Post-synthetic derivatization of graphitic carbon nitride with methanesulfonyl chloride: Synthesis, characterization and photocatalysis

Bulk graphitic carbon nitride (CN) was synthetized by heating of melamine at 550 degrees C, and the exfoliated CN (ExCN) was prepared by heating of CN at 500 degrees C. Sulfur-doped CN was synthesized by heating of thiourea (S-CN) and by a novel procedure based on the post-synthetic derivatization of CN with methanesulfonyl (CH3SO2-) chloride (Mes-CN and Mes-ExCN). The obtained nanomaterials were investigated by common characterization methods and their photocatalytic activity was tested by means of the decomposition of acetic orange 7 (AO7) under ultraviolet A (UVA) irradiation. The content of sulfur in the modified CN decreased in the sequence of Mes-ExCN > Mes-CN > S-CN. The absorption of light decreased in the opposite manner, but no influence on the band gap energies was observed. The methanesulfonyl (mesyl) groups connected to primary and secondary amine groups were confirmed by high resolution mass spectrometry (HRMS). The photocatalytic activity decreased in the sequence of Mes-ExCN > ExCN > CN approximate to Mes-CN > S-CN. The highest activity of Mes-ExCN and ExCN was explained by the highest amounts of adsorbed Acetic Orange 7 (AO7). In addition, in the case of Mes-ExCN, chloride ions incorporated in the CN lattice enhanced the photocatalytic activity as well.Web of Science102art. no. 19

Synthesis and Use of Transition Metal Complexes with Helical Ligands

Disertační práce popisuje vývoj asymetrické syntézy analogů helicenů obsahujících 2H-pyranový nebo 2,7-dihydrooxepinový motiv v jejich opticky čisté podobě. Tyto molekuly byly v rámci práce plně charakterizovány a využity v enantioselektivní katalýze s přechodnými kovy jako chirální ligandy, v organokatalýze jako katalyzátory a v heterogenní katalýze jako chirální modifikátory. Příprava těchto analogů [5]- a [6]helicenů je založena na diastereoselektivní [2+2+2] cykloisomerizaci centrálně chirálních triynů v přítomnosti komplexů přechodných kovů. Stereoselektivita cyklizace je řízena 1,3- allylovým pnutím. Tato metoda přípravy je velmi všestranná a umožňuje jednoduchý přístup k chirálním ligandům, organokatalyzátorům nebo modifikátorům v neracemické formě. Fosfitové helikální ligandy obsahující 2,7-dihydrooxepinové kruhy byly zkoumány v asymetrické allylové aminaci katalyzované komplexy jednomocného iridia, kdy bylo dosaženo až 82% enantiomerního nadbytku. 2H-pyranový analog helicenu obsahující motiv dimethylaminopyridinu byl studován jako katalyzátor kinetické resoluce racemických sulfoximinů. Byly zkoumány různě substituované deriváty helicenů a jejich analogů jako chirální modifikátory v asymetrické redukci ethylpyruvátu na ethyllaktát.The Thesis describes our successful endeavour to develop asymmetric synthesis of functionalized 2H-pyran or 2,7-dihydrooxepine helicene-like compounds in an optically pure form. These helicene surrogates were fully characterized and their use in enantioselective catalysis as chiral ligands, organocatalysts or chiral modifiers was explored. A general method for the preparation of optically pure [5]- and [6]heterohelicenes by asymmetric synthesis is based on highly diastereoselective [2+2+2] cycloisomerization of centrally chiral triynes mediated/catalyzed by transition metal complexes. Stereochemical outcome of the cyclization process is controlled by 1,3-allylic-type strain. This new methodology is highly versatile providing an easy access to chiral ligands, organocatalysts or modifiers in a nonracemic form. Optically pure 2,7-dihydrooxepine [5]helicene-like phosphite ligands were explored in enantioselective allylic amination under catalysis by iridium(I) complexes to reach up to 82% ee. An organocatalysts represented by the optically pure 2H-pyran [5]helicene-like DMAP analogue was synthesized and applied to kinetic resolution of racemic sulfoximines. Finally, various functionalized derivatives of helicenes and helicene-like compounds (azahelicenes, DMAP analogues, (thio)urea derivatives) were...Katedra anorganické chemieDepartment of Inorganic ChemistryPřírodovědecká fakultaFaculty of Scienc

Chiral induction in intramolecular rhodium-catalyzed [2+2+2] cycloadditions of optically active allene-ene/yne-allene substrates

Allene-yne-allene and allene-ene-allene N-tosyl-linked substrates with two chiral centres in the α-position of the allene moiety were satisfactorily prepared starting both from racemic and chiral propargylic alcohols. The Wilkinson's complex-catalyzed [2+2+2] cycloaddition reaction of these substrates was evaluated. In the case of enantiomerically pure bisallenes, perfect stereoselectivity was observed, giving a diastereomerically pure cycloadduct. The chirality of starting bisallene substrates can be completely transferred to the cycloadducts, representing an atom-economical and enantiospecific process for the construction of fused polycycles. However, when reacting an oxygen-linked allene-ene-allene substrate, the stereoselectivity decreased and two diastereoisomers were formed. A detailed characterization study of the resulting cycloadducts allows us to identify the enantioisomer generated in the cycloaddition

Six-membered ring systems: with O and/or S atoms

A large variety of publications have emerged in 2012 involving O- and S-6- membered ring systems. The increasing number of reviews and other communica- tions dedicated to natural and synthetic derivatives and their biological significance highlights the importance of these heterocycles. Reviews on natural products involve biosynthesis and isolation of enantiomeric derivatives h12AGE4802i, biosynthesis, isolation, synthesis, and biological studies on the pederin family h12NPR980i and xanthones obtained from fungi, lichens, and bacteria h12CR3717i and on the potential chemotherapeutic value of phyto- chemical products and plant extracts as antidiabetic h12NPR580i, antimicrobial, and resistance-modifying agents h12NPR1007i. A more specific review covers a structure–activity relationship of endoperoxides from marine origin and their antitry- panosomal activity h12OBC7197i. New synthetic routes to naturally occurring, biologically active pyran derivatives have been the object of several papers. Different approaches have been discussed for the total synthesis of tetrahydropyran-containing natural products (")-zampanolide h12CEJ16868, 12EJO4130, 12OL3408i, (")-aspergillides A and B h12H(85)587, 12H(85)1255, 12TA252i, (þ)-neopeltolide h12JOC2225, 12JOC9840, 12H(85) 1255i, or their macrolactone core h12OBC3689, 12OL2346i. The total synthesis of bistramide A h12CEJ7452i and (þ)-kalihinol A h12CC901i and the stereoselec- tive synthesis of a fragment of bryostatin h12S3077, 12TL6163i have also been sur- veyed. Other papers relate the total synthesis of naturally occurring carbocyclic and heterocyclic-fused pyran compounds, such as (")-dysiherbaine h12CC6295i, penos- tatin B h12OL244i, Greek tobacco lactonic products, and analogues h12TL4293i and on the structurally intriguing limonoids andhraxylocarpins A–E h12CEJ14342i. The stereocontrolled synthesis of fused tetrahydropyrans was used in the preparation of blepharocalyxin D h12AGE3901i. Polyphenolic heterocyclic compounds have also received great attention in 2012. The biological activities and the chemistry of prenylated caged xanthones h12PCB78i, the occurrence of sesquiterpene coumarins h12PR77i, and the medicinal properties of the xanthone mangiferin h12MRME412i have been reviewed. An overview on the asymmetric syntheses of flavanones and chromanones h12EJO449i, on the synthesis and reactivity of flavones h12T8523i and xanthones h12COC2818i, on the synthesis and biosynthesis of biocoumarins h12T2553i, and on the synthesis and applications of flavylium compounds h12CSR869i has been discussed. The most recent developments in the synthesis and applications of sultones, a very important class of sulfur compounds, were reported h12CR5339i. A review on xanthene-based fluorescent probes for sensing cations, anions, bio- logical species, and enzyme activity has described the spiro-ring-opening approach with a focus on the major mechanisms controlling their luminescence behavior h12CR1910i. The design and synthesis of other derivatives to be used as sensors of gold species h12CC11229i and other specific metal cations h12PC823i have also been described. Recent advances related to coumarin-derived fluorescent chemosen- sors for metal ions h12COC2690i and to monitoring in vitro analysis and cellular imaging of monoamine oxidase activity h12CC6833i have been discussed. The study of various organic chromophores allowed the synthesis of novel dica- tionic phloroglucinol-type bisflavylium pigments h12SL2053i, and the optical and spectroscopic properties of several synthetic 6-aryldibenzo[b,d]pyrylium salts were explored h12TL6433i. Discussion of specific reactions leading to O- and S-membered heterocyclic compounds covers intramolecular radical cyclization h12S2475i and asymmetric enamine and dienamine catalysis h12EJO865i, oxa-Michael h12CSR988i and dom- ino Knoevenagel–hetero-Diels–Alder (hDA) reactions h12T5693i, and the versatility in cycloadditions as well as nucleophilic reactions using o-quinones h12CSR1050i. The use of specific reagents relevant to this chapter includes molecular iodine h12CEJ5460, 12COS561i, samarium diiodide–water for selective reductive transfor- mations h12CC330i, o-quinone methides as versatile intermediates h12CEJ9160i, InCl3 as catalyst h12T8683i, and gold and platinum p-acid mediated insertion of alkynes into carbon–heteroatom s-bonds h12S3401i. The remainder of this chapter discusses the most studied transformations on O- and S-6-membered heterocycles

Novel asymmetric formylation of aromatic compounds: Enantioselective synthesis of formyl 7,8- dipropyltetrathia[7]helicenes

Asymmetric formylation of aromatic compounds is virtually unexplored. We report the synthesis and evaluation of a library including 20 new chiral formamides in the kinetic resolution of 7,8-dipropyltetrathia[7]helicene, affording the corresponding formyl- or diformylhelicenes in up to 73% ee, making enantiopure compounds available by recrystallisation. With the N,N-disubstituted formamides used in this study, the best enantioselectivity has been achieved with R1=iPr, R2=Me, R3=H, R4=1-naphthyl or its 1-pyrenyl equivalent

Helicene-based Salt and Its Application for Organic Molecular Electronics

In this work we have focused on the substitution of the imidazolium cation with [6]helicene. The hypothesis for the preparation of the imidazolium-helicene hybrid was based on improving the properties of helicene for surface immobilization, enhancing its solubility in more polar solvents and last but not least finding advanced applications for helicenes in the development of electronic devices. The earlier prepared 1-butyl-3-([6]helicen-2-ylmethyl)imidazolium bromide was investigated in this manner

Complexes with metals of Group 9 containing fragment [( C5Me4Cn F2n+1) M]

Katedra anorganické chemieDepartment of Inorganic ChemistryFaculty of SciencePřírodovědecká fakult

Potential-driven On/Off Switch Strategy for the Electrosynthesis of [7]Helicene-derived Polymers.

3-([7]H elicen-9-yl)-thiophene hybrid monomer was electrooxidized in acetonitrile by cyclic voltammetry with anodic potential limits of +1.5 V or +2.5 V, resulting in a conductive and non-conductive polymer, respectively. The electrochemical findings were supplemented by microscopy investigations; UV-Vis, fluorescence and vibrational spectroscopies, ellipsometry measurements and computational chemistry. The electrodeposited polymers could be used for the further development of materials applicable in organic electronics and sensing technologies

Synthesis and Characterization of Helicene-Based Imidazolium Salt

Helicenes are functional molecules with broad spectrum of applications in physical and (bio)chemical research and development. Today, we are focused on synthetic approaches for preparation of helicene derivatives and conjugates leading to novel compounds with unique properties. A helicene-based imidazolium salt was synthesized starting from 2-methyl[6]helicene which undergoes radical bromination providing 2-(bromomethyl)[6]helicene. The subsequent treatment with 1-butylimidazole leads to corresponding bromide salt. The product prepared was consequently fully characterized from chemico-physical point of view using NMR and X-ray analysis, various spectrometric approaches, especially fluorescence spectroscopy, and electrochemical tools as chronopotentiometry and voltammetry. Here we present the first evidence of ionic fluid (molten salt) based on helicene substitution

Synthesis and Use of Transition Metal Complexes with Helical Ligands

The Thesis describes our successful endeavour to develop asymmetric synthesis of functionalized 2H-pyran or 2,7-dihydrooxepine helicene-like compounds in an optically pure form. These helicene surrogates were fully characterized and their use in enantioselective catalysis as chiral ligands, organocatalysts or chiral modifiers was explored. A general method for the preparation of optically pure [5]- and [6]heterohelicenes by asymmetric synthesis is based on highly diastereoselective [2+2+2] cycloisomerization of centrally chiral triynes mediated/catalyzed by transition metal complexes. Stereochemical outcome of the cyclization process is controlled by 1,3-allylic-type strain. This new methodology is highly versatile providing an easy access to chiral ligands, organocatalysts or modifiers in a nonracemic form. Optically pure 2,7-dihydrooxepine [5]helicene-like phosphite ligands were explored in enantioselective allylic amination under catalysis by iridium(I) complexes to reach up to 82% ee. An organocatalysts represented by the optically pure 2H-pyran [5]helicene-like DMAP analogue was synthesized and applied to kinetic resolution of racemic sulfoximines. Finally, various functionalized derivatives of helicenes and helicene-like compounds (azahelicenes, DMAP analogues, (thio)urea derivatives) were..