A novel synthesis of 2'-hydroxy-1',3'-xylyl crown ethers

Six novel 2' - hydroxy - 1',3' - xylyl crown ethers (8a–e and 13)¹ have been synthesized utilizing the allyl group to protect the OH function during the cyclization reaction. The macrocycles 6a-e were formed in yields of 26 to 52%, by intermolecular reaction of 4 - chloro - 2,6 - bis(bromomethyl) - 1 - (2 - propenyloxy)benzene (5) with polyethylene glycols; 6a was also obtained by an intramolecular cyclization reaction of monotosylate 14.A 30-membered ring with a 2' - hydroxy - 1',3' - xylyl sub-unit was obtained in 87% yield by reaction of ditosylate 9 with bis [2 - (o - hydroxyphenoxy)ethyl]ether (11) in the presence of cesium fluoride. The synthesis of crown ethers with a 2' - hydroxy - 1',3' - xylyl sub-unit (1c–e, H for CH₃) by demethylation of the corresponding 2'-methoxy crown ethers 1c–e with lithium iodide were unsuccessful; it would appear that the demethylation reaction is restricted to 15- and 18-membered rings. One of the 2' - hydroxy - 1',3' - xylyl crown ethers 8d forms a crystalline 1:1-complex with water.     

2'-Desoxytubercidin: synthese des o-3'-phosphoramidites und kondensation zu 2'-desoxytubercidylyl(3' → 5')-2'-desoxytubercidin

The phosphoramidite of 2'-deoxytubercidin (2) has been prepared by phosphitylation of compound 3b with chlorodiisopropylaminomethoxyphosphane. The intermediate 3b was obtained from 2'-deoxytubercidin (1) by N⁴-benzoylation and subsequent O-5'-dimethoxytritylation. Condensation of compound 2 with O-3'-silylated 3e gave the fully protected dimer 4b, which was converted into 2'-deoxytubercidylyl (3' → 5')-2'-deoxytubercidin(4a). Compound 4a isoster with 2'-deoxyadenosylyl(3' → 5')-2'-deoxyadenosine (d(ApA)) exhibits a hypochromicity of 11% (270 nm) due to strong stacking interactions. Cleavage of the dinucleoside monophosphate 4a with nuclease S₁ occurs five times faster than that of d(ApA). This shows that the single strand specific enzyme recognises the geometry of the stacked nucleobases.     

Regarding the structure of [2.2](2,6,2',7')-naphthalenophane-1,11-diene and its conformational mobility

The synthesis of [2.2](2,6,2',7')naphthalenophane -1,11 - diene 4 has been effected by pyrolysis of the bis-sulphoxide 10, in turn prepared by a ring-contraction procedure of the [3.3]dithiacyclophane 7. The diene 4 has been fully characterized by spectroscopic and chemical methods. The variable-temperature ¹H NMR spectra of the diene 4 indicated that the compound undergoes conformational flipping in solution and has a conformational energy barrier ΔG^≠_25°. 14.9 kcal mol^-1 and a coalescence temperature T_c 38° for the internal protons H_c and H_c' (at 100 MHz). These results differ from those previously recorded. A complete assignment of the pmr spectrum of the cyclophane diene 4 at 270 MHz is presented together with the spectrum of the corresponding saturated [2.2]cyclophane 3.     

Synthese de la cyclo-5'-8 desoxy-5' adenosine: stereochimie et mecanisme de la cyclisation d'un derive de l'iodo-5' adenosine par le zinc

N,N'-Dibenzoyl 2', 3'-O-isopropylidene 5'-deoxy 5'-iodo adenosine can efficiently transformed into the corresponding 5',8-cyclo-7,8-dihydronucleoside by zinc in pyridine. Only one diastereoisomer is obtained. By spin decoupling and NOE techniques at 250 MHz, the R-configuration at C-8 was established. This compound showed typical dihedral angles of about 90° for the vicinal protons H-1', H-2' and H-3', H-4'. Using adenosine derivatives stereospecifically labelled at C-5', it was demonstrated that the cyclisation occurs with racemisation at that position.     

Synthesis of licoflavone-a and 6',6'-dimethylpyrano(2',3':7,8)flavone

Licoflavone-A assigned structure of 6-C-prenyl-7,4'-dihydroxyflavone 5 has been synthesized by condensing 5-C-prenyl-2-hydroxy-4-prenyloxyacetophenone 2 with p-prenyloxybenzaldehyde in the presence of alkali. The resulting chalcone 3 on cyclodehydrogenation with DDQ gave 6-C-prenyl-7,4'-diprenyloxyflavone 4 which on boiling with aqueous morpholine afforded the natural product. This synthesis uses, for the first time, protection of phenolic hydroxyls by O-prenylation and DDQ for conversion of chalcone to flavone. 6',6'-Dimethylpyrano (2',3':7,8)navone 8 has been synthesized by the Hlubucek reaction of 7-hydroxyflavone 6 with 2-chloro-2-methyl-3-butyne.     

Die reaktion von 4-(α-hydroxyalkyliden)-Δ-5-isoxazolonen mit bifunktionellen stickstoffbasen

The 4-(α-hydroxyalkylidene)-Δ²-5-isoxazolones2 exist in the β-ketoenol form (“vinyloge car☐ylic acids”),2a,c react with guanidine and amidines to give only the enolates4, whereas they react both with hydrazines and 1,2-diamines to form the enamines6 and9 (“vinyloge amids”). The 4-(α-ethoxyalkylidene)-Δ²-5-isoxazolones 7 (“vinyloge esters”) condense with guanidine, benzamidine, and urea to affort the enamines8. Attempted ring-opening by bases failed whilst catalytic hydrogenation of the enamines6 and8 yielded the pyrazoles10,11 and diazepines12. The structures of the compounds have been elucidated by NMR and IR-spectra.     

Biphenylenes-xxxi: Condensation of benzocyclobutene-1,2-dione with aliphatic and heterocyclic 1,2-diamines and the synthesis of cis-2-cyano-3-(2'-cyanovinyl)-1,4-diaz

As possible routes to 1,4-diazabiphenylene and its 2,3-disubstituted derivatives we have studied the condensation of benzocyclobutene-1,2-dione (BBD) with various 1,2-diamines. Instead of giving the 1,4-diazabiphenylene ring system, BBD reacted with ethylenediamine, diaminomaleonitrile, 4,5-diaminopyrimidine, 2-aminopyridine, also 2,3- and 3,4-diaminopyridine to give, respectively, 2-o-carboxyphenylimidazolidinium acetate 4, 3,4-dicyano-2,5-dihydro[2,5]benzodiazocine-1,6-dione 10, 4-amino-5a,9b-dihydro-5-,9b-dihydroxybenzo [3',4']cyclobuta[1',2'-4,5]imidazo[1,2-c]pyrimidine 14, 5a,9b-dihydro-5a,9b-dihydroxybenzo[3',4']cyclobuta[1',2'-4,5] imidazo[1,2-a]pyridine 17, the 4-amino derivative 16 of the latter, and the zwitter ion 18 of 4-amino-3(2-carboxy-benzylideneamino) However, BBD reacted with 4,5-diaminobenzotriazole to give the expected 1,2,3,6,11-penta-aza-1-H-indeno [4,5-b]biphenylene 20, which, on amination followed by oxidation, gave a very low yield of cis-2-cyano-3-(2'-cyanovinyl)-1,4-diazabiphenylene 3. In model experiments, 7,8-diphenylfurazano [3,4-f]quinox-aline 28 was reduced to 2,3-diamino-5,6-diphenyl quinoxaline 29, which on oxidation, gave a mixture of cis- and trans-2-cyano-3-(2'-cyanovinyl)5,6-diphenylpyrazine, 30 and 31. The pentacyclic compounds, 1,3,6,II-tetra-aza-2-oxa-2H-indeno [4,5-b]biphenylene 23 and 1,3,5,10-tetra-aza-1-H-indeno[5,6-b] biphenylene 25, were formed from BBD and the appropriate 1,2-diamines but the 5-membered heterocyclic rings could not be cleaved by reduction and hydrolysis respectively) to give tetracyclic diamines which might have undergone oxidation to give derivatives of 1,4-diazabiphenylene. Compounds 14, 16, 20, 23, 25 and 28 are derivatives of new heterocyclic systems.     

Studies on the syntheses of heterocyclic compounds—DCCLXII : Alternative synthesis of trans-3-(1'R*-hydroxyethyl)-4-(2',2'-dimethoxyethyl)-2-azetidinone,a synthetic intermediate of thienamycin

Synthesis of trans-3-(1'R^*-hydroxyethyl)-4-(2',2'-dimethoxyethyl)-2-azetidinone (5), an important intermediate for the synthesis of thienamycin (1), was investigated starting from the isoxazoline derivatives 3 and 9. The most effective method was catalytic hydrogenation of trans-4-t-butoxycarbonyl-3-(2,2'-dimethoxyethyl)-5-methyl-isoxazoline (9) with Adams catalyst in acetic acid, followed by trimethylsilylation of the resulting epimeric aminoesters 11A and B, cyclization with EtMgBr, and deblocking. Novel reductions of the isoxazolines with sodium borohydride and nickel chloride or with diborane followed by catalytic hydrogenation were also reported.     

Synthesis,antimicrobial and anticancer activities of some new N-methylsulphonyl and N-benzenesulphonyl-3-indolyl heterocycles: 1st Cancer Update

A series of 1-(N-methyl 2a–c and N-benzenesulphonyl-1H-indol-3-yl)-3-aryl-prop-2-ene-1-ones 3a–c were prepared and allowed to react with urea, thiourea or guanidine and gave the pyrimidine derivatives 4a–c to 9a–c. Base catalyzed reaction of 2a–c or 3a–c with ethyl acetoacetate gave cyclohexanone derivatives 10a–c and 11a–c, respectively. Reaction of the latter compounds with hydrazine hydrate afforded indazole derivatives 12a–c and 13a–c, respectively. On the other hand, condensation of 2c or 3c with some hydrazine derivatives namely, hydrazine hydrate, acetyl hydrazine, phenyl hydrazine and benzyl hydrazine hydrochloride gave pyrazole derivatives 14a,b-17a,b, respectively. Moreover, reaction of 2c or 3c with hydroxyl amine hydrochloride gave isoxazole derivatives 18a,b. The newly synthesized compounds were tested for their antimicrobial activity and showed that, compounds 14a, 14b, 15a and 15b were found to be the most active ones of all the tested compounds toward Salmonella typhimurium (ATCC 14,028) compared to the reference drug chloramphenicol. Eighteen new compounds namely, pyrimidin-2(1H)-ones 4a–c and 5a–c, pyrimidin-2(1H)-thiones 6a–c and 7a–c and pyrimidin-2-amines 8a–c and 9a–c were tested for their in vitro cytotoxicity against human liver carcinoma (HEPG2), human breast cancer (MCF7) and human colon cancer (HCT-116) cell lines and showed that, compounds 4c, 5c, 6c, 8c and 9c were found to be the highly active compounds compared to the reference drug doxorubicin.     

The synthesis and crystal structure of 5-acetyl-2'-deoxyuridine

5- Acetyl - 2' - deoxyuridine (1) has been synthesised by treating 2' - deoxy - 5 - ethynyluridine with dilute sulphuric acid. Condensation of the trimethylsilyl derivative of 5-acetyluracil with 2-deox-3, 5-di-O-p-toluoyl-α-d-erythropen chloride gave a mixture of α- and β-anomeric blocked nucleosides from which the α-anomer was isolated and the p-toluoyl groups removed to give 5 - acetyl -1 - (α - d - 2- deoxyerythropentofuranosyl) uracil. Only a poor yield of the β-anomer (1) was obtained by this procedure. The UV spectra and m.p. obtained for 1 differed from the values quoted in the literature. The crystals of 1 are monoclinic, space group P2₁, with a = 9.525, b = 12.16, c = 5.22 Å, β = 92.03° and two molecules in the unit cell. The structure was refined by least-squares calculations to R 3.4% for 1426 observed counter amplitudes. The pyrimidine ring is essentially planar with the acetyl group inclined at 6° to it. The sugar ring has the highly unusual C(4')-exo conformation and the arrangement about C(4')-C(5') is such that O(5') is oriented gauche with respect to both O(1') and C(3'). The glycosidic torsion angle O(1')-C(1')-N(1)-C(6) is 56° (anti conformation).     

Chemo-, stereo- and regioselective hydrogenolysis of carbohydrate benzylidene acetals. Synthesis of benzyl ethers of benzyl α- -, methyl β-D-mannopyranosides and benzyl α-D-rhamnopyranoside by ring cleavage of benzylidene derivatives with the LiAlH4-AlCl3 reagent

Treatment of benzyl α-(1) and methyl β- -mannopyranoside (2) with α,α-dimethoxytoluene gave the exo and endo isomers (3,5 and 4,6) of the dibenzylidene derivatives of 1 and 2. Hydrogenolysis of the exo isomers (3 and 5) with a molar equivalent of AlH₂Cl gave the 3-0-benzyl-4,6-0-benzylidene derivatives (7 and 21), whereas the endo isomers (4 and 6) gave the 2-0-benzyl-4,6-0-benzylidene compounds (8 and 22). The 2-0-allyl ether 9 of 7, the 3-0-allyl derivative (10) of 8 and compounds 21 and 22 were treated with an additional molar equivalent of AlH₂Cl at reflux and the products were the 4-0-benzyl-6-hydroxyl derivatives (11, 12, 23 and 24), whereas in the case of 22 the 6-0-benzyl-4-hydroxyl isomer (25) was also isolated. By deallylation of 11 and 12, 3,4-(13) and 2,4-di-0-benzyl (14) ethers of 1 were prepared. Tosylation of 11 and 12, and subsequent reduction of the products (15 and 16) made possible the preparation of the partially protected benzyl α- -rhamnopyranoside derivatives (17–20). The structures of the compounds synthesized were characterized by ¹H and ¹³C NMR spectroscopic investigation and by chemical methods.     

Synthesis of oligonucleotides with sequences identical with or analogous to the 3'-end of 16s ribosomal rna of escherichia coli: preparation op U-C-C-U-U-A and A-C-C-U-C-C-U-U-A via the modified phosphotriester method

The synthesis of oligoribonucleotides U-C-C-U-U-A and A-C-C-U-C-C-U-U-A, which are located at the 3'-terminus of 16S rRNA of E. coli, is described. The key-intermediates in the synthesis of these compounds are the fully-protected mononucleotides 5a-c, which can be rapidly (2–4 min) functionalized by either of the two following specific deblocking procedures: (i) at the 3'-tenninus with zinc in pyridine-2,4,6-triisopropylbenzenesul-phonic acid and (ii) at the 5'-terminus with 0.5M hydrazine in pyridine-acetic acid. The fully-protected hexamer 17a and nonamer 19, prepared by utilizing these deblocking conditions, were completely deprotected by the action of fluoride ion, followed by treatment with base and acid to give the required oligonucleotides in high yield.     

New strategy to the synthesis of (N → B) phenyl[N-alkyliminodiacetate-O,O′,N]boranes: The crystal structure of (N → B) phenyl[N-benzyliminodiacetate-O,O′,N]borane, (N → B)phenyl[N-(4-methyl)benzyliminodiacetate-O,O′,N]borane and (N → B) phenyl[N-phenacyliminodiacetate-O,O′,N]borane

A new, mild and friendly method for the synthesis of (N → B) phenyl[N-alkyliminodiacetate-O,O′,N]boranes 2–7 is reported. All compounds were identified by ¹H, ¹¹B, ¹³C NMR and their high resolution mass spectra (HRMS) are reported. The structure of the compounds 2, 4 and 5 were established by single crystal X-ray. Compounds 2 and 4 crystallized with two independent molecules 2A, 2B and 4A, 4B, respectively in the asymmetric unit. These molecular structures established the bicyclic structure showing a N → B bond length of 1.666 (2) Å for 2A, 1.675 (2) Å for 2B, 1.675 (3) Å for 4A, 1.663 (3) Å for 4B and 1.679 (2) Å for 5, as well as different torsion angles of the junction, 28.70 (2)° (C11–B1–N6–C17) for 2A, 21.50 (2)° (C11a–B1a–N6a–C17a) for 2B, 25.76 (0.26)° (C11–B1–N6–C17) for 4A, 21.96 (0.28)° (C11a–B1a–N6a–C17a) for 4B and −29.22 (0.20)° (C5–N1–B1–C13) for 5.     

Configurationally and conformationally homogeneous cyclic n-aryl sulfimides—IV : Synthesis,configuration and stereochemistry of the rearrangement of 1,3-di-thiane-1-N-p-chlorophenylimides

1,3-Dithiane-1-N-p-chlorophenylimides (1,4-9) were prepared and their configuration and conformation was determined by ¹H and ¹³C NMR. The compounds were rearranged to the corresponding 2-(2'-amino-5'-chlorophenyl)-1, 3-dithianes (1U,4U,9U). The rearrangement reactions took place with ?95% stereospecifity. The mechanism of the reaction was investigated with the aid of analogs specifically deuterated at C-2.     

η-Alkynyl and vinylidene transition metal complexes: 10. Reaction of the metal-acetylide [(η-C5H5)(CO)(NO)W---CC---C(CH3)3]Li with 1,2-diiodoethane as electrophile and with various nucleophiles

Treatment of the η¹-acetylide complex [(η⁵-C₅H₅)(CO)(NO)W---CC---C(CH₃)₃]Li (4) with 1,2-diiodoethane in THF at −78 °C, followed by the addition of Li---CC---R [R=C(CH₃)₃, C₆H₅, Si(CH₃)₃, 6a–6c] or n-C₄H₉Li and protonation with H₂O, afforded the corresponding oxametallacyclopentadienyl complexes (η⁵-C₅H₅)W(I)(NO)[η²-O=C(CC---R)CH=CC(CH₃)₃] (7a–7c), 8c and (η⁵-C₅H₅)W(I)(NO)[η²-O=C(n-C₄H₉)CH=CC(CH₃)₃] (9). The formation of these metallafuran derivatives is rationalized by the electrophilic attack of 1,2-diiodoethane onto the metal center of 4 to form first the neutral complex [(η⁵-C₅H₅)(I)(CO)(NO)W---CC---C(CH₃)₃] (5). Subsequent nucleophilic addition of Li---CC---R 6a–6c or n-C₄H₉Li and a reductive elimination step followed by protonation leads to the products 7a–7c and 9. One reaction intermediate could be trapped with CF₃SO₃CH₃ and characterized by a crystal structure analysis. The identity of another intermediate was established by infrared spectroscopic data. The oxametallacyclopentadienyl complex 10 forms in the presence of excess 1,2-diiodoethane through an alternative pathway and crystallizes as a clathrate containing iodine.     

Very slow rotation about a carbon-carbon single bond in o-tolyl-1,1'-diadamantylcarbinol and related compounds

Previous work on the ap and sp rotamers of o-tolyldi-t-butycarbinol (1a and 2a) has been extended to 1-adamantyl derivatives which are found to have abnormally high barriers to the ap → sp rotation. A semiquantitative explanation of the activation enthalpies for this conformational change is proposed Rotameric ap and spo-tolyl-1-adamantyl-t-butylcarbinols (1b and 2b) and o-tolyl-1,1'-diadamantylcarbinols (1c and 2c) are synthesised by the addition of o-tolyl-lithium to 1-adamantyl-t-butylketone and 1,1'-diadamantylketone, respectively. In both cases the major product is the less stable ap isomer. The rotation rates of 1b and 1c in dodecane correspond to activation energies of 33.9 and 39.1 kcal mol^?1, respectively, even higher than that for 1a, 29.8 kcal mol^?1. Steric energies are calculated by molecular mechanics for model structures corresponding to the ap and sp isomers and to two points on the rotation pathway, giving extrapolated theoretical activation enthalpies in qualitative agreement with the experimental data. The enhanced steric effect of the 1-Ad group can be attributed to three factors: restricted rotation of the methylene groups as opposed to the methyl groups in t-Bu increase in bond angle strain due to the terminal cyclohexane ring; increase in non-bonding interactions by buttressing effects of the terminal cyclohexane methine and methylene hydrogens.     

Synthesis and in vitro cytotoxic evaluation of some novel hexahydroquinoline derivatives containing benzofuran moiety

A series of new ethyl 4-(2-(benzofuran-2-yl)-4-substituted-1,4,5,6,7,8-hexahydroquinolin-1-yl)-benzoate 3a–c was synthesized by Michael condensation of benzofuran chalcones 1a–c and cyclohexanone to give 2-(2-benzofuranyl)-4-substituted-5,6,7,8-tetrahydro-4-H -chromene 2a–c, followed by reaction of the latter with ethyl 4-aminobenzoate. Condensation of 3a–c with different amines afforded the corresponding amides 4a–e. On the other hand, upon treatment compounds 3a–c with hydrazine hydrate gave the benzohydrazide derivatives 5a–c. The reaction of compounds 5a–c with different thio/isocyanate gave the corresponding thiosemicarbazide and semicarbazide derivatives 6a–c. Meanwhile compounds 5a–c were reacted with ethyl cyanoacetate and different β-dicarbonyl compounds such as acetyl acetone, ethyl acetoacetate, and diethyl malonate to afford pyrazolyl derivatives 7a, b; 8a, b; 9a, b; and 10a–c, respectively. Moreover, 5a–c were reacted with carbon disulfide to synthesize the corresponding oxadiazolyl derivatives 11a–c, while their condensation with different aromatic aldehydes gave the corresponding Schiff bases 12a–d. Cytotoxic evaluation of some of the newly synthesized compounds against human hepatocellular carcinoma cell lines (HepG-2) revealed that the tested compounds produce promising inhibitory effect against the growth of HepG-2 cells with IC₅₀ values ranged from 11.9 to 19.3 µg/mL.     

Synthesis of adamantane derivatives—43: 1,3-Dipolar cycloaddition reactivity of methyleneadamantane derivatives with substituted benzonitrile oxides

The 1,3-dipolar cycloaddition reactivity and regioselectivity of methyleneadamantane 1, ethyl adamantylideneacetate 7a, adamantylideneacetonitrile 7b and ω-methoxymethyleneadamantane 7c with substituted benzonitrile oxides 3a-i were calculated by CNDO/2 method using the perturbation equation derived by Klopman and Salem. The calculation predicted an exclusive formation of adamantan - 2 - spiro - 5' - 3' - aryl - Δ²' - isooxazoline 4a-i in the reactions of 1, 7a and 7b with 3a-i, and a formation of 67–69:33-31 mixture of 4a-i and isomeric 5a-i in the reaction of 7c with 3a-i. The predicted exclusive formation of 4a-i were experimentally observed in the reactions of 1,7a and 7b with 3a-i generated from 2a-i with Et₃N or thermally, but the reaction of 7c with 3a did not afford the corresponding adducts. A considerably higher reactivity of CN triple bond than CC double bond was observed in the reaction of 7b with 3a and 1,2,4-oxadiazole derivative 11 was obtained as the major product.     

The p-nitrophenylethyl (NPE) group: A versatile new blocking group for phosphate and aglycone protection in nucleosides and nucleotides

The syntheses of new monomer building blocks for oligonucleotide synthesis via the phosphotriester approach containing the p-nitrophenylethyl group for phosphate and aglycone protection are described. Blocking of the amide function in guanosines at O⁶ can be achieved by the Mitsunobu reaction forming the corresponding O⁶-p-nitrophenylethyl derivatives (4,5,10). Sugar-protected thymidine (16) and uridine (17) have been alkylated at O⁴ in an S_N1-type reaction by p-nitrophenylethyl iodide-silver carbonate in benzene to form the O⁴-p-nitrophenylethyl derivatives (18,19). Protection of the amino group in 2'-deoxycytidine (25) and cytidine (26) can be performed directly by 1-(p-nitrophenylethoxycarbonyl)-benzotriazole in DMF to obtain the corresponding carbamates (27,28) as a new type of N⁴-acylated cytidine derivative. p Nitrophenylethoxycarbonylation of the amino group in 2'-deoxyadenosine (33) and adenosine (34) requires previous sugar protection by acyl or silyl groups and can then be achieved by p-nitrophenylethyl chloroformate or better by 1-methyl-3-p-nitrophenylethoxycarbonylimidazolium chloride to form N⁶-p-nitrophenylethoxycarbonyladenosines (38,39,40,42). The various /-nitrophenylethyl blocking groups are stable under mild hydrolytic conditions (e.g. ammonia and triethylamine) but can be cleaved selectively by DBU or DBN in aprotic solvents. 5'-O-Monomethoxytritylation (12,29,43) as well as phosphorylations at the 3'-OH group can be effected to give the corresponding 3'-(2,5-dichlorophenyl,/-nitrophenylethyl)-phosphotriesters (13,22,30,44) also in high yields. Oximate cleavage of the latter compounds to the phosphodiesters (14,24,32,46) and detritylation to the 5'-unblocked phosphotriesters (15,23,31,45) do not affect the aglycone protecting groups, thereby demonstrating their general versatility. The newly synthesized compounds have been characterized on the basis of their elementary analyses (C, H, N), and UV- and ¹H-NMR-spectra.     

Furan derivatives—III : Synthesis and properties of β-ketosulphides and sulphur derivatives of chalcones of 5-nitrofuran series

A series of 2-(5-nitro-2-furyl)-2-oxoethylarylsulphides 3a–3h has been prepared by the reaction of 5-nitro-2-furylbromomethylketone 1 with 4-substituted thiophenols 2a–2h. The determined rates of carbanion formation (log k'), pK values as well as ¹H NMR data show that in these compounds transmission of polar effects by the substituents through the -S- group occurs. Compounds 3a–3h react with aromatic aldehydes affording sulphur chalcone derivativěs of the 5-nitrofuran series 4a–4h. ¹H NMR, IR and UV spectra of prepared compounds are discussed.