PhP-PPh group bound to 1,8-positions of naphthalene: Preparation of cis isomer and synthesis of binuclear complex

A thermodynamically less stable cis isomer of 1,2-diphosphacycle was prepared from the corresponding trans isomer. Diphosphine, in which a PhP-PPh bond bridges the 1,8-positions of naphthalene, 1,2-diphenyl-1,2-dihydronaphtho[1,8-cd][1,2]diphosphole (1), was first prepared according to a previously reported method, and the trans isomer of 1 was irradiated in tetrahydrofuran with UV-vis light to reach equilibrium with cis-1 in a trans:cis ratio of 1:2. When a similar photochemical conversion was carried out using a saturated hexane solution of trans-1, cis-1 was precipitated in a good yield of 94%. The configuration of cis-1 was confirmed by X-ray analysis. Both cis- and trans-1 diphosphine ligands were used for the preparation of binuclear gold complexes. The crystal structure of (μ-cis-1)-[AuCl]₂ demonstrated that the two lone pairs of cis-1 are suitably directed for arrangement of the two gold centers in close proximity to each other. The two independent (μ-cis-1)-[AuCl]₂ molecules in the crystal were found to form a dimer through the multiple intermolecular interaction among the gold centers.     

Photochemistry of 3,6-bis(styryl)pyridazines in solution and in neat liquid crystalline phase—optical switching and imaging techniques

3,6-Bis(styryl)pyridazines 1a-f with 2-6 alkoxy groups show on irradiation in solution a stereoisomerization which leads to a photostationary state of (E,E)- and (E,Z)-isomer. Sensitizing and quenching experiments reveal that the (E,E)→(E,Z) route is a pure triplet process, whereas the (E,Z)→(E,E) route can have a minor singlet by-reaction.Hexyloxy or dodecyloxy chains on the terminal benzene rings convey the (E,E)-isomers of compounds 1a,b,d-f thermotropic liquid crystalline properties. In particular S_A, S_C, and S_F/I phases were studied with regard to their photochemical behavior. Depending on the system, photodegradation of the smectic phase to the isotropic melt (S→I) or photoinduction of the smectic phase (I→S) can be achieved by alteration of the (E,E)/(E,Z) ratio. These processes represent the basis for imaging techniques (writing and erasing of information).     

Studies on inverse electron demand hetero Diels-Alder reaction of perfluoroalkyl 2(1H) pyridones with different dienophiles under microwave irradiation

The reaction of N-acetyl perfluoroalkyl substituted 2(1H) pyridones (7) with dimethylacetylenedicarboxylate (DMAD) on neutral alumina under solvent free microwave irradiation conditions extended to undergo an inverse electron demand hetero Diels-Alder reaction, however resulted exclusively in E, Z isomers (3:1) of Michael-type N-adducts (8). The similar reaction in case of 7a under thermal and photochemical conditions also gave the same products.     

Microwave-assisted synthesis of novel bis(2-thioxothiazolidin-4-one) derivatives as potential GSK-3 inhibitors

(5Z,5′Z)-3,3′-(1,4-Phenylenebis(methylene)-bis-(5-arylidene-2-thioxothiazolidin-4-one) derivatives (5a-r) have been synthesized by the condensation reaction of 3,3′-(1,4- or 1,3-phenylenebis(methylene))bis(2-thioxothiazolidin-4-ones) (3a,b) with suitably substituted aldehydes (4a-f) or 2-(1H-indol-3-yl)2-oxoacetaldehydes (8a-c) under microwave conditions. The bis(2-thioxothiazolidin-4-ones) were prepared from the corresponding primary alkyl amines (1a,b) and di-(carboxymethyl)-trithiocarbonyl (2). The 2-(1H-indol-3-yl)-2-oxoacetaldehydes (8a-c) were synthesized from the corresponding acid chlorides (7a-c) using HSnBu₃.     

An efficient microwave assisted synthesis of novel class of Rhodanine derivatives as potential HIV-1 and JSP-1 inhibitors

(Z)-5-(2-(1H-Indol-3-yl)-2-oxoethylidene)-3-phenyl-2-thioxothiazolidin-4-one (7a-q) derivatives have been synthesized by the condensation reaction of 3-phenyl-2-thioxothiazolidin-4-ones (3a-h) with suitably substituted 2-(1H-indol-3-yl)-2-oxoacetaldehyde (6a-d) under microwave condition. The thioxothiazolidine-4-ones were prepared from the corresponding aromatic amines (1a-e) and di-(carboxymethyl)-trithiocarbonyl (2). The aldehydes (6a-h) were synthesized from the corresponding acid chlorides (5a-d) using HSnBu₃.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Dimolybdenum complexes containing anions of N,N′-bis(pyrimidine-2-yl)formamidine and N-(2-pyrimidinyl)formamide

The reactions of Mo₂(O₂CCH₃)₄ with different equivalents of N,N′-bis(pyrimidine-2-yl)formamidine (HL1) and N-(2-pyrimidinyl)formamide (HL2) afforded dimolybdenum complexes of the types Mo₂(O₂CCH₃)(L1)₂(L2) (1) trans-Mo₂(L1)₂(L2)₂ (2) cis-Mo₂(L1)₂(L2)₂ (3) and Mo₂(L2)₄ (4). Their UV–Vis and NMR spectra have been recorded and their structures determined by X-ray crystallography. Complexes 2 and 3 establish the first pair of trans and cis forms of dimolybdenum complexes containing formamidinate ligands. The L1 ligands in 1–3 are bridged to the metal centers through two central amine nitrogen atoms, while the L2 ligands in 1–4 are bridged to the metal centers via one pyrimidyl nitrogen atom and the amine nitrogen atom. The Mo–Mo distances of complexes 1 [2.0951(17) Å], 2 [2.103(1) Å] and 3 [2.1017(3) Å], which contain both Mo?N and Mo?O axial interactions, are slightly longer than those of complex 4 [2.0826(12)–2.0866(10) Å] which has only Mo?O interactions.     

Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines 2a-d and 2f followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines 3a-d and 3f in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine (2e) gave pyrrolizidine 3b having the same stereochemistry as that obtained from the E isomer 2b.     

Convenient synthesis of 3-fluoro-4,5-diphenylfuran-2(5H)-one from benzoin ethers : Novel and efficient Z-E isomerisation and cyclisation of 2-fluoroalkenoate precursors, substitution of vinylic fluorine

Mixtures of ethyl (E)- and (Z)-4-alkoxy-2-fluoro-3,4-diphenylbut-2-enoates (6-8) prepared from benzoin ethers and ethyl 2-(diethoxyphosphoryl)-2-fluoroacetate were transformed in high yields to the target 3-fluoro-4,5-diphenylfuran-2(5H)-one (14) using bromine in tetrachloromethane at room temperature. The non-cyclisable Z-isomers 6b-8b were gradually isomerised to the cyclisable E-isomers 6a-8a during the process. The reaction of the (E)-butenoates 6a-8a with boron trifluoride led to furanone 14, while in Z-isomers 6b-8b both alkoxy group and vinylic fluorine were substituted with bromine during the reaction. Mechanisms for both complex reactions have been proposed. Furanone 14 was transformed to 2-[tert-butyl(dimethyl)silyloxy]-3-fluoro-4,5-diphenylfuran (18) as a novel building block.     

Stereoselective preparation of trisubstituted (Z)-alkenes; synthesis of the C17-C27 fragment of (−)-laulimalide

A Ni-catalyzed cross-coupling reaction of (Z)-5-(tert-butyldiphenylsilyl)oxy-3-bromo-1-trimethylsilyl-3-penten-1-yne (1) with alkyl Grignard reagent gives (Z)-3-alkyl-5-(tert-butyldiphenylsilyl)oxy-1-trimethylsilyl-3-penten-1-ynes (2) stereospecifically in good yields. The (Z)-enyne 2a is transformed in four steps to (Z)-3-methyl-5-silyloxy-3-pentenal (3), which is coupled with ketophosphonate 4 to give enone 13. The η-hydroxyallyl methanesulfonate derived from 13 is cyclized to 3,6-dihydro[2H]pyran by an intramolecular SN2′ reaction stereoselectively, furnishing a C17-C27 carbon unit of (−)-laulimalide.     

Trienylboronic acid, a versatile coupling tool for retinoid synthesis; stereospecific synthesis of 13-aryl substituted (11Z)-retinal

Trienylboronic acid 1a was prepared from iodotriene 3, which was coupled with (2Z,4Z)-3-aryl-5-iodo-2,4-pentadienol 9 by Suzuki coupling reaction to give geometrically pure 13-aryl substituted (11Z)-retinol 10. Oxidation of 10 gave 13-aryl substituted (11Z)-retinal 11.     

Increasing the antibacterial activity of gallium(III) against Pseudomonas aeruginosa upon coordination to pyridine-derived thiosemicarbazones

Reaction of N(4)-phenyl-2-formylpyridine thiosemicarbazone (H2Fo4Ph), N(4)-phenyl-2-acetylpyridine thiosemicarbazone (H2Ac4Ph) and N(4)-phenyl-2-benzoylpyridine thiosemicarbazone (H2Bz4Ph) with gallium nitrate gave [Ga(H2Fo4Ph)₂](NO₃)₃ (1), [Ga(2Ac4Ph)₂]NO₃ (2) and [Ga(2Bz4Ph)₂]NO₃ (3). In all complexes coordination of the thiosemicarbazone via the N_py–N–S chelating system occurs. In 1 the thiosemicarbazone acts as a neutral ligand while in 2 and 3 the ligand is anionic. Upon slow diffusion of 2 in DMSO [Ga(2Ac4Ph)₂]NO₃·DMSO (2a) was formed. The crystal structure of 2a was determined. Upon coordination the antibacterial activity of both gallium and thiosemicarbazones against Pseudomonas aeruginosa significantly increases.     

Silicon-carbon unsaturated compounds. 73. Photolysis of cis- and trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane in the presence of tert-butyl alcohol and acetone

Irradiation of cis-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1a) in the presence of tert-butyl alcohol in hexane with a low-pressure mercury lamp bearing a Vycor filter proceeded with high stereospecificity to give cis-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2a), in 33% isolated yield, together with a 15% yield of 1-[(tert-butoxy)methylphenylsilyl]-4-(methylphenylsilyl)butane (3). The photolysis of trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1b) with tert-butyl alcohol under the same conditions gave stereospecifically trans-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2b) in 41% isolated yield, along with a 12% yield of 3. Similar photolysis of 1a and 1b with tert-butyl alcohol-d₁ produced 2a and 2b, respectively, in addition to 1-[(tert-butoxy)(monodeuteriomethyl)(phenyl)silyl]-4-(methylphenylsilyl)butane. When 1a and 1b were photolyzed with acetone in a hexane solution, cis- and trans-2,3-benzo-1-isopropoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (4a and 4b) were obtained in 25% and 23% isolated yield. In both photolyses, 1-(hydroxymethylphenylsilyl)-4-(methylphenylsilyl)butane (5) was also isolated in 4% and 5% yield, respectively. The photolysis of 1a with acetone-d₆ under the same conditions gave 4a-d₆ and 5-d₁ in 18% and 4% yields.     

Preparation of new pyrido[3,4-b]thienopyrroles and pyrido[4,3-e]thienopyridazines

Two new types of pyrido-fused tris-heterocycles (1a,b and 2a,b) have been prepared from 3-aminopyridine in five/six steps. A synthetic strategy for the preparation of the novel pyrido[3,4-b]thieno[2,3- and 3,2-d]pyrroles (1a,b) and pyrido[4,3-e]thieno[2,3- and 3,2-c]pyridazines (2a,b) has been studied. The Suzuki cross coupling of the appropriate 2- and 3-thienoboronic acids (3,4) and 4-bromo-3-pyridylpivaloylamide (9) afforded the biaryl coupling products (10,11) in high yields (85%). Diazotization of the hydrolysed (2-thienyl)-coupling product (12) and azide substitution gave the 3-azido-4-(2-thienyl)pyridine intermediate (72%, 14). 3-Azido-4-(3-thienyl)pyridine (15) was prepared by exchanging the previous order of reactions. The desired β-carboline thiophene analogues (1a,b) were obtained via the nitrene by thermal decomposition of the azido precursors (14,15). By optimising conditions for intramolecular diazocoupling, the corresponding pyridazine products (72-83%, 2a,b) were afforded.     

Synthesis of N,N-di(arylmethylidene)arylmethanediamines by flash vacuum pyrolysis of arylmethylazides

Flash vacuum pyrolysis of arylmethylazides 7a-d gave 2,4-diazapentadienes 5a-d in high yield (76-92%). The thermal cyclization of 5a-d gave cis-imidazolines 1a-d, further heating or Swern oxidation of 1a-d gave dehydrogenated products, imidazoles 2a-d.     

Solvent-free reaction on KF-alumina under microwave: serendipitous one-pot domino synthesis of new isobenzofuran-1(3H)-ones from alpha-hydroxyketones

The reaction of four α-hydroxyketones 1a-d with a double equivalent of t-butyl acetylacetonate in the presence of KF-alumina under microwave irradiation afforded 6-acetyl-5-hydroxy-3,3-dialkyl-7-methyl isobenzofuran-1(3H)-ones 3a-d.     

A non-catalytic regioselective approach to the synthesis of (E)-stilbenes from suitably functionalized 2H-pyran-2-ones

Highly functionalized (E)-stilbenes 3a-m and 4-aryl-6-styryl-pyran-2-ylidineacetonitriles 4a-b have been prepared and delineated through the ring transformation of 6-aryl-3,4-disubstituted-2H-pyran-2-ones 1 with commercially available (E/Z)-4-phenyl-3-buten-2-one 2 without the use of any catalyst.     

Bioactive meroditerpenes and indole alkaloids from the soil fungus Neosartorya fischeri (KUFC 6344), and the marine-derived fungi Neosartorya laciniosa (KUFC 7896) and Neosartorya tsunodae (KUFC 9213)

Two new metabolites including a new aszonalenin analogue (1c) and a new meroditerpene (3) were isolated, together with aszonalenin (1a), acetylaszonalenin (1b), 13-oxofumitremorgin B (2), aszonapyrone A (4b) and helvolic acid, from the culture of the soil fungus Neosartorya fischeri (KUFC 6344). While the ethyl acetate extract of the culture of the diseased coral-derived fungus Neosartorya laciniosa (KUFC 7896) furnished aszonapyrone B (4a), aszonapyrone A (4b), tryptoquivaline L and 3′-(4-oxoquinazolin-3-yl) spiro[1H-indole-3,5′-oxolane]-2,2′-dione, the ethyl acetate extract of the culture of the marine sponge-associated fungus Neosartorya tsunodae (KUFC 9213) yielded a new analogue of chevalone C (5) and helvolic acid. The structures of the new compounds were established based on 1D and 2D NMR spectral analysis as well as HR-ESIMS. Compounds 1a–c, 2, 3, 4a, 4b and 5 were evaluated for their in vitro growth inhibitory activity on the MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and A375-C5 (melanoma) cell lines by the protein binding dye SRB method.     

Bismuth(III) bis(trifluoromethanesulfonyl)amide

Bismuth(III) bis(trifluoromethanesulfonyl)amide (Bi(NTf₂)₃, 3) has been prepared from the reaction of protiodemetallation of tri-p-tolylbismuth by a stoichiometric amount of bis(trifluoromethanesulfonyl)amine (1). The intermediates BiPh_3−n(NTf₂)_n (n=2 (4), 1 (5)) resulting from the reaction of 1 with triphenylbismuth have also been isolated. The amide 3 was able to catalyze the benzoylation and the benzenesulfonylation of toluene.     

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.