Stereocontrolled and Versatile Total Synthesis of Bispyrrolidinoindoline Diketopiperazine Alkaloids: Structural Revision of the Fungal Isolate (+)‐Asperdimin

Homo‐ and heterodimeric bispyrrolidinoindoline diketopiperazine alkaloids have been synthesized following a concise, versatile, and stereoselective route. Highlights of the sequence are a diastereoselective construction of the C3a‐bromo‐hexahydropyrrolo[2,3‐b]indole nucleus, its Co^I‐induced C3a? C3a′ dimerization, and the twofold or sequential amide‐bond formation before cyclization to the diketopiperazine of the homo‐ or heterodimeric alkaloids, respectively. Stereochemical diversity is achieved through the choice of the appropriate amino acids combined with the base‐induced epimerization of the C2‐acyl‐hexahydropyrrolo[2,3‐b]indole at C2. According to this strategy, the natural products (+)‐WIN 64821 1 , (+)‐WIN 64745 2 and (+)‐asperdimin 6 as well as analogues ( 5 , 22 , 32 , 44 ) with different relative and absolute configuration have been efficiently synthesized. The flexibility of this synthetic methodology has facilitated the structural revision of the natural product (+)‐asperdimin, whose structure has been corrected to diastereomer 6 .     

Isolation and structure determination of a new diketopiperazine dimer from marine-derived fungus Aspergillus sp. SF-5280

A new diketopiperazine dimer designated as SF5280-415 (1) was isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5280 by various chromatographic methods. The structure of 1 was mainly determined by analysis of the NMR spectroscopic data and MS data, along with Marfey’s method. This compound is a new diastereoisomer of known bispyrrolidinoindoline diketopiperazine alkaloid WIN 64745, which possesses unique architecture biosynthetically derived from an indole oxidation reaction of tryptophan.     

Expedient total syntheses of WIN 64745 and WIN 64821

Bispyrrolidinoindoline diketopiperazine alkaloids were synthesized from a common intermediate in seven steps from commercially available amino acids. This versatile synthetic strategy has led to the accomplishment of the first total synthesis of heterodimeric WIN 64745 and a novel approach to homodimeric WIN 64821.     

Synthesis and Characterization of Heteroleptic Ru(II) Complexes Based on 4,4′‐Bis((E)‐styryl)‐2,2′‐bipyridine as Ancillary Ligand and Application for Dye‐Sensitized Solar Cells

Heteroleptic Ru(II) complexes were designed based on 4,4′‐bis((E)‐styryl)‐2,2′‐bipyridine (bsbpy) as an ancillary ligand for dye‐sensitized solar cells (DSSCs), and those Ru(II) sensitizers, [Ru(L)(bsbpy)(NCS)₂][TBA] (TBA; tetrabutylammonium), were synthesized according to a typical one‐pot reaction of [RuCl₂(p‐cymene)]₂ with the corresponding anchoring ligands (where L = 4,4′‐dicarboxy‐2,2′‐bipyridine (dcbpy), 4,4′‐bis((E)‐carboxyvinyl)‐2,2′‐bipyridine (dcvbpy), 4,7‐dicarboxy‐1,10‐phenanthroline (dcphen), or 4,7‐bis((E)‐carboxyvinyl)‐1,10‐phenanthroline (dcvphen)). The new Ru(II) dyes, [Ru(L)(bsbpy)(NCS)₂][TBA] that incorporated vinyl spacer(s) into ancillary and/or anchoring ligand displayed red‐shifted bands over the overall UV/VIS region relative to the absorption spectra of N719 . A combination of bsbpy ancillary and dcphen anchoring ligand showed the best result for the overall power conversion efficiency (η); i.e., a DSSC fabricated with [Ru(dcphen)(bsbpy)(NCS)₂][TBA] exhibited a power conversion efficiency (η) of 2.98% (compare to N719 , 4.82%).     

Enantioselective Syntheses of Rigidiusculamides A and B: Revision of the Relative Stereochemistry of Rigidiusculamide A

The first enantioselective synthesis of cytotoxic natural products rigidiusculamides A (ent‐ 21 ) and B ( 8 ) has been achieved by two synthetic routes. The first one is convergent based on the common intermediate 11 , obtained through a high yielding SmI₂‐mediated Reformatsky‐type reaction. A highly diastereoselective one‐pot Dess–Martin periodinane‐mediated bis‐oxidation allowed the direct conversion of the diastereomeric mixture of 11 into rigidiusculamide B ( 8 ). Isolation of minor diastereomer 21 , in combination with computational work, allowed us to suggest the structure of the natural rigidiusculamide A to be 21 , as synthesized by the second route. Four diastereomers ( 7 , 7 , 22a , and 22b ) and an enantiomer ( 21 ) of rigidiusculamide A ( 21 ) have been synthesized. On the basis of literature precedents and computational work, a biosynthetic pathway for rigidiusculamides A and B was proposed to account for the opposite configuration at C‐5 of those two congeners.     

Synthesis and characterization of poly(arylene ether)s containing 6‐(4‐hydroxyphenyl)pyridazin‐3(2H)‐one or 6‐(4‐hydroxyphenyl)pyridazine moieties

A series of novel soluble pyridazinone‐ or pyridazine‐containing poly(arylene ether)s were prepared by a polycondensation reaction. The pyridazinone monomer, 6‐(4‐hydroxyphenyl)pyridazin‐3(2H)‐one ( 1 ), was synthesized from the corresponding acetophenone and glyoxylic acid in a simple one‐pot reaction. The pyridazinone monomer was successfully copolymerized with bisphenol A (BPA) or 1,2‐dihydro‐4‐(4‐hydroxyphenyl)phthalazin‐1(2H)‐one (DHPZ) and bis(4‐fluorophenyl)sulfone to form high‐molecular‐weight polymers. The copolymers had inherent viscosities of 0.5–0.9 dL/g. The glass‐transition temperatures (T_g's) of the copolymers synthesized with BPA increased with increasing content of the pyridazinone monomer. The T_g's of the copolymers synthesized from DHPZ with different pyridazinone contents were similar to those of the two homopolymers. The homopolymers showed T_g's from 202 to 291 °C by differential scanning calorimetry. The 5% weight loss temperatures in nitrogen measured by thermogravimetric analysis were in the range of 411–500 °C. 4‐(6‐Chloropyridazin‐3‐yl)phenol ( 2 ) was synthesized from 1 via a simple one‐pot reaction. 2 was copolymerized with 4,4′‐isopropylidenediphenol and bis(4‐fluorophenyl)sulfone to form high‐T_g polymers. The copolymers with less than 80 mol % pyridazinone or chloropyridazine monomers were soluble in chlorinated solvents such as chloroform. The copolymers with higher pyridazinone contents and homopolymers were not soluble in chlorinated solvents but were still soluble in dipolar aprotic solvents such as N‐methylpyrrolidinone. The soluble polymers could be cast into flexible films from solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3328–3335, 2006     

An Efficient Five‐Component Reaction for the Synthesis of 4,4′‐((2‐Oxoindoline‐3,3‐diyl)bis(methylene))bis(2‐aryl‐1H‐pyrrolo[3,4‐c]quinoline‐1,3(2H)‐dione) Derivatives

An efficient cascade process five‐component reaction of isatins and 3‐oxo‐N‐arylbutanamide for the synthesis of 4,4′‐((2‐oxoindoline‐3,3‐diyl)bis(methylene))bis(2‐aryl‐1H‐pyrrolo[3,4‐c]quinoline‐1,3(2H)‐dione) derivatives was reported under mild condition. The advantages of this strategy are easy to obtain raw materials, convenient one‐pot procedure, and simple operation.     

Synthesis,Characterization, and Antimicrobial Evolution of Bissydnone Based on Sulfonamide Derivatives

3,3′‐(Sulfonyldi‐1,4‐phenylene)bis(4‐substituted aminosulfonyl)sydnones ( 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j ) were synthesized from the starting material 4,4′‐diaminodiphenylsulfone. The synthesized compounds were characterized by IR, NMR, and elemental analysis. Some of the compounds were effectively active against Gram‐positive bacteria (Streptococcus pneumoniae and Staphylococcus aureus) and Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa).     

Uncatalyzed,One-pot Synthesis of 3,3'-(Benzylene)bis(4-hydroxy-2H-chromen-2-one)Derivatives under Thermal Solvent-free Conditions

A series of 3,3′‐(benzylene)bis(4‐hydroxy‐2H‐chromen‐2‐one) derivatives have been synthesized from condensation reactions of 4‐hydroxycoumarin with benzaldehydes under thermal solvent‐free conditions. This environmentally friendly synthesis is uncatalyzed and affords the desired products in excellent yields.     

Copolymers comprising 2,7-carbazole and bis-benzothiadiazole units for bulk-heterojunction solar cells

On the basis of theoretical considerations of the intramolecular charge transfer (ICT) effect, we have designed a series of donor (D)–acceptor (A) conjugated polymers based on bis‐benzothiadiazole (BBT). A PPP‐type copolymer of electron‐rich 2,7‐carbazole (CZ) and electron‐deficient BBT units poly[N‐(2‐decyltetradecyl)‐2,7‐carbazole‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazole)}] ( PCZ‐BBT ), a PPV‐type copolymer poly[N‐(2‐decyltetradecyl)‐2,7‐carbazolevinylene‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazolevinylene)}] ( PCZV‐BBTV ), and a tercopolymer based on carbazole, thiophene, and BBT poly[N‐(2‐decyltetradecyl)‐2,7‐(di‐2‐thienyl)carbazole‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazole)}] ( PDTCZ‐BBT ) have been synthesized to understand the influence of BBT acceptor structure and linkage on the photovoltaic characteristics of the resulting materials. Both the HOMO and LUMO of the resulting polymers are found to be deeper‐lying than those of benzothiadiazole‐based polymers. The measured electrochemical band gaps (eV) are in the following order: PDTCZ‐BBT (1.65 eV) < PCZV‐BBTV (1.69 eV) < PCZ‐BBT (1.75 eV). All the polymers provide a photovoltaic response when blended with a fullerene derivative as an electron acceptor. The best cell reaches a power conversion efficiency of 2.07 % estimated under standard solar light conditions (AM1.5G, 100 mW cm^?2). We demonstrate for the first time that BBT‐based polymers are promising materials for use in bulk‐heterojunction solar cells.     

Syntheses and electroluminescence properties of conjugated poly(p‐phenylene vinylene) derivatives bearing dendritic pendants

A series of new poly(p‐phenylene vinylene) derivatives with different dendritic pendants—poly{2‐[3′,5′‐bis(2″‐ethylhexyloxy)benzyloxy]‐1,4‐phenylenevinylene} (BE–PPV), poly{2‐[3′,5′‐bis(3″,7″‐dimethyl)octyloxy]‐1,4‐phenylenevinylene} (BD–PPV), poly(2‐{3′,5′‐bis[3″,5″‐bis(2?‐ethylhexyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene) (BBE–PPV), poly(2‐{3′,5′‐bis[3″,5″‐bis(3?,7?‐dimethyloctyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene) (BBD–PPV), and poly[(2‐{3′,5′‐bis[3″,5″‐bis(2?‐ethylhexyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene)‐co‐(2‐{3′,5′‐bis[3″,5″‐bis(3?,7?‐dimethyloctyloxy)benzyloxy]benzyloxy}‐1,4‐phenylenevinylene)] (BBE‐co‐BBD–PPV; 1:1)—were successfully synthesized according to the Gilch route. The structures and properties of the monomers and the resulting conjugated polymers were characterized with ¹H and ¹³C NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, ultraviolet–visible absorption spectroscopy, photoluminescence, and electroluminescence spectroscopy. The obtained polymers possessed excellent solubility in common solvents and good thermal stability, with a 5% weight loss temperature of more than 328 °C. The weight‐average molecular weights and polydispersity indices of BE–PPV, BD–PPV, BBE–PPV, BBD–PPV, and BBE‐co‐BBD–PPV (1:1) were in the range of 1.33–2.28 × 10⁵ and 1.35–1.53, respectively. Double‐layer light‐emitting diodes (LEDs) with the configuration of indium tin oxide/polymer/tris(8‐hydroxyquinoline) aluminum/Mg:Ag/Ag devices were fabricated, and they emitted green‐yellow light. The turn‐on voltages of BE–PPV, BD–PPV, BBE–PPV, BBD–PPV, and BBE‐co‐BBD–PPV (1:1) were approximately 5.6, 5.9, 5.5, 5.2, and 4.8 V, respectively. The LED devices of BE–PPV and BD–PPV possessed the highest electroluminescent performance; they exhibited maximum luminance with about 860 cd/m² at 12.8 V and 651 cd/m² at 13 V, respectively. The maximum luminescence efficiency of BE–PPV and BD–PPV was in the range of 0.37–0.40 cd/A. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3126–3140, 2005     

Synthesis of 5‐Aminotetrazole‐1 N‐oxide and Its Azo Derivative: A Key Step in the Development of New Energetic Materials

1‐Hydroxy‐5‐aminotetrazole ( 1 ), which is a long‐desired starting material for the synthesis of hundreds of new energetic materials, was synthesized for the first time by the reaction of aqueous hydroxylamine with cyanogen azide. The use of this unique precursor was demonstrated by the preparation of several energetic compounds with equal or higher performance than that of commonly used explosives, such as hexogen (RDX). The prepared compounds, including energetic salts of 1‐hydroxy‐5‐aminotetrazole (hydroxylammonium ( 2 , two polymorphs) and ammonium ( 3 )), azo‐coupled derivatives (potassium ( 5 ), hydroxylammonium ( 6 ), ammonium ( 7 ), and hydrazinium 5,5′‐azo‐bis(1‐N‐oxidotetrazolate ( 8 , two polymorphs)), as well as neutral compounds 5,5′‐azo‐bis(1‐oxidotetrazole) ( 4 ) and 5,5′‐bis(1‐oxidotetrazole)hydrazine ( 9 ), were intensively characterized by low‐temperature X‐ray diffraction, IR, Raman, and multinuclear NMR spectroscopy, elemental analysis, and DSC. The calculated energetic performance, by using the EXPLO5 code, based on the calculated (CBS‐4M) heats of formation and X‐ray densities confirm the high energetic performance of tetrazole‐N‐oxides as energetic materials. Last but not least, their sensitivity towards impact, friction, and electrostatic discharge were explored. 5,5′‐Azo‐bis(1‐N‐oxidotetrazole) deflagrates close to the DDT (deflagration‐to‐detonation transition) faster than all compounds that have been investigated in our research group to date.     

Three‐component synthesis of spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐triones in water

A one‐pot, three‐component method for the efficient and simple synthesis of novel 2′‐amino‐8′,9′‐dihydro‐3′H‐spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐2,4′,6′(7′H,10′H)‐trione derivatives in aqueous media is reported. J. Heterocyclic Chem., (2011).     

Synthesis and properties of soluble trifluoromethyl‐substituted polyimides containing laterally attached p‐Terphenyls

A new fluorinated diamine monomer, 2′,5′‐bis(4‐amino‐2‐trifluoromethylphenoxy)‐p‐terphenyl, was synthesized from the chloro‐displacement of 2‐chloro‐5‐nitrobenzotrifluoride with the potassium phenolate of 2,5‐diphenylhydroquinone, followed by hydrazine palladium‐catalyzed reduction. A series of trifluoromethyl‐substituted polyimides containing flexible ether linkages and laterally attached side rods were synthesized from the diamine with various aromatic dianhydrides via a conventional two‐step process. The inherent viscosities of the poly(amic acid) precursors were 0.84–1.26 dL/g. All the polyimides afforded flexible and tough films. The use of 4,4′‐oxydiphthalic anhydride and 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride produced essentially colorless polyimide films. Most of the polyimides revealed an excellent solubility in many organic solvents. The glass‐transition temperatures of these polyimides were recorded between 254 and 299 °C by differential scanning calorimetry, and the softening temperatures of the polymer films stayed in the range of 253–300 °C according to thermomechanical analysis. The polyimides did not show significant decomposition before 500 °C in air or under nitrogen. These polyimides also showed low dielectric constants (2.83–3.34 at 1 MHz) and low moisture absorption (0.4–2.2%). For a comparative study, a series of analogous polyimides based on the nonfluorinated diamine 2′,5′‐bis(4‐aminophenoxy)‐p‐terphenyl were also prepared and characterized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1255–1271, 2004     

Synthesis,characterization and solid‐phase extraction properties of novel bis(diazo‐azomethine) ligands supported on mesoporous silica

The novel mesoporous silica‐supported bis(diazo‐azomethine) compounds have been synthesized and characterized successively. In the first step, 1,3‐phenylenedimethanamine and 4,4′‐diaminodiphenylmethane were diazotized, and the obtained bis(diazonium) cations were coupled with 2,4‐dihydroxybenzaldehyde. The synthesized bis(diazo‐carbonyl) compounds, 5,5′‐((1,3‐phenylenebis(methylene))bis(diazene‐2,1‐diyl))bis(2,4‐dihydroxybenzaldehyde) (A1) and 5,5′‐((methylenebis(4,1‐phenylene))bis(diazene‐2,1‐diyl))bis(2,4‐dihydroxybenzaldehyde) (A2) were chemically supported on amino‐modified silica‐gel (as L1 and L2). Elemental analysis, liquid chromatography‐mass spectroscopy, liquid‐phase NMR (¹H and ¹³C) and solid‐phase NMR (CP‐MAS ²⁹Si and ¹³C), FT‐IR, TG/DTA, scanning electron microscopy and energy‐dispersive X‐ray spectroscopy techniques were used for characterizations of all the synthesized compounds. The syringe and batch techniques were applied for the solid‐phase extraction properties of Pb(II), Cu(II), Cd(II) and Cr(III) ions using an inductively coupled plasma‐atomic emission spectroscopy instrument. The recoveries of Pb(II), Cu(II), Cd(II) and Cr(III) ions have been achieved to 95–99% with the (RSDs) of ± 2–3% in optimum conditions.     

Ultrasound‐Promoted Catalyst‐Free Synthesis of 2,2′‐(1,4‐Phenylene)bis[1‐acetyl‐1,2‐dihydro‐4H‐3,1‐benzoxazin‐4‐one] Derivatives

A convenient approach to 2,2′‐(1,4‐phenylene)bis[1‐acetyl‐1,2‐dihydro‐4H‐3,1‐benzoxazin‐4‐one] derivatives 4 was explored employing the one‐pot condensation of anthranilic acids (=2‐aminobenzoic acids) 1 with terephthalaldehyde (=benzene‐1,4‐dicarboxaldehyde; 2 ) under ultrasound‐irradiation conditions (Scheme 1). The reactions proceeded smoothly in the presence of excess Ac₂O in the absence of any other catalyst and solvent to afford the respective products in high yields.     

Synthesis and properties of sulfonated polyimides from homologous sulfonated diamines bearing bis(aminophenoxyphenyl)sulfone

Three homologous sulfonated diamines bearing a bis(aminophenoxyphenyl)sulfone structure, namely, bis[4‐(4‐aminophenoxy)phenyl]sulfone‐3,3′‐disulfonic acid (pBAPPS‐3DS), bis[4‐(4‐aminophenoxy)phenyl]sulfone‐2,2′‐disulfonic acid (pBAPPS‐2DS), and bis[4‐(4‐aminophenoxy)‐2‐(3‐sulfobenzoyl)phenyl]sulfone (pBAPPS‐2DSB), were synthesized. A series of sulfonated polyimides (SPIs) were synthesized from 1,4,5,8‐naphthalene tetracarboxylic dianhydride, these sulfonated diamines, and nonsulfonated diamines, and their properties were investigated in comparison with those reported for the SPIs from another homologous diamine or bis[4‐(3‐aminophenoxy)phenyl]sulfone‐3,3′‐disulfonic acid (mBAPPS‐3DS). These SPIs were soluble in common aprotic solvents and showed reasonably high proton conductivity, except for pBAPPS‐2DS‐based SPIs, the conductivity of which was slightly lower because of the lower water uptake. The water stability of these SPIs considerably depended on the structure of the sulfonated diamines and was in the order of pBAPPS‐2DSB ≈ pBAPPS‐2DS > pBAPPS‐3DS ? mBAPPS‐3DS. Their water stability was much lower than that of the SPIs from 4,4′‐bis(4‐aminophenoxy)biphenyl‐3,3′‐disulfonic acid. The reason was discussed on the basis of the basicity of the sulfonated diamine and the solubility property of the SPIs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2797–2811, 2007     

Synthesis and properties of a bisphenol A based phthalonitrile resin

A multiple aromatic ether linked phthalonitrile was synthesized and characterized. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A with 4,4′‐difluorobenzophenone in the presence of K₂CO₃ as the base in an N,N‐dimethylformamide/toluene solvent mixture, followed by end capping with 4‐nitrophthalonitrile in a two‐step, one‐pot reaction. The monomer properties were compared to those of the known resin 2,2‐bis[4‐(3,4‐dicyanophenoxy)phenyl]propane after being cured in the presence of bis[4‐(4‐aminophenoxy)phenyl]sulfone. Rheometric measurements and thermogravimetric analysis showed that the oligomeric phthalonitrile resin maintained good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long‐term oxidative stability. The ether‐linked phthalonitrile resin absorbed less than 2.5% water by weight after exposure to an aqueous environment for extended periods. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4136–4143, 2005     

Diarylheptanoids from the Rhizomes of Alpinia officinarum

A novel dimeric diarylheptanoid, (5R,5′R)‐7,7′‐(6,6′‐dihydroxy‐5,5′‐dimethoxy[1,1′‐biphenyl]‐3,3′‐diyl)bis[5‐methoxy‐1‐phenylheptan‐3‐one] ( 1 ), and two new diarylheptanoids, (4E,6R)‐6‐hydroxy‐7‐(4‐hydroxy‐3‐methoxyphenyl)‐1‐phenylhept‐4‐en‐3‐one ( 2 ) and (4E,6R)‐6‐hydroxy‐1,7‐diphenylhept‐4‐en‐3‐one ( 3 ), together with seven known diarylheptanoids, were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by application of extensive spectroscopic analyses and the modified Mosher method.     

Efficient Synthesis of 2‐(2‐Aminophenyl)‐2,3‐dihydropyridin‐4(1H)‐ones Based on a Cyclization/Ring Cleavage Procedure

(Benzyloxycarbonyl)‐protected 3,4‐benzo‐7‐hydroxy‐2,9‐diazabicyclo[3.3.1]non‐7‐enes were prepared by one‐pot cyclizations of 1,3‐bis(silyl enol ethers) with quinazolines. Subsequent hydrogenation resulted in one‐pot deprotection and rearrangement to give 2‐(2‐aminophenyl)‐2,3‐dihydropyridin‐4(1H)‐ones.