A one-pot, two step synthesis of 2,2-disubstituted 1-nitroalkenes

The reactions of ketones 1a-o, nitromethane 2, and a stoichiometric amount of piperidine 3a or ethylenediamine 3b in the presence of mercaptan 6a in THF or CH₃CN solution give high yields of β-nitrosulfides 7a-o. The latter can be oxidized by 8a (m-CPBA or m-CPBA/AcOH) at 0°C, 8b (H₂O₂/AcOH), or 8c (H₂O₂) at room temperature, thus generating β-nitroalkylsulfoxides 9a-o, which then undergo elimination to produce medium to high yields of 2,2-disubstituted-1-nitroalkenes 5a-o, when refluxed in a solution of ClCH₂CH₂Cl (1,2-dichloroethane). After preparation from 1a-o, 2, 3, and 6a, 7a-o were oxidized with 8a, 8b, or 8c in a mixture of CH₃CN and ClCH₂CH₂Cl to generate β-nitrosulfoxides 9a-o, which then underwent elimination under refluxing under one-pot conditions. Compounds 14 and 15g were also prepared using 13, 2, 3b, and 6, in a similar manner.     

Light-harvesting composites of directly connected porphyrin-phthalocyanine dyads and their coordination dimers

Directly linked porphyrin (Por)-phthalocyanine (Pc) heterodyads (H₂Por-H₂Pc and H₂Por-ZnPc) with an imidazolyl group at porphyrin’s meso-position were synthesized. Introduction of a zinc ion into the porphyrin afforded stable complementary dimers of the heterodyads. The heterodyads and their dimers gave extensive and strong absorption bands owing to the porphyrin and phthalocyanine components and induced an efficient energy transfer from porphyrin to phthalocyanine. Strong fluorescence from phthalocyanine was observed in the case of H₂Por-H₂Pc.     

Palladium complexes of N-aryl-2-pyridylamines

Palladium complexes of N-phenyl-2-pyridylamine (4) and dipyridylamine substrates (7, 11) have been studied. Due to the coordination ability of the pyridine-nitrogen atoms, the pyridyl substrates, 4, 7, 11 were subjected to Pd(OAc)₂ complexations and a number of N-aryl-2-pyridylamine Pd complexes (13-17) were isolated and characterised, in particular by NMR and ESI-MS. A new method for the preparation of the acetato-bridged six-membered ring palladacycle complex (13) of 4 is reported. The dipyridyl amines 7, 11 formed cis/trans bis-dentate acetato-bridged dimeric Pd₂Lig₂(OAc)₂ (14a,b/16a,b) and Pd₃Lig₂(OAc)₄ complexes (15a,b/17a,b). The N-aryl-2-pyridylamine substrates (4, 7, 11) were prepared by oxidative nucleophilic substitution, by 1,3-cycloaddition reaction or by Buchwald amination.     

Syntheses of a stable tristibine and of related antimony compounds with the 2,6-dimesitylphenyl (Dmp) substituent

DmpSbBr₂ (Dmp = 2,6-Mes₂C₆H₃) (1) is obtained by the reaction of DmpMgBr with SbCl₃. The reaction of 1 with KI in ethanol gives DmpSbI₂ (2). Dmp(Ph)SbBr (3) is prepared from DmpMgBr and PhSbCl₂. Compound 1 or 3 react with LiAlH₄ to form DmpSbH₂ (4) or Dmp(Ph)SbH (5). Compound 4 reacts with MeI in presence of DBU to give Dmp(Me)SbH (6). DmpSb(SbMe₂)₂ (7) is obtained from 4 and Me₄Sb₂. Elimination of hydrogen from 6 gives [Dmp(Me)Sb]₂ (8). Hydrolysis of 3 gives Dmp(Ph)SbOH (9). The molecular structures of 1-3, 5, 8 and 9 were determined by X-ray diffraction on single crystals.     

Half-sandwich η-arene–ruthenium(II) complexes bearing 1-alkyl(benzyl)-imidazo[4,5-f][1,10]-phenanthroline (IP) derivatives: the effect of alkyl chain length of ligands to catalytic activity

The reaction of bromoalkanes (R–Br; (3), R=C_nH_2n+1, n=4 (a), 8 (b), 12 (c),18 (d)) and bromobenzyl derivatives (R′–Br; (4), R′=CH₂C₆H₂(CH₃)₃-2,4,6 (a); CH₂C₆H(CH₃)₄-2,3,5,6 (b); CH₂C₆(CH₃)₅ (c)) with 1H-imidazo[4,5-f][1,10]-phenanthroline (IP)(L₂) gave the corresponding 1-R-imidazo[4,5-f][1,10]-phenanthroline (IPR)(L_3a–d) and 1-R′-imidazo[4,5-f][1,10]-phenanthroline(IPR')(L_4a–c) ligands, respectively. Treatment of L_3a–d and L_4a–d with [Ru(p-cymene)Cl₂]₂ led to the formation of [Ru(p-cymene)(IPR)Cl]Cl (RuL_3a–d) and [Ru(p-cymene)(IPR′)Cl]Cl (RuL_4a–c). New ruthenium(II) complexes RuL_3a–d and RuL_4a–c were characterized by elemental analysis, FTIR, UV–visible and NMR spectroscopy. In order to understand effects of these changes on the N-substituent of imidazol on IP and how they translate to catalytic activity, these new RuL₂, RuL_3a–d and RuL_4a–c were applied in the transfer hydrogenation of ketones by 2-propanol in presence of potassium hydroxide. The activities of the catalysts were monitored by NMR and GC analysis.     

Synthesis and reactivity of new functionalized Pd(II) cyclometallated complexes with boronic esters

Treatment of the functionalized Schiff base ligands with boronic esters 1a, 1b, 1c and 1d with palladium (II) acetate in toluene gave the polynuclear cyclometallated complexes 2a, 2b, 2c and 2d, respectively, as air-stable solids, with the ligand as a terdentate [C,N,O] moiety after deprotonation of the -OH group. Reaction of 1j with palladium (II) acetate in toluene gave the dinuclear cyclometallated complex 5j. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species 3a, 3b, 3c, 3d and 6j with cleavage of the polynuclear structure. Treatment of 2c with the diphosphine Ph₂PC₅H₄FeC₅H₄PPh₂ (dppf) in 1:2 molar ratio gave the dinuclear cyclometallated complex 4c as an air-stable solid.Deprotection of the boronic ester can be easily achieved; thus, by stirring the cyclometallated complex 3a in a mixture of acetone/water, 3e is obtained in good yield. Reaction of the tetrameric complex 2a with cis-1,2-cyclopentanediol in chloroform gave complex 2c after a transesterification reaction. Under similar conditions complexes 3a and 3d behaved similarly: with cis-1,2-cyclopentanediol, pinacol or diethanolamine complexes 3c, 3b, 3g and 3f, were obtained. The pinacol derivatives 3b and 3g experiment the Petasis reaction with glyoxylic acid and morpholine in dichloromethane to give complexes 3h, and 3i, respectively.     

Synthesis of functionalized bicyclo[3.2.1]octan-6-ones for diterpenoids: allylsilane directed Pummerer reaction: insertion reactions of diazoketones

The sulfide 5 underwent Pummerer cyclization to give 6, whereas the allyl silane analog 10 produced the bicyclo[3.2.1]octanones 11 and 11a. Extension of this methodology to 15 resulted in 16 without the necessity for allyl silane activation. The intermediate diazoketone 14 on treatment with BF₃·OEt₂ gave 17, 18 and 19, whereas the saturated adduct 22 on treatment with Rh₂(OAc)₄ gave 23.     

Linkage position influences of anthracene and tricyanovinyl groups on the opto-electrical and photovoltaic properties of anthracene-based organic small molecules

Anthracene-based small molecules incorporating an electron accepting tricyanovinyl (TCV) group was prepared to investigate the linkage position influences of the anthracene and TCV groups on the opto-electrical and photovoltaic properties of the molecules. The maximum absorptions of the anthracene-based molecules incorporating the TCV group at the phenyl group of the triphenylamine unit (TCV-TpaA_9,10T, TCV-TpaTA_9,10T, and TCV-TpaA_2,6T) or at the thiophene unit (TpaA_9,10T-TCV, TpaTA_9,10T-TCV, and TpaA_2,6T-TCV) were found to be dependent on the linkage position of the anthracene unit. The HOMO energy levels of the molecules containing TCV group at the phenyl group of the triphenylamine unit were deeper than those of the molecules containing TCV group at the thiophene unit. The solution processed small molecule organic solar cells (SMOSCs) prepared with the structure of ITO/PEDOT:PSS/TCV-TpaA_9,10T or TCV-TpaA_2,6T or TpaA_2,6T-TCV:PC₇₁BM (2:1 wt %)/LiF/Al exhibited a maximum energy conversion efficiency of 1.04%, 1.67%, and 1.95%, respectively, under AM 1.5 irradiation (100 mW cm⁻²).     

A facile approach for the synthesis of novel substituted 4H-chromenes and condensation reactions of 4H-chromenes leading to chromenopyrrolones and triazolylchromenopyrrolones

A facile method has been developed for the synthesis of 4H-chromene-3-carboxylates 3a–d by the nucleophilic substitution reaction of 2-hydroxy-2H-chromene-3-carboxylates 2a–d with triethylsilane in the presence of BF₃·O(C₂H₅)₂. Cyclocondensation of 4H-chromene-3-carboxylates 3a–d with benzylamines 4a–d afforded a series of 2,3-dihydrochromenopyrrolones 5a–p and with propargylamine afforded 2-propynyl-2,3-dihydrochromenopyrrolones 6a–d. Click reaction of 6a–d with benzyl azides 7a–d provided a series of 1H-1,2,3-triazolylmethyl-2,3-dihydrochromenopyrrolones 8a–p. Thus synthesized compounds 3a–d, 5a–p, 6a–d, and 8a–p are novel heterocyclic compounds and being reported for the first time.     

Amphiphilic perfluoroalkylated sulfones and sulfonate betaines

Two types of perfluoro alkyl-containing amphiphilic sulfones 7-9 and 13-15, respectively, and sulfonate betaines 23-32 were prepared using 2-[(perfluoroalkyl)methyl]oxiranes (1-3, R_F = C₄F₉, C₆F₁₃, C₈F₁₇) or 3-(perfluoroalkyl)propyl iodides (16 and 17, R_F = C₆F₁₃, C₈F₁₇) as the starting compounds. The overall yields of two-step syntheses were above 90%. The compounds 7-9 were prepared by the reaction of oxiranes 1-3 with 2-sulfanylethan-l-ol and subsequent oxidation of intermediate sulfides. Similarly, the amphiphiles 13-15 were obtained by analogous reaction of oxiranes 1-3 with thiomorpholine and subsequent oxidation of the sulfur atom in the morpholine ring. In the syntheses of betaines 23-32, the starting compounds 1-3 or 16 and 17 were first reacted with dimethylamine followed by the ring-opening reaction of the intermediate fluoroalkyl(dimethyl)amines with propane-1,3- or butane-1,4-sultones.     

Metal-organic coordination architectures of azole heterocycle ligands bearing acetic acid groups: Synthesis, structure and magnetic properties

Four new coordination complexes with azole heterocycle ligands bearing acetic acid groups, [Co(L¹)₂]_n (1), [CuL¹N₃]_n (2), [Cu(L²)₂·0.5C₂H₅OH·H₂O]_n (3) and [Co(L²)₂]_n (4) (here, HL¹=1H-imidazole-1-yl-acetic acid, HL²=1H-benzimidazole-1-yl-acetic acid) have been synthesized and structurally characterized. Single-crystal structure analysis shows that 3 and 4 are 2D complexes with 4⁴-sql topologies, while another 2D complex 1 has a (4³)₂(4⁶)-kgd topology. And 2 is a 3D complex composed dinuclear μ_1,1-bridging azido Cu^II entities with distorted rutile topology. The magnetic properties of 1 and 2 have been studied.     

Structural diversity in the self-assembly of Ag(I) complexes containing 2-amino-5-halopyrimidine

A series of Ag(I) complexes containing the 2-amino-5-halopyrimidine ligands have been synthesized and their structures characterized by X-ray crystallography. The isomorphous complexes Ag(L-Cl)₂(CF₃SO₃) (L-Cl = 2-amino-5-chloropyrimidine), 1, and Ag(L-Br)₂(CF₃SO₃) (L-Br = 2-amino-5-bromopyrimidine), 2, are mononuclear, while [Ag(L-Br)(CF₃SO₃)]₆·6C₄H₁₀O, 3, and [Ag(L-I)(CF₃SO₃)]₆ (L-I = 2-amino-5-iodopyrimidine), 4, show cyclic self-assembly of six Ag(Ι) atoms and six L-X ligands, resulting in 24-membered metallocycles. The complex [Ag(L-I)(CF₃SO₃)]_∞, 5, forms 1D zigzag chains which are linked through C-I?Ag and Ag?O interactions to form a 3D structure. The tetranuclear complexes [Ag(L-X)(NO₃)]₄ [X = Cl, 6; Br, 7] form 16-membered metallocycles, while [Ag(L-X)(ClO₄)]_∞ [X = Cl, 8; Br, 9] exhibit helical chains. The different structure of 5 from 1 and 2 appears to be due to the stronger nucleophilic character of the iodine atom. In these complexes, the relatively smaller NO₃⁻ anions lead to the formation of tetranuclear metallocycles and the larger CF₃SO₃⁻ anions support the hexanuclear metallocycles, whereas the ClO₄⁻ anions induce the helical chains.     

A glycal approach towards an efficient and stereodivergent synthesis of polyhydroxypyrrolidines

A stereo-defined synthesis of two diastereomers of polyhydroxypyrrolidines from 3,4,6-tri-O-benzyl-d-glucal 4 involving a cleavage-recyclization strategy is reported. Hemiacetal 7 obtained from glucal 4, upon reduction with LiAlH₄ afforded diol 8. Selective acetylation of 8 to 11, followed by Mitsunobu cyclization yielded the diversely protected polyhydroxypyrrolidine 12. Oxidation of 11 and subsequent stereoselective reduction led to 20, the C-5 epimer of 11, which upon Mitsunobu cyclization gave polyhydroxypyrrolidine 21. Selective deprotection of the acetyl groups of 12 and 21 were carried out using Na₂CO₃ in MeOH. Polyhydroxypyrrolidines 12 and 21 upon heating with an excess of Mg in MeOH underwent simultaneous N-detosylation and deacetylation to afford amino alcohols 15 and 24, respectively, in quantitative yield. Catalytic hydrogenation of 15 and 24 provided quantitatively the polyhydroxypyrrolidines 2 and 3, respectively.     

Chemically modified oximato complexes of titanium(IV) isopropoxide as new precursors for the sol-gel preparation of nano-sized titania: Crystal and molecular structure of [Ti{ONC10H16}4·2CH2Cl2]

Reactions of [Ti(OPrⁱ)₄] with various oximes, in anhydrous refluxing benzene yielded complexes of the type [Ti{OPrⁱ}_4−n{L}_n], where, n = 1-4 and LH = (CH₃)₂CNOH (1-4), C₉H₁₆CNOH (5-8) and C₉H₁₈CNOH (9-12). The compounds were characterized by elemental analyses, molecular weight measurements, FAB-mass, FT-IR and NMR (¹H, ¹³C{¹H}) spectral studies. The FAB-mass spectra of mono- (1), and di- (2), (6), (10) substituted products indicate their dimeric nature and that of tri- (3) and tetra- (4), (8) substituted derivatives suggest their monomeric nature. Crystal and molecular structure of [Ti{ONC₁₀H₁₆}₄·2CH₂Cl₂] (8A) suggests that the oximato ligands bind the metal in a dihapto η²-(N, O) manner, leading to the formation of an eight coordinated species. Thermogravimetric curves of (3), (6) and (10) exhibit multi-step decomposition with the formation of TiO₂ as the final product in each case, at 900 °C. Low temperature (∼600 °C) sol-gel transformations of (2), (3), (4), (6), (7) and (8) yielded nano-sized titania (a), (b), (c), (d), (e) and (f), respectively. Formation of anatase phase in all the titania samples was confirmed by powder XRD patterns, FT-IR and Raman spectroscopy. SEM images of (a), (b), (c), (d), (e) and (f) exhibit formation of nano-grains with agglomer like surface morphologies. Compositions of all the titania samples were investigated by EDX analyses. The absorption spectra of the two representative samples, (a) and (f) indicate an energy band gap of 3.17 eV and 3.75 eV, respectively.     

Formal total synthesis of aspergillide A

The formal total synthesis of aspergillide A 1 is described. The cross-metathesis of enone 6 with 6-hepten-2-ol derivative 5 provided E-olefin 15 corresponding to the C₄-C₁₄ backbone of 1. The CBS asymmetric reduction of 15 gave allyl alcohol 16, which was transformed into β-alkoxyacrylate 4 which had a formyl group. SmI₂-induced reductive cyclization of 4 gave a 2,6-syn-2,3-trans THP derivative 3 in good yield. After methoxymethylation of 3, the resulting compound 19 was submitted to desilylation and hydrolysis, to afford Fuwa’s key intermediate 2 for the total synthesis of 1.     

Dibromomethane as one-carbon source in organic synthesis: a versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes

Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH₂Br₂-Et₂NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.     

Chiroptical switching system based on the host-guest interaction between metal cations and poly(phenylacetylene)s bearing polycarbohydrate ionophore

Polycarbohydrate macromonomers with different degrees of polymerization (DP), that is, end-functionalized (1 → 6)-2,5-anhydro-3,4-di-O-ethyl-d-glucitols with 4-ethynylbenzoyl groups (macromonomer 2: DP = 6.6, and macromonomer 3: DP = 9.5) were synthesized. The copolymerizations of these macromonomers and phenylactylene (PA) were carried out in various molar ratios to give poly(phenylacetylene)s bearing a polycarbohydrate ionophore as the graft chain with various grafting rates, poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y). These polymers showed split-type circular dichroism (CD) spectra in the long absorption region of the conjugated polymer backbones (280-500 nm). This indicated that poly-(2_x-co-PA_y) and poly-(3_x-co-PA_y) had predominantly one-handed helical conformations in the backbones. The CD spectral patterns of these polymers were inverted in the presence of metal cationic guest molecules. On the other hand, control experiments using poly(phenylacetylene)s bearing a monocarbohydrate (poly-(4_x-co-PA_y)) and metal cations did not show such a CD spectral inversion. These results clearly indicated that the chiroptical switching of the poly(phenylacetylene)s bearing polycarbohydrate ionophore was attributable to the host-guest complexation of the polycarbohydrate ionophore with metal cations.     

Triphenyl lead, tin and germanium coordination compounds derived from 9H-3-thia-1,4a,9-triaza-fluorene-2,4-dithione

Reactions of potassium 4-thioxo-3-thia-1,4a,9-triaza-fluorene-2-thiolate with Ph₃PbCl, Ph₃SnCl and Ph₃GeCl provided the corresponding metal pentacoordinated compounds 2-4. Addition of THF afforded their hexacoordinated derivatives (5-7). Adducts of 2 and 3 with DMSO (8, 10), pyridine (9, 11), Ph₃PO (12, 14) CH₃OH (13, 15), respectively were synthesized. Compound 2 afforded the H₂O adduct (16). In all cases the metal atom is chelated by the ligand through a covalent bond with S2 and a coordination bond with N1 forming four membered rings. Compounds were identified by ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn and ²⁰⁷Pb. X-ray diffraction structures of 2, 3, 8, 9, 11, 14 and 16 were obtained.     

Addition of 2-tert-butyldimethylsilyloxythiophene to activated quinones: an approach to thia analogues of kalafungin

The uncatalyzed reaction of 2-tert-butyldimethylsilyloxythiophene 2 with 1,4-quinones bearing either an electron withdrawing acetyl or a carbomethoxy group at C-2, was investigated. No reaction was observed using 1,4-quinones 8 and 9 bearing an ester group at C-2 whereas use of 1,4-quinones 10 and 11 bearing an acetyl group at C-2 only provided low yields of the silyloxythiophenes 15 and 16 resulting from electrophilic substitution of the silyloxythiophene by the 1,4-quinone. Use of the Lewis acids InCl₃, Cu(OTf)₂ and BF₃·Et₂O were investigated in an effort to improve the yield of the desired annulation reaction. BF₃·Et₂O proved to be the optimum catalyst for the synthesis of thiolactone naphthofuran adducts 14 and 18 from 1,4-naphthoquinones 9 and 11, respectively. Reaction of 2-tert-butyldimethylsilyloxythiophene 2 with 1,4-benzoquinones 8 and 10 bearing a carbomethoxy or an acetyl group at C-2, respectively, afforded thiolactone benzofuran adducts 13 and 17, respectively, catalyzed by either InCl₃ or Cu(OTf)₂. Addition of 2-tert-butyldimethylsilyloxythiophene 2 to 3-acetyl-5-methoxy-1,4-naphthoquinone 12 afforded adduct 19 that underwent oxidative rearrangement to thiolactone pyranonaphthoquinone 20 using ceric ammonium nitrate in acetonitrile, thus providing a novel approach for the synthesis of a thia analogue of the pyranonaphthoquinone antibiotic kalafungin.     

Synthesis, photophysical properties, and cyanide detection in aqueous solution of BF2-curcumin dyes

Derivatives of difluoroboron curcumin (BF₂-curcumin, BF₂-cur(OMe)₂, BF₂-cur(OTs)₂, and BF₂-curOTs), were synthesized. All compounds possessed electron donor moieties at both ends of the conjugated π system and an electron acceptor moiety in the middle of the molecules (D-A-D system) and should exhibit different optical properties depending on substituents on the benzene rings. Photophysical properties of curcumin and difluoroboron curcumin derivatives were explored. The electron-withdrawing substituent could decrease the electron acceptability of BF₂-acceptor moiety resulting in the hypsochromic shift of both absorption and emission bands. BF₂-curcumin and BF₂-cur(OMe)₂ displayed the positive solvatochromic effect relying predominantly on polarity and polarizability of the solvent. Interestingly, BF₂-curcumin showed high selectivity and sensitivity towards cyanide with the detection limits of 22 μM and 0.14 μM measured by visual detection and UV-vis spectrophotometry, respectively. Compared to the original curcumin, BF₂-curcumin offered a remarkably promising detection of cyanide with 66-fold enhancement in aqueous media (4:1 of CH₃CN/H₂O).