Dehydro side coupling of substituted pentacene derivatives

1,2,3,4,8,9,10,11-Octaalkylpentacenes were synthesized in high yields from tetrahydropentacenes by the pentacene-DDQ adduct method in the presence of amine. Dehydro side-coupling reactions of pentacene derivatives proceeded to give the corresponding 6,6'-dipentacenyl derivatives in high yields in the presence of a catalytic amount of CSA and 0.5 equiv of DDQ. The structures of dehydro side-coupling products of substituted pentacenes were determined by NMR and X-ray analysis. The combination of acid and DDQ was necessary for the dehydro side coupling of substituted pentacenes.     

Synthesis and characterization of functionalized silicon phthalocyanines for fabrication of self-assembled monolayers

Novel octasubstituted phthalocyanine derivatives XYSiPc(OR)₈ (X=alkyl, Y=alkoxy, R=alkane or alkene) were synthesized by reaction of alkoxy-substituted diiminoisoindolines with XSiCl₃ followed by quenching with an alcohol YOH. Three synthetic routes for adding anchoring groups to the phthalocyanines were explored: variation of the axial groups X and Y, or incorporation of vinyl groups around the periphery of the phthalocyanine ring. The latter approach yielded silicon and copper phthalocyanines with eight terminal vinyl groups, which reacted cleanly with thioacetic acid/AIBN to give products with eight protected terminal thiols.     

High‐Yield Synthesis of Amido‐Functionalized Polyoctahedral Oligomeric Silsesquioxanes by Using Acyl Chlorides

Homosubstituted amido‐functionalized polyoctahedral oligomeric silsesquioxanes (POSS) have been synthesized by using acyl chlorides in high yields (ca. 95 %). The method proved to be superior over “conventional” syntheses applying carboxylic acids or acid anhydrides, which are much less efficient (ca. 60 % yield). A palette of aryl and alkyl groups has been used as side‐chains. The structures of the resulting amide‐POSS are supported by multinuclear ¹H, ¹³C, ²⁹Si NMR and FTIR spectroscopy and their full conversion into octasubstituted derivatives was confirmed using mass spectrometry. We also demonstrate that the functionalized silsesquioxanes with bulky organic side‐chains attached to cubic siloxane core form spherical‐like, well‐separated nanoparticles with a size of approximately 5 nm.     

Homologation method for preparation of substituted pentacenes and naphthacenes

Multi-substituted pentacenes, such as 1,2,3,4,6,8,9,10,11,13-decasubstituted pentacenes (Type I), 1,2,3,4,6,13-hexasubstituted pentacenes (Type II), 1,2,3,4-tetrasubstituted pentacenes (Type III), and 2,3-disubstituted pentacenes (Type IV), 1,2,3,4,6,11-hexasubstituted naphthacenes (Type V), 1,2,3,4-tetrasubstituted naphthacenes (Type VI), and 2,3-disubstituted naphthacenes (Type VII), were prepared by a homologation method. The homologation method involved the conversion of phthalic acid ester derivatives to two ring extended phthalic acid ester derivatives via diynes and metallacyclopentadienes using transition metals, such as Zr and Rh. For the formation of pentacenes of Type III and Type IV and naphthacenes of Type VII, trimethylsilyl-substituted diynes were used for zirconocene-mediated cyclization. Elimination of the trimethylsilyl groups after the cyclization afforded nonsubstituted position on pentacenes or naphthacenes. Structures of 1,4,6,8,9,10,11,13-octaethyl-2,3-bis(methoxycarbonyl)pentacene (9a) and 8,9,10,11-tetraethyl-2,3-bis(methoxycarbonyl)-1,4,6,13-tetrapropylpentacene (9b) were determined by X-ray analysis. The structure of 9a had the herringbone packing system in the crystal like nonsubstituted pentacene. However, 9b, whose substituents at 1,4,6,13-positions were changed from Et to Pr at 1,4,6,13-positions of 9a, had the face parallel plane system in the crystal.     

Exploring Crystal Structure in Ethyne‐Substituted Pentacenes,and Their Elaboration into Crystalline Dehydro[18]annulenes

Approaches to control the self‐assembly of aromatic structures to enhance intermolecular electronic coupling are the key to the development of new electronic and photonic materials. Acenes in particular have proven simple to functionalize to induce strong π‐stacking interactions, although finer control of intermolecular π‐overlap has proven more difficult to accomplish. In this report, we describe how very weak hydrogen bonding interactions can exert profound impact on solid‐state order in solubilized pentacenes, inducing self‐assembly in either head‐to‐tail motifs with strong 2‐D π‐stacking, or head‐to‐head orientations with much weaker, 1‐D π‐stacking arrangements. In order to achieve 3‐D π‐stacking useful for photovoltaic applications, we elaborated a series of diethynyl pentacenes to their trimeric dehydro[18]annulene forms. These large, strongly interacting structures did indeed behave as acceptors in polymer photovoltaic devices.     

Synthesis of 1,2,3,4,8,9,10,11-octahydro-[1,4] diazepino[6,5,4-jk ]earbazole and related compounds

1,2,3,4,8,9,10,11-Octahydro[1,4]diazepino[6,5,4-jk]earbazole (VIa) was synthesized from 2,3,4,5-tetrahydro-1H-benzodiazepine (la) via the route shown in Scheme 1. Other compounds which were prepared similarly are 3-acetyl-6-chloro-1,2,3,4,8,9,10,11-octahydro[1,4]diazepino-[6,5,4-jk]carbazole(Vb) and 3-methyl-1,2,3,4,8,9,10,11-octahydro[1,4]diazepino[6,5,4-jk]carb-azole (VIII). Chemical transformations which were carried out with VI and 3-acetyl-1,2,3,4,8,9, 10,11-octahydro[1,4]diazepino[6,5,4-jk]carbazole (Va) are also described.     

Double Homologation Method for Substituted Soluble Pentacenes and Dimerization Behaviours of Pentacenes

Double up : A zirconium‐mediated double homologation method was successfully applied for the synthesis of multi‐substituted pentacene derivatives from 1,2,4,5‐tetrakis(propargyl)benzenes. The bis(zirconacyclopentadiene) intermediates were also characterized. Among these symmetrical derivatives, tetra‐ and octa‐substituted pentacenes undergo reversible conversion between monomeric and dimeric forms.

     

Synthesis of Nitrido(phthalocyaninato)metal(V) Complexes RnPcMN (M = Re,Mo, W) and New Compounds with Nitrido‐Bridges between Rhenium and Elements of the Third Main Group

New tetra‐ and octasubstituted nitrido(phthalocyaninato)metal(V) complexes R_nPcMN (M = Re, Mo, W) were synthesized to obtain soluble nitrido‐bridged phthalocyanines. Phthalocyanines with nitrido bridges between rhenium and boron, aluminium, gallium and indium, respectively, were synthesized from nitrido(tetra‐tert.‐butylphthalocyaninato)rhenium(V) complex, tBu₄PcReN and suitable electrophilic reagents like BCl₃, B(C₆F₅)₃, BPh₃, BEt₃, AlCl₃, GaCl₃, GaBr₃, InCl₃, etc. The nitrido‐bridged compounds prepared show different stabilities depending on the substituents at the boron atom. Additionally, the possibility to increase the nucleophilicity of (C₅H₁₁)₈PcWN by reducing this complex with C₈K was studied. The reaction of the reduced complex with electrophiles, e.g. with tBuMeSiCl, Ph₃SiCl and Me₃GeCl indicates the formation of nitrogen‐bridged complexes.     

Comparative use of solvent‐free KF‐A12O3 and K2CO3 in acetone in the synthesis of quinoxaline 1,4‐dioxide derivatives designed as antimalarial drug candidates

In this paper we describe two new basic conditions for the synthesis of quinoxaline 1,4‐dioxide derivatives in moderate to good yields. These conditions, exemplified by the use of K₂C0₃ in acetone or KF/A1₂0₃ in the absence of an organic solvent, were reproducible and applicable to the synthesis of 2‐(carboethoxy)‐3‐phenylquinoxaline 1,4‐dioxide derivatives substituted in position 4 with electron‐donating or electron‐withdrawing groups.     

1,2,3,4‐Tetrasubstituted Cyclopentadienes and Their Applications for Metallocenes: Efficient Synthesis through Zirconocene‐ and CuCl‐Mediated Intermolecular Coupling of Two Alkynes and One Diiodomethane

1,2,3,4‐Tetrasubstituted cyclopentadienes and indene derivatives with identical or different substituents were obtained in good to excellent isolated yields through a zirconocene‐ and CuCl‐mediated intermolecular coupling process. This synthetic procedure involved three organic partners, including one CH₂I₂, and two different or identical alkynes. Two alkynes or one diyne undergo Cp₂Zr^II‐mediated (Cp=η⁵‐C₅H₅) pair‐selective reductive coupling to afford the corresponding zirconacyclopentadiene derivatives, which react, in the presence of CuCl and 1,3‐dimethyl‐3,4,5,6‐tetrahydro‐2(1 H)‐pyrimidinone (DMPU), with CH₂I₂ through intermolecular followed by intramolecular coupling to afford the cyclopentadiene derivatives. An application of the prepared tetrasubstituted cyclopentadiene derivatives was demonstrated by the facile synthesis of the corresponding zirconocene complexes [(^4RCp)₂ZrCl₂] and [(^4RCp)₂ZrR′₂] (R′=Me, Et, or nBu). The unique 1,2,3,4‐tetrasubstituted cyclopentadiene ligands and the corresponding metallocenes are expected to have further applications in organometallic chemistry and organic synthesis.     

Regioselective synthesis and biological activity of oxidized chitosan derivatives

Oxidized chitosan derivatives with various degrees of oxidation (DS, 0.1–1.0) were prepared by the treatment of chitosan with CrO₃/aq HClO₄ or by the oxidation of ­3‐O‐ and N‐protected chitosan with 30% aq H₂O₂/Na₂WO₄ followed by 3‐O‐ and N‐deprotection. The oxidized products were then N‐acetylated with Ac₂O in order to improve their water‐solubility. Although the oxidized chitosan derivative of DS 0.28 and the degree of N‐acetylation of chitosan (DA) 38% was insoluble in the pH 3–8 region, that of DS 0.26 and DA 76% was soluble in the neutral pH range. The newly‐prepared acetylated and oxidized chitosan derivatives were found to suppress the chemiluminescence response of inflammatory cells such as canine polymorphonuclear cells (PMNs). Analysis by the surface plasmon resonance method revealed that the bind and release behavior of PMNs to acetylated oxidized chitosan derivatives was similar to that against carboxymethylated chitosan derivatives. The amount of water‐soluble chitosan derivative bound to cytokine IL‐8 was found to be affected by the structural and electronic features of the chitosan substituents in the chitosan chain. Copyright © 2003 John Wiley & Sons, Ltd.     

Liquid‐Crystalline Mixed [5 : 1]Hexa‐adducts of [60]Fullerene. Preliminary Communication

A liquid‐crystalline mixed [5 : 1]hexa‐adduct of [60]fullerene was synthesized by addition of two different malonate derivatives onto C₆₀. The hexa‐adduct derivative 2 was prepared by a stepwise synthetic procedure (fullerene→mono‐adduct of C₆₀→hexa‐adduct of C₆₀). Cyanobiphenyl and octyloxybiphenyl derivatives were selected as mesogens. The malonate derivatives showed either a monotropic nematic phase or a monotropic smectic A phase, and the hexa‐adduct derivative gave rise to an enantiotropic smectic A phase.     

Synthesis of 10‐amino‐9‐aryl‐2,3,4,5,6,7,9,10‐octahydroacridine‐1,8‐dione derivatives

A series of novel 10‐amino‐9‐aryl‐2,3,4,5,6,7,9,10‐octahydroacridine‐1,8‐dione derivatives 4 were synthesized by hydrazine or phenylhydrazine and 9‐aryl‐1,8‐dioxo‐2,3,4,5,6,7,9‐heptahydroxanthene derivatives 3 , which were prepared by 5‐substituted‐1,3‐cyclohexanedione 1 and aromatic aldehydes 2 in the presence of concentrated H₂SO₄ as a catalyst in water. The structures of all compounds were characterized by IR, MS, ¹H‐NMR, and elemental analysis, and the title compounds possess good fluorescence properties. J. Heterocyclic Chem., (2012).     

Efficient Syntheses of Novel Fluoro‐Substituted Pentacenes and Azapentacenes: Molecular and Solid‐State Properties

Non‐symmetrical 6,13‐disubstituted pentacenes bearing trifluoromethyl and aryl substituents have been synthesized starting from pentacenequinone. Diazapentacenes with a variety of fluorine substituents were prepared either via a Hartwig–Buchwald aryl amination route or by a S_NAr strategy. As a result of a non‐symmetric substitution pattern containing electron‐donating substituents in combination with electron‐accepting fluorine substituents, the synthesized compounds feature distinct molecular dipoles. All compounds are analyzed regarding their optoelectronic properties in solution with special focus on the frontier orbital energies as well as their molecular packing in the crystal structures. The analyses of isolated molecules are complemented by thin‐film studies to examine their solid‐state properties. A precise comparison between these and the molecular properties gave detailed insights into the exciton binding energies of these compounds, which are explained by means of a simple model considering the molecular packing and polarizabilities.     

Cyclopentannulated Dihydrotetraazapentacenes

The transition-metal-catalyzed cyclization of bissilylethynylated N,N’-dihydrotetraazapentacene (TIPS-TAP-H₂) into bissilylated cyclopenta[fg,qr]pentacenes is reported. Depending on the catalyst either none, one or two silyl groups migrate and change their positions in the formed five-membered rings. The optoelectronic properties are quite similar, whereas the packing motifs differ dramatically. Control experiments and quantum chemical calculations were performed to investigate the mechanism of the reaction and the selectivity of the silyl shift.     

Michael-Addition Reaction of Malononitrile with α,β-Unsaturated Cycloketones Catalyzed by KF／Al2O3

A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis.     

Lewis Acid‐Assisted Ene Cyclization of 2‐Azetidinone‐Tethered Enals: Synthesis of Enantiopure Carbacepham Derivatives

Diastereocontrolled Lewis acid‐catalyzed preparation of enantiopure carbacepham derivatives have been developed starting from 2‐azetidinone‐tethered enals. The BF₃?Et₂O‐promoted reaction of alkenylaldehydes 1 and 16 is effective as carbocyclization protocol to afford 4‐substituted 5‐hydroxycarbacephams or 3‐substituted 4,5‐dihydroxycarbacephams, respectively, by a type I carbonyl‐ene reaction, while the BF₃?Et₂O or SnCl₄‐mediated type II carbonyl‐ene cyclization of alkenylaldehydes 2 furnishes 3‐methylene 5‐hydroxycarbacephams along with the corresponding 3‐halo 5‐hydroxycarbacepham. The stereochemical outcome of these carbonyl‐ene cyclizations leading to carbacepham derivatives can be explained in terms of six‐membered, cyclic chair‐like transition‐state models. The formation of halocarbacepham derivatives is proposed to proceed by a stepwise mechanism.     

Fluorescence of New o‐Carborane Compounds with Different Fluorophores: Can it be Tuned?

Two sets of o‐carborane derivatives incorporating fluorene and anthracene fragments as fluorophore groups have been successfully synthesized and characterized, and their photophysical properties studied. The first set, comprising fluorene‐containing carboranes 6 – 9 , was prepared by catalyzed hydrosilylation reactions of ethynylfluorene with appropriate carboranylsilanes. The compound 1‐[(9,9‐dioctyl‐fluorene‐2‐yl)ethynyl]carborane ( 11 ) was synthesized by the reaction of 9,9‐dioctyl‐2‐ethynylfluorene and decaborane (B₁₀H₁₄). Furthermore, reactions of the lithium salt of 11 with 1 equivalent of 4‐(chloromethyl)styrene or 9‐(chloromethyl)anthracene yielded compounds 12 and 13 . Members of the second set of derivatives, comprising anthracene‐containing carboranes, were synthesized by reactions of monolithium or dilithium salts of 1‐Me‐1,2‐C₂B₁₀H₁₁, 1‐Ph‐1,2‐C₂B₁₀H₁₁, and 1,2‐C₂B₁₀H₁₂ with 1 or 2 equivalents of 9‐(chloromethyl)anthracene, respectively, to produce compounds 14 – 16 . In addition, 2 equivalents of the monolithium salts of 1‐Me‐1,2‐C₂B₁₀H₁₁ (Me‐o‐carborane) and 1‐Ph‐1,2‐C₂B₁₀H₁₁ (Ph‐o‐carborane) were reacted with 9,10‐bis(chloromethyl)anthracene to produce compounds 17 and 18 , respectively. Fluorene derivatives 6 – 9 exhibit moderate fluorescence quantum yields (32–44 %), whereas 11 – 13 , in which the fluorophore is bonded to the C_cluster (C_c), show very low emission intensity (6 %) or complete fluorescence quenching. The anthracenyl derivatives containing the Me‐o‐carborane moiety exhibit notably high fluorescence emissions, with ?_F=82 and 94 %, whereas their Ph‐o‐carborane analogues are not fluorescent at all. For these compounds, we have observed a correlation between the C_c?C_c bond length and the fluorescence intensity in CH₂Cl₂ solution, comparable to that observed for previously reported styrene‐containing carboranes. Thus, our hypothesis is that for systems of this type the fluorescence may be tuned and even predicted by changing the substituent on the adjacent C_c.     

Synthesis and Structure of 2‐Substituted Thieno[3′,2′:5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐one Derivatives

A series of new 2‐substituted 3‐(4‐chlorophenyl)‐5,8,9‐trimethylthieno[3′,2′: 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐ones 8 were synthesized via an aza‐Wittig reaction. Phosphoranylideneamino derivatives 6a or 6b reacted with 4‐chlorophenyl isocyanate to give carbodiimide derivatives 7a or 7b , respectively, which were further treated with amines or phenols to give compounds 8 in the presence of a catalytic amount of EtONa or K₂CO₃. The structure of 2‐(4‐chlorophenoxy)‐3‐(4‐chlorophenyl)‐5,8,9‐trimethylthieno[3′,2′: 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐one ( 8j ) was comfirmed by X‐ray analysis.     

Synthesis of New Fused and Spiro Heterocyclic Systems from 3,5‐Pyrazolidinediones

4‐Bromo‐1‐phenyl‐3,5‐pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4‐substituted derivatives 3–8 . The cyclized compounds 9–11 were achieved on refluxing compounds 3 , 4 or 6_a in glacial acetic acid or diphenyl ether. 4,4‐Dibromo‐1‐phenyl‐3,5‐pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5‐pyrazolidinediones 13–15 , respectively. The 4‐aralkylidine derivatives 16_a‐c , were subjected to Mannich reaction to give Mannich bases 17_a‐c‐22_a‐c , respectively. 4‐(p‐Methylphenylaminomethylidine)‐1‐phenyl‐3,5‐pyrazolidinedione 23 or 4‐(p‐methylphenylazo)‐1‐phenyl‐3,5‐pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S‐acetals to give pyrano[2,3‐c]pyrazole, pyrazolo[4′,3′:5,6]pyrano[2,3‐c]pyrazole, spiropyrazole‐4,3′‐pyrazole and spiropyrazole‐4,3′‐[1,2,4]triazolane derivatives 24–34 , respectively.