized using a combination of Pd2(dba)3 and PCy3. Use of hydroxylated terphenylphosphines further improved the reactions of dichlorophenol and dichloroaniline.     

Protolytic properties of some reagents: H-acid azo derivatives

The quantitative characteristics of protolytic processes in systems of H-resorcinol, beryllon III, and H-aminophenol reagents were determined by potentiometric titration graphically and using calculations. Diagrams were built of the speciation of these reagents in the pH range 2–13 and of the distribution of their mole fractions in the solution at given pHs. The existence of the azo-hydrazone tautomeric equilibrium was demonstrated for the H₂R^3? species of H-resorcinol.     

Reaction of O-acyl derivatives of polynitroalkanes with electrophilic reagents

Conclusions The O-acyl derivatives of polynitroalkanes (trinitromethane, dinitromethane and 1,1-dinitroethane) react with various electrophilic reagents to give the corresponding trinitro- and dinitromethyl derivatives.Translated from Izvestiya Akademiya Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 344–350, February, 1973.     

Asymmetric derivatives of carbohydrazide and thiocarbohydrazide as analytical reagents

The synthesis and analytical properties of two asymmetric derivatives of carbohydrazide and thiocarbohydrazide with pyridine and phenol have been studied. The compounds tested are 1-(2-pyridylmethylideneamino)-3-(salicylideneamino)urea and 1-(2-pyridylmethylideneamino)-3-(salicylideneamino) thiourea. The analytical utility of these reagents is outlined. A spectrophotometric method for determining the formation constants of the complexes is described.     

Efficient palladium-catalyzed nucleophilic addition of triorganoindium reagents to carbocyclic derivatives

Palladium (0)-catalyzed allylic substitution reactions employing triorganoindium reagents have been investigated. In situ generated vinyl- and arylindiums react with substituted and unsubstituted cyclohex-2-enyl esters in the presence of 1-3 mol % Pd(2)(dba)(3) to produce vinyl- or arylcyclohexenes in moderate to excellent yields. The stereoselectivity of this process was also examined, and evidence is presented that the reaction proceeds with inversion of stereochemical configuration.     

New stable reagents for the nucleophilic trifluoromethylation. 1. Trifluoromethylation Of carbonyl compounds with N-formylmorpholine derivatives

A new stable equivalent of the trifluoromethyl anion has been synthesized from fluoroform. It reacts with nonenolizable carbonyl compounds such as the Ruppert's reagent.