Syntheses and structures of iron carbonyl complexes derived from N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine and N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine

The reaction of N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine (1) with Fe₂(CO)₉ in refluxing acetonitrile yielded di-(μ₃-thia)nonacarbonyltriiron (2), μ-[N-(5-methyl-2-thienylmethyl)-η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido]hexacarbonyldiiron (3), and N-(5-methyl-2-thienylmethylidene)amine (4). If the reaction was carried out at 45 °C, di-μ-[N-(5-methyl-2-thienylmethylidene)-η¹(N);η¹(S)-2-thiolethylamino]-μ-carbonyl-tetracarbonyldiiron (5) and trace amount of 4 were obtained. Stirring 5 in refluxing acetonitrile led to the thermal decomposition of 5, and ligand 1 was recovered quantitatively. However, in the presence of excess amount of Fe₂(CO)₉ in refluxing acetonitrile, complex 5 was converted into 2-4. On the other hand, the reaction of N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine (6) with Fe₂(CO)₉ in refluxing acetonitrile produced 2, μ-[N-(6-methyl-2-pyridylmethyl)-η¹ (N_py);η¹:η¹(N); η¹:η¹(S)-2-thiolatoethylamido]pentacarbonyldiiron (7), and μ-[N-(6-methyl-2-pyridylmethylidene)-η²(C,N);η¹:η¹(S)-2- thiolethylamino]hexacarbonyldiiron (8). Reactions of both complex 7 and 8 with NOBF₄ gave μ-[(6-methyl-2-pyridylmethyl)-η¹(N_py);η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido](acetonitrile)tricarbonylnitrosyldiiron (9). These reaction products were well characterized spectrally. The molecular structures of complexes 3, 7-9 have been determined by means of X-ray diffraction. Intramolecular 1,5-hydrogen shift from the thiol to the methine carbon was observed in complexes 3, 7, and 9.     

Neomacrophorin and premacrophorin congeners from Trichoderma sp. 1212-03

Six novel neomacrophorin and four novel premacrophorin congeners were isolated from the fungus Trichoderma sp. 1212-03. Their planar structures and relative configurations were determined by conventional NMR and mass spectrometry techniques. The electronic circular dichroism (ECD) spectral comparisons with known neomacrophorins were effective for elucidating the structures of congeners carrying 2,3-epoxybenzoquinone (1, 2) and 2,3-epoxybenzosemiquinol substructures (3, 4, 5, 7, 8, and 9). The configuration of the 6-hydroxy-2-cyclohexene-1,4-dione moiety in 5′-deoxyneomacrophorin IV (6) was elucidated by NMR spectral comparison with those of known purpurogemutantidin (16) and mancrophorin F (17). This also resulted in the configurational revision of 16. The relative configuration of the 5,6-epoxy-2-cyclohexen-1,4-diol in premacrophorintriol-II (10) was determined by ¹³C chemical shift analysis using density functional theory calculations at the ωB97X-D/6-31G* level of theory. Compounds 1 and 6 exhibited potent cytotoxicity against human Caucasian colon adenocarcinoma cell line COLO 201.     

Synthesis of E and Z 1-amino-2-aryl(alkyl)-cyclopropanecarboxylic acids via meldrum derivatives

The reaction of 5-arylidene(alkylidene)-2,2-dimethyl-1,3-dioxane-4,6-diones (1) (Meldrum's acid derivatives) with dimethylsulfoxonium methylide gave 1- aryl(alkyl) - 6,6 - dimethyl - 4,8 - dioxo - 5,7 -dioxaspiro [2.5] octanes (2) which, on treatment with sodium methoxide or ammonium hydroxide, gave exclusively E-1-methoxy-carboyl-2-aryl-cyclopropanecarboxylic acids (4) or Z-1-carbamoyl-2-aryl(alkyl)-cyclopropanecarboxylic acids (7), respectively. Compounds, 4, under conditions of Curtius-type reactions, yielded Z-methyl 1-isocyanate-2-aryl-cyclopropanecarboxylates (5), while derivatives 7 were treated with hypobromite, leading to E-1-methoxy-carbonylamino-2-aryl(alkyl)-cyclopropanecarboxylic acids (8).Reaction of compounds 5 and 8 with hydrochloric acid produced the corresponding Z and E 1-amino-2-aryl (alkyl)-cyclopropanecarboxylic acids hydrochlorides (6). The ¹H-NMR spectral data were analyzed to deduce the stereochemistry of the compounds obtained.     

Reaction of chlorodithiophosphoric acid pyridiniumbetaine with adamantane derivatives containing amino group

Reactions of chlorodithiophosphoric acid pyridiniumbetaine, py.PS₂Cl (I) with 1-aminoadamantane (amantadine, Am) and 1-amino-3,5-dimethyladamantane (memantine, Mem), 1-(adamant-1-yl)ethylamine (rimantadine, Rim), and 1-aminomethyladamantane (amAd) were studied. New compounds – N,N′,N′′,N′′′-tetrakis(adamant-1-yl)trithiophosphoric acic tetraamide (II), N,N′,N′′,N′′′-tetrakis(3,5-dimethyladamant-1-yl)trithiophosphoric acid tetraamide (III), chlorodithiophosphoric acid 1-(adamant-1-yl)ethylamide pyridiniumbetaine (IV), pyridinium salt of 1,3-bis(adamant-1-yl)ethane-2,4-mercapto-2,4-dithioxo-1,3-diaza-2λ⁵,4λ⁵-diphosphetidine (V), N,N′,N′′,N′′′-tetrakis(adamant-1-ylmethyl)trithiophosphoric acid tetraamide (VI), and pyridinium salt of 1,2-bis(adamant-1-ylmethane)-4-mercapto-2,4-dithioxo-1-aza-3-thia-2λ⁵,4λ⁵-diphosphetidine (VII) – were prepared and characterized either/or by ³¹P NMR and infrared spectroscopy, the substances II a IV by X-ray diffraction analysis, III, V, VI, VII by MALDI TOF MS.     

Preparation of (8S)-8-fluoroerythronolide A and (8S)-8-fluoroerythronolide B,potential substrates for the biological synthesis of new macrolide antibiotics

Synthetic studies are reported in the erythromycin analogue area. Reaction of trifluoromethyl hypofluorite (CF₃OF) with 8,9-anhydroerythronolide A 6,9-hemiketal (1) or 8,9-anhydroerythronolide B 6,9-hemiketal (2) afforded, as major product, (8S)-8-fluoroerythronolide A 6,9;9,ll-spiroketal (3) or (8S)-8-fluoroerythronolide B 6,9;9,ll-spiroketal (4) and, as minor product, (8S)-8-fluoroerythronolide A (5) or (8S)-8-fluoroerythronolide B (6). Hydrolysis of 3 in boiling aqueous acetic acid gave 5, 9,10-anhydro-(8S)-8-fluoroerythronolide A 6,9-hemiketal (7), (8S)-8-fluoroerythronolide A 5,9;9,12-spiroketal (9) and 5,8-epoxy-8-epi-erythronolide A (10). Analogous range of products was obtained by acid hydrolysis of 4     

Chemo-, stereo- and regioselective hydrogenolysis of carbohydrate benzylidene acetals. Synthesis of benzyl ethers of benzyl α-d-, 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-d-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-d-rhamnopyranoside derivatives (17–20). The structures of the compounds synthesized were characterized by ¹H and ¹³C NMR spectroscopic investigation and by chemical methods.     

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.     

Novel generation and cycloaddition reactivity of N-phenylsulfonylbenzonitrilimine via thermal decomposition of N-(phenylsulfonyl)benzohydrazonoyl chloride

Thermal decomposition of N(phenylsulfonyl)-benzohydrazonoyl chloride (1) in refluxing toluene generated N-phenylsulfonylbenzonitrilimine (2) which gave 1,3-dipolar cycloadducts with ethyl (4a) and methyl acrylate (4b), acrylonitrile (4c), styrene (4d), norbornene (4e), and norbornadiene (4f). The reactions with 4a–d, 2 afforded regiospecifically 5-R substituted pyrazolines 5a–d in lower yields. The raction of 2 with 4e gave only exo adduct 5e, while the reaction with 4f gave both exo- (5f_x) and endo adducts (5f_n) as well as their retro-Diels-Alder product 6.     

Isolation,tentative identification,and synthesis studies of the volatile components of the hairpencil secretion of the monarch butterfly

The major volatile components of the hairpencil secretion of the male monarch butterfly have been identified as benzyl caproate and either 1, 5, 5, 9-tetramethyl-10-oxabicyclo[4.4.0]-3- decen-2-one(1), or 2, 2, 6, 8-tetramethyl-7-oxabicyclo[4.4.0]-4-decen-3-one(2). One sequence designed to synthesize 1 yielded two isomeric products of structure 1 whose spectra are very similar to each other but distinctly different from those of the natural product; this sequence also yielded a tricyclic ketal (9). A second sequence gave two epimeric spiro compounds (12) and a third sequence gave a [4.3.0] ring system (14).     

Synthesis and structural characterization of 1′-(diphenylphosphino)ferrocene-1-carboxamide, its corresponding hydrazide, some heterocycles derived from the hydrazide and palladium(II) complexes with these functional phosphinoferrocene ligands

Two polar phosphinoferrocene ligands, 1′-(diphenylphosphino)ferrocene-1-carboxamide (1) and 1′-(diphenylphosphino)ferrocene-1-carbohydrazide (2), were synthesized in good yields from 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) via the reactive benzotriazole derivative, 1-[1′-(diphenylphosphino)ferrocene-1-carbonyl]-1H-1,2,3-benzotriazole (3). Alternatively, the hydrazide was prepared by the conventional reaction of methyl 1′-(diphenylphosphino)ferrocene-1-carboxylate with hydrazine hydrate, and was further converted via standard condensation reactions to three phosphinoferrocene heterocycles, viz 2-[1′-(diphenylphosphino)ferrocen-1-yl]-1,3,4-oxadiazole (4), 1-[1′-(diphenylphosphino)ferrocen-1-carbonyl]-3,5-dimethyl-1,2-pyrazole (5), and 1-[1′-(diphenylphosphino)ferrocene-1-carboxamido]-3,5-dimethylpyrrole (6). Compounds 1 and 2 react with [PdCl₂(cod)] (cod = η²:η²-cycloocta-1,5-diene) to afford the respective bis-phosphine complexes trans-[PdCl₂(L-κP)₂] (7, L = 1; 8, L = 2). The dimeric precursor [(L^NC)PdCl]₂ (L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹) is cleaved with 1 to give the neutral phosphine complex [(L^NC)PdCl(1-κP)] (9), which is readily transformed into a ionic bis-chelate complex [(L^NC)PdCl(1-κ²O,P)][SbF₆] (10) upon removal of the chloride ligand with Ag[SbF₆]. Pyrazole 5 behaves similarly affording the related complexes [(L^NC)PdCl(5-κP)] (12) and [(L^NC)PdCl(5-κ²O,P)][SbF₆] (13), in which the ferrocene ligand coordinates as a simple phosphine and an O,P-chelate respectively, while oxadiazole 4 affords the phosphine complex [(L^NC)PdCl(4-κP)] (11) and a P,N-chelate [(L^NC)PdCl(4-κ²N³,P)][SbF₆] (14) under similar conditions. All compounds were characterized by elemental analysis and spectroscopic methods (multinuclear NMR, IR and MS). The solid-state structures of 1⋅½AcOEt, 2, 7⋅3CH₃CN, 8⋅2CHCl₃, 9⋅½CH₂Cl₂⋅0.375C₆H₁₄, 10, and 14 were determined by single-crystal X-ray crystallography.     

Incorporation of 5-substituted uracil derivatives into nucleic acids—III : Synthesis of 5-substituted uracils derived from 5-acetyluracil

5-Acetyluracil (1) has been converted into 5-(bromoacetyl)-uracil (2) by an established procedure. Reduction of 2 with sodium borohydride gave 5-(2-hydroxyethyl)uracil (4) in low yield. Treatment of 5-vinyluracil (7), obtained from 1 by published methods, with 1 molecular proportion of bromine followed by heating to 100°, gave E-5-(2-bromovinyl)uracil (8). Reaction of 8 with potassium t-butoxide gave 5(7)H-furanol[2,3,d]pyrimidin-6-one (10) and upon reduction with sodium in liquid ammonia, 8 gave 5-ethyluracil (11). Compound 2 showed low antibacterial activity against Staphylocuccus aureus, Streptococcus faecalis and Escherichia coli in nutrient broth and in a medium containing only inorganic salts, glucose and thymine, appreciable activity (～ 6 μg/ml) against E. coli. Compound 2 was not incorporated into the DNA of E. coli.     

Synthesis, IR-, NMR- and X-ray investigations on some novel N-hetaryl-dihydro-pyrazolyl ferrocenes. Study on ferrocenes, part 16

Cyclocondensation of 1-aryl-3-ferrocenyl-2-propen-1-ones (1) with hetaryl hydrazines resulted in N-hetaryl-3-aryl-5-ferrocenyl pyrazolines (3, 4). The analogous 3-aryl-1-ferrocenyl-2-propen-1-ones (5) gave the isomeric N-hetaryl-5-aryl-3-ferrocenyl-pyrazolines (6, 10), but in lower yield. The reaction of aryl-chalcones (7) with 4-hydrazino-phthalazinone led to 3,5-bis-aryl-N-hetaryl-pyrazolines (8) or to the corresponding ene-hydrazones (9). The structure of the new compounds was established by IR, ¹H and ¹³C NMR spectroscopy, including DNOE, HMQC, HMBC and DEPT methods. For compounds 1b, 3b and 8b the stereo structure was elucidated also by X-ray diffraction.     

Synthesis and structures of the dinuclear tin(II) complexes [R = Ph, X(Z) = CPh; R = SiMe3, X(Z) = PPh2] and of related compounds

Tin(II) compounds containing the ligands [CH(C₆H₃Me₂-2,5)C(Bu^t)NSiMe₃]⁻ (≡ L¹), [CH(Ph)C(Ph)NSiMe₃]⁻ (≡L²), [CH(SiMe₃)P(Ph)₂NSiMe₃]⁻ (≡ L³),

Full-size image (3K)

(≡ L⁴), [C(Ph)C(Ph)NSiMe₃]²⁻ (≡ L⁵), and [C(SiMe₃)P(Ph)₂NSiMe₃]²⁻ (≡ L⁶) are reported: the transient SnBr(L¹) (1) and SnBr(L²) (2), Sn(L¹)₂ (3) [P.B. Hitchcock, J. Hu, M.F. Lappert, M. Layh, J.R. Severn, J. Chem. Soc., Chem. Commun. (1997) 1189], the labile Sn(L²)₂ (4), [Sn(L⁵)]₂ (5), SnCl(L³) (6), Sn(L³)₂ (7), [Sn(L⁶)]₂ (8), Sn(L⁴)₂ (9) and Pb(L⁴)₂ (10). They were prepared from (i) SnBr₂ and K(L¹) (1, 3) or K(L²) (2, 4, 5); (ii) SnCl₂ and Li(L³) (6–9); or (iii) PbCl₂ and Li(L⁴) (10). Each of 1, 3 and 5–10 has been characterised by multinuclear NMR spectra; 3, 5, 6, 8, 9 and 10 by EI-mass spectra, but only 3, 5, 8, 9 and 10 were isolated pure and furnished X-ray quality crystals. Of greatest novelty are the title binuclear fused tricyclic ladder-like compounds 5 and 8. Quantum chemical calculations, on alternative pathways to 5 from 2 and to 8 from 7, are reported.     

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.     

A study of 1,5-hydrogen shift and cyclization reactions of an alkali isomerized methyl linolenoate

Heating a mixture formed by alkali isomerization of methyl linolenoate (1) produces a complex mixture with the bicyclic hexahydroindenoic esters 4β-(7-methoxycarbonylheptyl)-5α-methyl-2,3,3aα,4,5,7aαhexahydroindene (CL5) and 4β-ethyl-5α-(6-methoxycarbonylhexyl)-2,3,3aα,4,5,7aα-hexahydroindene (CL6) as main components. Similar isomerization reactions of three synthetic model compounds, methyl 9Z,13E,15Z-octadecatrienoate (2), 9Z,14E,16E-octadecatrienoate (4) and 9Z,11E,15Z-octadecatrienoate (5) corroborated the results obtained with alkali isomerized methyl linolenoate.     

Thio-acids—V : Some reactions of 3-oxo-1,2-dithioles

Diphenyldiazomethane with compound (1) gave dibenzoyl, while 2 and 3 gave the corresponding 3-oxo(2H)thiophenes 5. With copper-bronze 1 gave 2,2′-di-(thiobenzoate) (4), while 2 gave 2,7-diphenylthiepin (6a) and 2,5-diphenylthiophene (7a), but 3 gave only 2,5-di-(p-methoxyphenyl)thiophene (7b). With Grignard reagents 1 gave the corresponding methanol derivative 14, while 2 gave the thiobenzoylethylenes 13a and b, but 3 gave 2,7-di-(p - methoxyphenyl) - 4,4,5,5- tetraphenyl(4H)thiepin (15). The reaction mechanisms are discussed.     

Benzolactams—I : Alkylation of 1,2,4,5-tetrahydro-3-methyl-3h-3-benzazepin-2-one with sodium hydride and alkyl halide

Alkylation of 1,2,4,5-tetrahydro-3-methyl-3H-3-benzazepin-2-one 1a with various halides and sodium hydride in tetrahydrofuran-dimethylformamide solvent system was studied. Primary halides predominantly provided the 1-mono-substituted products, such as alkyl (2a-g, p, q), allyl (2j, k), propargyl (21) and benzyl (2m-o) derivatives, in satisfactory yields, and secondary halides resulted in lower yields (2h, i) than primary halides. In attempted dialkylations with ω, ω'-dibromoalkanes, 5- and 6-membered spiro products (4c, d) were obtained by this method. The Michael type addition reaction was also studied and it was found that acrylic acid esters gave the corresponding adducts (2p, q).     

Synthesis of 3,9-dialkylguanines and their conversion into 3-alkylwyes,models for the fluorescent nucleosides from phenylalanine transfer ribonucleic acids

Synthesis of 3,9-dialkylguanines 5 has been accomplished by N-cyanation of 1-alkyl-5-(alkylamino)imidazole-4- carboxamides 3 followed by base-catalysed cyclisation. Cyclocondensation of 9-alkyl-3-methylguanines 5a, d, f with MeCOCH₂Br gave 3-alkylwyes 6, model compounds of the most probable structure for wyosine from Torulopsis utilis tRNA^Phe.     

Synthese von Tricarbonyl-η5-cyclohexadienyl-wolframat und Tricarbonyl-η5-cyclohexadienyl-methyl-wolfram

η⁶-Arene-tricarbonyl-tungsten (arene = benzene (1a), toluene (1b), m-xylene (1C), P-xylene (1D), o-xylene (1E), mesitylene (1F)) yield with potassium-tri-sec-butylboranate correspondingly methyl-substituted tricarbonyl-η⁵-cyclohexadienyl-tungstates (2A–2F). Similarly 1A reacts with methyllithium to tricarbonyl-η⁵-anti-6-methylcyclohexadienyl-tungstate (4A). In THF 2A–2F and 4A are converted by methyliodide to tricarbonyl-μ⁵-cyclohexadienyl-tungsten (3A–3F) and tricarbonyl-η⁵-anti-6-methylcyclophexadienyl-methyl-tungsten (5A). The complexes were characterized by C, H elemental analyses and by IR and ¹H-NMR spectroscopy.     

A new route to thiopyran S,S-dioxide derivatives via an overall ring-enlargement protocol from 3-nitrothiophene

(1E,3Z)-1-Aryl-4-methanesulfonyl-2-nitro-1,3-butadienes (8), derived from the initial ring-opening of 3-nitrothiophene (5), have been found to undergo a facile base-induced cyclization leading to thiopyran S,S-dioxides (9), thus furnishing a further example of effective ring-enlargement from 5- to 6-membered sulfur heterocycles. Compounds 9 are obtained as single racemic mixtures in satisfactory yields; they still contain a nitrovinylic moiety, which can be exploited for further modifications targeted to new derivatives endowed with either synthetic or pharmacological potentialities e.g., in the field of L-type Ca²⁺-channel blockers.