联二烯丁基硫醚衍生物合成呋喃的反应

本文报道以联二烯丁基硫醚为起始物的呋喃衍生物的合成方法.实验结果表明,β-联二烯丁基硫醚醇在氢化钠的作用下以很高的收率环化生成一个苯硫基离去的呋喃产物,β-联二烯丁基硫醚醛与外加亲核试剂作用后能得到多一个取代的类似呋喃产物,而β-联二烯丁基硫醚酮在P2O5的促进下也能环化生成呋喃衍生物.     

二价钌催化的金属卡宾经由的硫叶立德[2,3]-σ重排反应研究

报道烯(炔)基硫醚与α-重氮羰基化合物, 在[RuCl₂(p-cymene)]₂催化下, 经由金属卡宾发生硫叶立德[2,3]-σ重排反应(Doyle-Kirmse反应). 在Ru(II)作用下, α-重氮羰基化合物与烯丙基硫醚的反应以较好收率生成相应的[2,3]-σ重排产物高烯丙基硫醚. 同样条件下与炔丙基硫醚的反应则生成[2,3]-σ重排产物联烯和呋喃衍生物, 后者是联烯进一步在Ru(II)作用下重排的产物.     

Positional selectivity in electrophilic substitution reactions of π-excessive heterocycles (review)

Existing experimental data on positional selectivity in electrophilic substitution reactions of π-excessive heterocycles are classified. These data are discussed basing on the results of the authors' quantum-chemical calculations [RHF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d)] of the σ-complexes formed during attack of electrophiles such as H⁺, Me⁺, Me₃Si⁺, Br⁺, NO₂ ⁺, MeCO⁺, and SO₃ at the α- and β-positions of furan, thiophene, selenophene, pyrrole and its N-substituted derivatives, N-R-pyrroles (R = Me, t-Bu, SiMe₃, Si(i-Pr)₃, C₆H₄(p-NO₂), SO₂Ph, CHO, CO₂Me), and the corresponding α- and β-substituted electrophilic substitution products. The differences in energies of the α-and β-isomers of the σ-complexes characterize the preferred direction of electrophilic attack, while the differences in the energies of the isomeric products make it possible to assess the energy preference of one of them. Analysis of the obtained data demonstrates the effects of the studied heterocycles' structure, the nature of the electrophile, and the thermal and steric factors on the positional selectivity (α/β ratio) in electrophilic substitution reactions of π-excessive five-membered heteroaromatic compounds.     

S-ArylN,N-dialkylamidothiosulfates, a novel class of sulfenic acid derivatives

A method for the synthesis ofS-arylN,N-dialkylamidothiosulfates, a novel class of sulfenic acid derivatives, was proposed. The method is based on the reaction of arenesulfenyl chlorides withN,N-dialkylamidosulfinic acids or with secondary amines in liquid SO₂ in the presence of triethylamine. In the presence of halogen-containing Lewis acids,S-arylN,N-dialkyl-amidothiosulfates add to the C=C bonds to give aryl β-haloalkyl sulfides. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1484–1487, August, 2000.     

Reactions of azirines with sulfur nucleophiles. 4. Treatment of 2H-azirine with mercaptosubstituted acids. reactions of aziridinyl alkyl sulfides with carboxylic acids and acyl chloride derivatives

Treatment of 2H-azirines with mercaptosubstituted acids and their derivatives leads to -ketoamides and 2-aziridinyl alkyl sulfides, respectively. 2-Aziridinyl alkyl sulfides, in turn, react with carboxylic acids to give -ketoamides and substituted ethanethiol derivatives. Acylation of 2-aziridinyl alkyl sulfides with acyl halides generates a variety of products, depending on the reaction conditions; either products derived from cleavage and isomerization of the aziridinyl ring or (1-acylaziridinyl-2) alkyl sulfides are obtained.For communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 206–211, February, 1986.     

Synthesis of β-nitroxyalkylnitramines

β-Nitroxyalkylnitramines were obtained by nitration of β-hydroxyalkyl sulfamates, products of the condensation of derivatives of sulfamic acid with alkene oxides, by a mixture of HNO₃ and H₂SO₄. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1061–1062, May, 1997.     

Regioselective alkanoylation of cyclodextrins

The regioselective transesterification of native α- and β-Cyclodextrins (CDs) with vinyl acetate and vinyl laurate is presented in this paper. The reactions were carried out in dimethyl sulfoxide by using low molecular weight salts (Na₂HPO₄ and NaCl, respectively). MALDI-TOF mass spectrometry and NMR analysis were applied to investigate the chemical structure and the degree of the modification of the final products. Results show that these salts catalyze regioselective transesterification between β-CDs and vinyl laurate aiming for the secondary C-2 hydroxyl group. The synthesis and separation of β-CD-laurate derivatives leads to a mixture of mono-2-O-dodecanoyl-β-CD and native β-CDs. Unreacted β-CDs could be selectively removed enzymatically by cyclodextrin glucosyl-transferase (CGTase) and β-amylase.     

Gold‐Catalyzed Cyclization of Furan‐Ynes bearing a Propargyl Carbonate Group: Intramolecular Diels–Alder Reaction with In Situ Generated Allenes

Gold‐catalyzed cyclization of various furan‐ynes with a propargyl carbonate or ester moiety results in the formation of a series of polycyclic aromatic ring systems. The reactions can be rationalized through a tandem gold‐catalyzed 3,3‐rearrangement of the propargyl carboxylate moiety in furan‐yne substrates to form an allenic intermediate, which is followed by an intramolecular Diels–Alder reaction of furan and subsequent ring‐opening of the oxa‐bridged cycloadduct. It was found that the steric and electronic properties of phosphine ligands on the gold catalyst had a significant impact on the reaction outcome. In the case of 1,5‐furan‐yne, the cleavage of the oxa‐bridge in the cycloadduct with concomitant 1,2‐migration of the R¹ group occurs to furnish anthracen‐1(2H)‐ones bearing a quaternary carbon center. For 1,4‐furan‐yne, a facile aromatization of the cycloadduct takes place to give 9‐oxygenated anthracene derivatives.     

Allenes—XXXV : The addition of allenic carbenes to oxygen heterocycles

Dimethylvinylidene carbene from 1-bromo-3-methylbutadiene and potassium t-butoxide adds to 2,5-dihydrofuran and 2,3-dihydropyran to give the corresponding allenic cyclopropanes. 1,4-Cycloaddition of the allenic carbene to furan followed by hydration during work up yields the bicyclic ketone 11.     

Enhancement of aqueous solubility of tricyclic acyclovir derivatives by their complexation with hydroxypropyl-β-cyclodextrin

Solubilities of tricyclic acyclovir derivatives in buffered aqueous solutions of hydroxypropyl-β-cyclodextrin (HP-β-CD) at pH 5.5 and 7.0 were determined at 25 and 37 °C. Complexation of these compounds with HP-β-CD resulted in a noticeable increase of their solubility; nevertheless it was limited to tricyclic derivatives of acyclovir carrying an aryl substituent. Combination of ¹H NMR and DSC techniques demonstrated the existence of inclusion complexes between acyclovir derivatives and HP-β-CD. The stability constants, estimated using the Higuchi–Connors method, were found in the range of 10–100 M⁻¹. Additionally, the pK _a values at 25 °C and molar extinction coefficients in aqueous buffered solutions were also determined for all studied compounds.     

Acid-mediated cyclotransformations of 4a-substituted 4H-4a,5-dihydroindeno[1,2-<Emphasis Type="Italic">b</Emphasis>]pyridines as a new route to 9a-substituted 1H-fluorenes

4a-Substituted dihydroindenopyridines undergo cleavage of the C_(9b)=N bond in water-containing acidic medium, resulting in the formation of diastereomeric ethyl α-acetyl-β-(2,3-dihydro-1,3-dioxo-1H-inden-2-yl)-β-phenylpropionates and 9a-substituted 1,9a-dihydrofluore-none derivatives. The cyclization of α-acetyl-β-(2,3-dihydro-1,3-dioxo-1H-inden-2-yl)-β-phenyl-propionates with benzylammonium acetate affords 3-benzylamino-1,9a-dihydrofluorenones. The methanobenzo[a]azulene compound is also found among cyclization products. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii. No. 2, pp. 249–258, February, 2007.     

Electrophilic cyclization of α- and β-geranyl acetates by mercury(II) trifluoroacetate

Electrophilic cyclization of β-geranyl acetate promoted by mercury(II) trifluoroacetate leads to mixtures of α- and γ-5αH-cyclogeranyl acetate derivatives and 6α-hydroxy-5αH-and 6α-hydroxy-5βH-cyclogeranyl acetate derivatives mercurated at the C-3 atom. The ratio of the unsaturated and hydroxymercurated products depends on the reaction conditions. α-Geranyl acetate reacts with mercury(II) trifluoroacetate to give a mixture of 6α-hydroxy-5αH-and 6α-hydroxy-5βH-geranyl acetates, mercurated at C-9, with an equatorial mercurated methylene group at C-4. The mercury-containing groups in mercurated cyclogeranyl derivatives can easily be reduced or replaced by an oxygen-containing functional group; this constitutes a convenient route to polyfunctional cyclogeranyl derivatives that are difficult to obtain. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 1997.     

Diaminomethylidene derivatives of β-oxo sulfones as potential reagents in heterocyclic synthesis and chelating ligands

Active methylene β-oxo sulfones add to the C≡N bond of benzoylcyanamide in the presence of catalytic amounts of Ni(acac)₂. Debenzoylation of the reaction products under the action of MeONa in MeOH gives N,N′-unsubstituted diaminomethylidene derivatives of β-oxo sulfones (acyl(R-sulfonyl)ketene aminals), which can be used as reagents for heterocyclic synthesis and as chelating ligands. The syntheses of 2-amino-3-arylsulfonylpyridin-4(1H)-ones and 5-sulfonylcytosine derivatives are presented as examples.     

Enantioselective Oxidation of Sulfides Catalyzed by Chiral MoV and CuII Complexes of Catechol-Appended β-Cyclodextrin Derivatives in Water

The two modified β-cyclodextrin (β-CD) derivatives having catechol-type ligand (2,3- and 3,4-dihydroxy groups on the benzoate ring) were synthesized. The chiral catalytic activity of their Mo^V and Cu^II complexes was examined in the asymmetric oxidation of aromatic sulfides using hydrogen peroxide in water (pH 6.0). The oxidation with the Mo^V complexes of two β-CD derivatives were more accelerated than that with the Cu^II complexes. The sign of the optical rotation of the sulfoxides obtained in the above two cases showed the opposite configuration in the oxidation of the same sulfide. The difference of the enantioselectivity appeared also between the two complexes of the 2,3- and 3,4-dihydroxybenzoate derivatives with the same metal ion. While the use of the Mo^V complexes with the catechol derivatives yielded the sulfoxides with 35–65% ee, the use of the Cu^II complexes gave the products with the␣opposite configuration at 26–52% ee. The chiral induction in the oxidation, observed conversely between the␣catalysts, was reflected on the chiral conformation of the respective metal catalysts, showed in Induced Circular Dichroism (ICD) spectra. The highest optical yield, 65%, was observed in the oxidation of butyl phenyl sulfide using the catalytic amount (0.1 equiv) of the Mo^V complex with mono-6-O-(3,4-dihydroxybenzoyl)-β-CD. The reaction gave predominantly the (S)-sulfoxide in 95% chemical yield.     

An Efficient Approach to Regio- and Stereodefined Fully-Substituted Alkenylsilanes by Pd-Catalyzed Allenic C(sp3)−H Oxidation

A highly efficient palladium-catalyzed functionalization of allenylsilanes to give regio- and stereodefined fully-substituted alkenylsilanes has been developed. This oxidative coupling reaction showed good functional group compatibility with exclusive regio- and stereoselectivity. The pending olefin on the silyl group was shown to be an indispensable element for the initial allenic C(sp³)−H bond cleavage, and performs as the directing group to control the overall selectivity. The addition of substoichiometric amounts of Et₃N was found to increase the reaction rate leading to a higher reaction yield. The reaction can be easily scaled up and applied for the late-stage functionalization of natural products and pharmaceutical compounds, including amino acids and steroid derivatives. The newly introduced functional groups include aryl, alkynyl, and boryl groups. The highly strained four-membered ring, silacyclobutene was obtained when B₂pin₂ was employed as the coupling partner. Mechanistic studies, including kinetic isotope effects, showed that the allenic C(sp³)−H bond cleavage is the rate-limiting step.     

Substituted Pyrrolo[3,4-<Emphasis Type="Italic">a</Emphasis>]carbazoles from Reactions between 3-(1-Methoxy-vinyl)indoles and Maleimides

Summary. 5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed into the hydroxy derivatives by treatment with H₂SO₄, selectively reduced to the ether by H₂/Pd–C, and in the imide moiety by L-Selectride^?. From the analogous BOC protected indole derivative the parent α,β-unsaturated ketones were obtained, which were transformed into hydroxyimino compounds, and which could be deprotected by heating to the melting point. Deprotection of the tosyl derivatives was not successful. The imide part of the molecule was hydrolyzed using methanolic NaOH. The stereochemistry of all products was elucidated mainly by spectroscopic methods, and compared with results of calculations.     

Substituted Pyrrolo[3,4-a]carbazoles from Reactions between 3-(1-Methoxy-vinyl)indoles and Maleimides

5-Methylenolether derivatives of pyrrolo[3,4-a]carbazoles were obtained from cycloadditions between 3-(1-methoxyvinyl)-1-tosylindole and N-substituted maleimides. They were transformed into the hydroxy derivatives by treatment with H₂SO₄, selectively reduced to the ether by H₂/Pd–C, and in the imide moiety by L-Selectride^?. From the analogous BOC protected indole derivative the parent α,β-unsaturated ketones were obtained, which were transformed into hydroxyimino compounds, and which could be deprotected by heating to the melting point. Deprotection of the tosyl derivatives was not successful. The imide part of the molecule was hydrolyzed using methanolic NaOH. The stereochemistry of all products was elucidated mainly by spectroscopic methods, and compared with results of calculations.     

N-Alkylated Derivatives of 1,5-Dideoxy-1,5-iminoxylitol as β-Xylosidaseand β-Glucosidase Inhibitors

Summary.  A range of lipophilic derivatives of the D-xylosidase inhibitor 1,5-dideoxy-1,5-iminoxylitol was synthesized by N-alkylation of the parent compound with different alkyl halides. Inhibitory activities of the products obtained were measured with β-glucosidase from Agrobacterium sp., a family 1 enzyme, as well as with β-xylosidase from Thermoanaerobacterium saccharolyticum belonging to family 39 of the glycohydrolases. Whereas the former enzyme, which has low β-xylosidase activity, was only moderately inhibited, with K _i values in the millimolar range, good inhibition was observed with the latter one. Inhibitors with terminally functionalized N-alkyl chains open up opportunities for novel applications as affinity ligands as well as for various types of tagging for diagnostic purposes. Received October 25, 2001. Accepted November 19, 2001     

Reduction of 2,3-<Emphasis Type="Italic">Seco</Emphasis>-28-oxo-19<Emphasis Type="Italic">β</Emphasis>,28-epoxy-18<Emphasis Type="Italic">α</Emphasis>-olean-2,3-dicarboxylic acid and its cyclic anhydride

Reduced derivatives of 2,3-seco-28-oxo-19β,28-epoxy-18α-olean-2,3-dicarboxylic acid and its cyclic anhydride were prepared. Reduction of the starting 2,3-secodicarboxylic acid by NaBH₄–I₂ produced the 2,3-seco-2,3-dihydroxy derivative. Reaction of the starting anhydride with LiAlH₄ gave the 2,3-seco2,3,19β,28-tetrahydroxy derivative. Cyclization using acidic reagents of the 2,3-seco-2,3-hydroxy- and 2,3seco-2,3,19β,28-tetrahydroxy derivatives gave the corresponding cyclic ethers containing an oxepane ring. The anhydride ring was reduced by NaBH₄ to the corresponding ε-lactone, the structure of which was confirmed by an x-ray crystal structure.     

Electron transfer and subsequent reactions during electrochemical oxidation of aryl- and alkylthio derivatives of mucochloric acid

The electrochemical oxidation of aryl- and alkylthio derivatives of mucochloric acid (3,4-dichloro-5-hydroxyfuran-2(5H)-one) in MeCN-Bu₄NBF₄ (0.1 mol L⁻¹) was investigated. It was shown that all sulfides are electrochemically active, from one to five oxidation steps of sulfur-containing groups were observed for them. The ease and direction of oxidation of the thio group depend on its nature and position in the furanone ring. 3-Substituted 2(5H)-furanones possess the lowest oxidation potential. 4-Substituted 2(5H)-furanones are predominantly oxidized to sulfoxides, 5-aryl- and -alkylthio derivatives undergo fragmentation to give mucochloric acid, and 3-arylthio derivative gives complex unidentified mixture of products. In the case of 3,4-bis(4-methylphenylthio) derivative, the oxidation product of the arylthio group at the 3 position to the corresponding sulfoxide was isolated. Based on the data from cyclic voltammetry with different concentrations of a substrate and water added, the results of preparative electrolysis and quantum chemical calculations, possible mechanisms of electrochemical oxidation of mucochloric acid-derived sulfides are discussed. The initial common step is a reversible single-electron transfer from the substrate molecule to form highly reactive radical cation.