Presence Of SnCl4 Research Articles

Synthesis of 3-sulfanylpropanols containing three consecutive stereocenters via tandem Michael–aldol reaction of enoylthioamides with acetals as key reaction

(2 S,3 S,1′ R)-2-(α-Methoxybenzyl)-3-phenyl-3-sulfanylpropionamides were diastereoselectively prepared by the reactions of N-cinnamoyl-4 S-isopropyl-5,5-dimethyloxazolidinethione with acetals in the presence of SnCl 4. The absolute configuration of the three newly created contiguous stereocenters was determined by the X-ray analysis of the disulfide. The amides were transformed into propanols by the reductive removal of the oxazolidinone moiety.

Polycyclic Furans from Condensations of Phenanthrene-9,10-quinone with Aryl Ethers and Phenol

Phenanthrene-9,10-quinone reacts with anisole in the presence of SnCl4.5H2O at 180 °C to give 11-methoxybenzo[b] phenanthro[9,10-d]furan and with veratrole to form both the 11,12-dimethoxy and the 10-monomethoxy analogues.

Reactions of 1‐Naphthols with π‐Acceptor p‐Benzoquinones: Oxidative Aryl Coupling vs. Non‐Oxidative Electrophilic Arylation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mechanistic studies on the formation of Pt(II) hydroformylation catalysts in imidazolium-based ionic liquids

The kinetics of the formation of the active species cis-[Pt II(PPh 3) 2Cl(SnCl 3)] and cis-[Pt II(PPh 3) 2(SnCl 3) 2] from the hydroformylation catalyst precursor cis-[Pt II(PPh 3) 2Cl 2] in the presence of SnCl 2, was studied in two different imidazolium-based ionic liquids. A large range of different chlorostannate melts consisting of 1-butyl-3-methyl-imidazolium cations and [Sn x Cl y ] (− y + 2 x) anions with varying molar fraction of SnCl 2, were prepared and characterized by 1H and 119Sn NMR. The observed chemical shifts point to major changes in the composition of the anionic species within the melt. The second ionic liquid employed, viz., 1-butyl-3-methyl-imidazolium-bis(trifluormethylsulfonyl)amide was prepared in a colorless quality that enabled its application in kinetic studies. The concentration and temperature dependence of the substitution of Cl − by [SnCl 3] − to yield cis-[Pt II(PPh 3) 2Cl(SnCl 3)], could be studied in detail. Theoretical (DFT) calculations were employed to model the reaction progress and to resolve the role of the ionic liquid in the activation of the catalyst. The available results are presented and a plausible mechanism for the formation of the catalytically active species is suggested.

A NEW APPROACH TO THE SYNTHESIS OF 4′-CARBON-SUBSTITUTED NUCLEOSIDES: DEVELOPMENT OF A HIGHLY ACTIVE ANTI-HIV AGENT 2′, 3′-DIDEHYDRO-3′-DEOXY-4′-ETHYNYLTHYMIDINE

Oxidation of 3′-O-TBDMS-4′,5′-unsaturated thymidine 3 with dimethyldioxirane (DMDO) allowed the isolation of the epoxide 4. Upon reacting with organosilicon reagents in the presence of SnCl4, 4 underwent stereoselective ring opening to give 4′-α-allyl (6), 4′-α-(2-bromoallyl) (7), 4′-α-(cyclopenten-3-yl) (8), and 4′-α-cyano (9) derivatives of thymidine. Reactions of the 3′-epimer 12 with organoaluminum reagents gave 4′-α-methyl (13), 4′-α-vinyl (14), and 4′-α-ethynyl (15) analogues. Compounds 13–15 were transformed into corresponding 2′,3′-didehydro-3′-deoxy derivatives. Evaluation of their ability to inhibit the replication of HIV in cell culture showed that 4′-ethynyl-d4T (19) is more potent and less toxic than the parent compound d4T.

Synthesis and Stability of New Nitrophenol Complexes of 99m Tc as Possible Hypoxia Imaging Radiopharmaceuticals

Seven new nitrophenol derivatives were synthesized; their 99mTc complexes (N2OS chelates), which are possible hypoxia tumor imaging agents, were prepared by the reaction with [99mTc]NaTcO4 in the presence of SnCl2 at pH 10. The in vitro biostabilty of the complexes was evaluated. The purity and stability (in human and rat serum) of the complexes were evaluated by chromatographic methods (TLC, HPLC). The most stable (for more than 6 h) is the complex of 99mTc with 3-[3′-N-(2″-hydroxy-5″-nitrobenzylamino)-2′-hydroxypropyl]-1-methylthiourea.

Synthesis and redox-active base-pairing properties of DNA incorporating mercapto C-nucleosides

Here, we describe the synthesis and incorporation of the nucleoside base analogue C-deoxyribonucleoside 3 carrying thiophenol into DNA. The 1′-β compound 3 was synthesized by Friedel–Crafts alkylation, followed by deprotection. The coupling reaction with 3,5-ditoluoyl-1-α/β-methoxy-2-deoxy- d-ribose and diphenyldisulfide in the presence of SnCl 4 afforded the α/β mixture 2 (β/α=2.8), and the β-form was separated by silica gel chromatography. After formation of the phosphoramidite derivative, the C-nucleoside 3 was incorporated into DNA. When the mercapto-bases were incorporated into complementary singled-stranded (ss) DNAs, the resulting duplex displayed high thermal stabilization on treatment with bubbling O 2 ( T m 73 °C), but was destabilized in the presence of mercaptoethanol ( T m 33 °C). CD spectra showed that the duplex had a right-handed double-stranded structure. Imino proton NMR studies of temperature stability suggested that the strength of hydrogen bonding around the mercapto C-nucleoside was larger when treated with bubbling O 2 than when in treated with reducing agent. Thus, formation of the base-to-base disulfide bond increased the stability of the duplex; correspondingly, reduction of the disulfide to two thiol bases destabilized the DNA reversibly. The duplex-forming disulfide base pair showed resistance to exonulease III . The present strategy could be used to introduce new functionalities into cells and novel biomaterials.

Reactions of 1-Naphthols with .PI.-Acceptor p-Benzoquinones: Oxidative Aryl Coupling vs. Non-Oxidative Electrophilic Arylation

We investigated the reactions of various 1-naphthols (NPOHs; 1) with p-benzoquinones (Qs), such as 1,4-benzoquinone (BQ) and p-chloranil (CA), as pi-electron acceptors. With electron-rich NPOHs 1a-c, oxidative biaryl coupling and subsequent dehydrogenation reaction took place selectively to give the corresponding 2,2'-binapthyl-1,1'-quinones 3a-c in excellent yield. In the case of electron-deficient NPOHs 1e, f, two different types of reactions occurred in the presence of SnCl4 and ZrO2 under similar conditions: SnCl4 mediated oxidative dimerization and trimerization of NPOH, while ZrO2 promoted electrophilic arylation of Qs with NPOH. The resulting products 3 would be useful synthetic intermediates for naturally occurring diosindigo B, biramentaceone and violet-quinone.

Synthesis and Anti‐HIV Activity of 4′‐Cyano‐2′,3′‐didehydro‐3′‐deoxythymidine

A new anti‐HIV agent 4′‐cyano‐2′,3′‐didehydro‐3′‐deoxythymidine (9) was synthesized by allylic substitution of the 3′,4′‐unsaturated nucleoside 14, having a leaving group at the 2′‐position, with cyanotrimethylsilane in the presence of SnCl4. Evaluation of the anti‐HIV activity of 9 showed that this compound is much less potent than the recently reported 2′,3′‐didehydro‐3′‐deoxy‐4′‐(ethynyl)thymidine (1).

Synthesis and Characterization of a Novel, Water‐Soluble Polymer with Pendant Groups Carrying cis‐Platinum Complex

The synthesis and characterization of a polymer with pendant groups carrying a cis‐platinum complex by the chemical modification route is discussed. Diethyloxomalonate functionalized polystyrene (DPS) is synthesized by the Friedel–Crafts acylation of polystyrene with diethyloxomalonate in the presence of SnCl4, by a batch‐wise addition process. The reaction of DPS with cis‐diaquo(trans‐1,2‐diaminocyclohexane)platinum(II) results in the formation of a cis‐platinum chelated polymer (PtDPS). Proton NMR and IR spectroscopies are used to confirm the transformation. The polymer synthesized is further characterized using thermogravimetric analysis (TGA) as well as UV and fluorescence spectroscopic techniques. PtDPS thus synthesized is further modified into a water‐soluble polymer by another polymer modification reaction resulting in the introduction of thiobarbituric acid moieties.

SnCl4‐Promoted Ethenylation Reaction of Hydroxylated Heteroarenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and anti‐HIV Activity of 4′‐Cyano‐2′,3′‐didehydro‐3′‐deoxythymidine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Double Nucleophilic Addition of Azide and Tetraallyltin to the Latent α,β-Unsaturated Aldehydes Using in situ Hydrolysis of the Imino Functionality Promoted by Tin(IV) Chloride Pentahydrate

In the presence of SnCl 4 .5H 2 O and acetic acid, a mixture of trimethylsilyl azide and tetraallyltin underwent 1,4- and subsequently 1,2-addition, respectively, with the α,β-unsaturated aldimines to give 1,3-hydroxy azides in good yields, where the hydrolysis of the intermediary imino species was found to be crucial.

SnCl4-Promoted Ethenylation Reaction of Hydroxylated Heteroarenes

Reaction of hydroxylated heteroarenes and acetylene in the presence of SnCl 4 and Bu 3 N (or Et 3 N) gives the corresponding ethenylated arenes. The reaction takes place at the neighboring position of the hydroxy group, andis applicable to quinolines, an isoquinoline, pyridines, and N-trifluoromethanesulfonylated indoles provided that the optimized conditions for the ethenylation and workup are employed.

Facile Double Nucleophilic Addition of Thiols and Tetraallyltin to Latent 2‐Alkynals Using in situ Hydrolysis of the Imino Functionality Promoted by Tin(IV) Chloride Pentahydrate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Potential Antimicrobial Agents: Trifluoromethyl‐10H‐phenothiazines and Ribofuranosides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Influence of stannous chloride on the adhesive properties of Corynebacterium diphtheriae strains

Stannous ion, as a chloride salt, influenced on the survival and adhesive properties of two toxigenic Corynebacterium diphtheriae of the sucrose-fermenting (241 strain) and non-sucrose-fermenting (CDC-E8392 strain) biotypes. Differences in survival fractions suggested differences in susceptibility of strains to bactericidal effect of stannous chloride (SnCl2). A number of 0.3% bacterial cells of 241 strain and 0.02% of CDC-E8392 strain survived after 220 micro l ml(-1) SnCl2 treatment. Results of polystyrene and spontaneous autoaggregation tests showed an increase in hydrophobicity of SnCl2 treated-bacteria. Spontaneous bacterial autoaggregation was induced in the presence of SnCl2. Stannous chloride also induced adherence to glass and totally inhibited the haemagglutinating activity of the non-sucrose-fermenting CDC-E8392 strain (original titer 32). Decrease in haemagglutination was dependent on SnCl2 concentration used. The presence of SnCl2 exerted differences in the expression of diphtheria bacilli surface carbohydrates possibly related with differences in degrees of haemagglutination and adherence to glass. Lectin-binding assays showed increase in the expression of cell surface receptors to the lectin Canavalia ensiformis (Con A) with affinity for mannose-like residues. The occurrence of cell filamentation suggests genotoxicity of SnCl2 to diphtheria bacilli. SnCl2 treatment was capable of modifying cell morphology, hydrophobins and adhesin expression, suggesting ability of C. diphtheriae to withstand oxidative stressing environment. Therefore, the SnCl2, widely used in nuclear medicine as reducing agent in the 99mTc-labelling process, may influence the outcome of bacterial infections.

Reaction of Selenostannanes with 1-Alkynes in the Presence of SnCl4

(Organylseleno)triethylstannanes RSeSnEt3 (R = Me, Ph) react with 1-hexyne and phenylacetylene in the presence of SnCl4 to give 1,2-bis(organylseleno)-1-organylethenes.

Domino Carbocationic Rearrangement of Aryl‐2‐(1‐N‐methyl/benzyl‐3‐indolyl)cyclopropyl Ketones: A Serendipitous Route to 1H‐Cyclopenta[c]carbazole Framework.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis, radio‐LC–MS analysis and biodistribution in mice of 99mTc–NIM–BAT

AbstractS,S′‐bis‐trityl‐N‐BOC‐1,2‐ethylenedicysteamine (S,S′‐bis‐trityl‐N‐BOC–BAT) was conjugated to 2‐nitroimidazole (NIM) through a propylene spacer in order to provide a precursor for a potential technetium‐99 m labelled hypoxia tracer. For labelling with technetium‐99 m, a two‐step one‐pot procedure was developed consisting of deprotection of the ligand by heating in mild acidic conditions and subsequent exchange labelling in the presence of SnCl2, tartrate and 99mTcO.The labelling reaction mixture was analyzed using electrospray radio‐LC–MS and the observed mass spectrum corresponding to the main radiometric peak was in accordance with the predicted structure of oxo–Tc(V)–NIM–BAT.99mTc–NIM–BAT was purified using RP–HPLC and its biodistribution was evaluated in normal mice at 10 min and 4 h p.i. 99mTc–NIM–BAT was cleared from plasma mainly by hepatobiliary excretion. Copyright © 2003 John Wiley & Sons, Ltd.