A Novel and Efficient Synthesis of 3‐[(4,5‐Dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐chromen‐2‐ones (=3‐[(4,5‐Dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐1‐benzopyran‐2‐ones)

An efficient one‐pot synthesis of 3‐[(4,5‐dihydro‐1H‐pyrrol‐3‐yl)carbonyl]‐2H‐chromen‐2‐one (=3‐[(4,5‐dihydro‐1H‐pyrrol‐3yl)carbonyl]‐2H‐1‐benzopyran‐2‐one) derivatives 4 by a four‐component reaction of a salicylaldehyde 1 , 4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one, a benzylamine 2 , and a diaroylacetylene (=1,4‐diarylbut‐2‐yne‐1,4‐dione) 3 in EtOH is reported. This new protocol has the advantages of high yields (Table), and convenient operation. The structures of these coumarin (=2H‐1‐benzopyran‐2‐one) derivatives, which are important compounds in organic chemistry, were confirmed spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this reaction is proposed (Scheme 2).     

Synthesis of (4Z)‐4‐(Arylmethylidene)‐5‐ethoxy‐1,3‐oxazolidine‐2‐thiones by the Reaction of Ethyl (2Z)‐3‐Aryl‐2‐isothiocyanatoprop‐2‐enoates with Organolithium Compounds

A convenient one‐pot method for the preparation of (4Z)‐4‐(arylmethylidene)‐5‐ethoxy‐1,3‐oxazolidine‐2‐thiones 2 and 3 from ethyl (2Z)‐3‐aryl‐2‐isothiocyanatoprop‐2‐enoates 1 , which can be easily prepared from ethyl 2‐azidoacetate and aromatic aldehydes, has been developed. Thus, these α‐isothiocyanato α,β‐unsaturated esters were treated with organolithium compounds, including lithium enolates of acetates, to provide 5‐substituted (4Z)‐4‐(arylmethylidene)‐5‐ethoxy‐1,3‐oxazolidine‐2‐thiones, 2 , and 2‐[(4Z)‐(4‐arylmethylidene)‐5‐ethoxy‐2‐thioxo‐1,3‐oxazolidin‐5‐yl]acetates, 3 .     

Synthesis and Fungicidal Activity of (E)‐5‐[1‐(2‐Oxo‐1‐oxaspiro[4,5]dec/non‐3‐en‐3‐yl)ethylidene]‐2‐aminoimidazolin‐4‐one Derivatives

The novel fungicidal agents, (E )‐5‐[1‐(2‐oxo‐1‐oxaspiro[4,5]dec/non‐3‐en‐3‐yl)ethylidene]‐2‐aminoimidazolin‐ 4‐one derivatives, were designed and synthesized in moderate to excellent yields in four steps using α ‐hydroxyketone and diketene as raw materials and characterized by HR‐ESI‐MS , ¹H NMR and X‐ray diffraction. The preliminary bioassay showed that some of these compounds, such as 5e , 6a , 6e , and 7 h exhibit 87.8%, 91.3%, 89.9% and 87.8% inhibition rates against Sclerotinia scleotiorum , 3b , 3c , 4c and 7 h exhibit 96.4%, 92.5%, 90.3% and 76.9% inhibition rates against Phytophthora capsici at the concentration of 50 µg/mL , respectively. These compounds exhibited significant fungicidal activities against S. scleotiorum and P. capsici with EC₅₀ values of 2.56–11.60 µg/mL , and compounds 6e and 7 h exhibited weak inhibition against the spore germination of S. scleotiorum , while the spore germination of P. capsici was strongly inhibited by compound 7 h solution. Scanning electron microscopy (SEM ) and transmission electron microscopy (TEM ) observation indicated that compound 7 h had a significant impact on the structure and function of the hyphal cell wall of P. capsici mycelium.     

One‐Pot Synthesis of 4‐(Alkylamino)‐1‐(arylsulfonyl)‐3‐benzoyl‐1,5‐ dihydro‐5‐hydroxy‐5‐phenyl‐2H‐pyrrol‐2‐ones via a Multicomponent Reaction

An effective route to novel 4‐(alkylamino)‐1‐(arylsulfonyl)‐3‐benzoyl‐1,5‐dihydro‐5‐hydroxy‐5‐phenyl‐2H‐pyrrol‐2‐ones 10 is described (Scheme 2). This involves the reaction of an enamine, derived from the addition of a primary amine 5 to 1,4‐diphenylbut‐2‐yne‐1,4‐dione, with an arenesulfonyl isocyanate 7 . Some of these pyrrolones 10 exhibit a dynamic NMR behavior in solution because of restricted rotation around the C? N bond resulting from conjugation of the side‐chain N‐atom with the adjacent α,β‐unsaturated ketone group, and two rotamers are in equilibrium with each other in solution ( 10 ? 11 ; Scheme 3). The structures of the highly functionalized compounds 10 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS), by elemental analyses, and, in the case of 10a , by X‐ray crystallography. A plausible mechanism for the reaction is proposed (Scheme 4).     

Synthesis and Conformational Analysis of 1′‐ and 3′‐Substituted 2‐Deoxy‐2‐fluoro‐D‐ribofuranosyl Nucleosides

Convergent syntheses of the 9‐(3‐X‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranosyl)adenines 5 (X=N₃) and 7 (X=NH₂), as well as of their respective α‐anomers 6 and 8 , are described, using methyl 2‐azido‐5‐O‐benzoyl‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranoside ( 4 ) as glycosylating agent. Methyl 5‐O‐benzoyl‐2,3‐dideoxy‐2,3‐difluoro‐β‐D ‐ribofuranoside ( 12 ) was prepared starting from two precursors, and coupled with silylated N⁶‐benzoyladenine to afford, after deprotection, 2′,3′‐dideoxy‐2′,3′‐difluoroadenosine ( 13 ). Condensation of 1‐O‐acetyl‐3,5‐di‐O‐benzoyl‐2‐deoxy‐2‐fluoro‐β‐D ‐ribofuranose ( 14 ) with silylated N²‐palmitoylguanine gave, after chromatographic separation and deacylation, the N⁷‐β‐anomer 17 as the main product, along with 2′‐deoxy‐2′‐fluoroguanosine ( 15 ) and its N⁹‐α‐anomer 16 in a ratio of ca. 42 : 24 : 10. An in‐depth conformational analysis of a number of 2,3‐dideoxy‐2‐fluoro‐3‐X‐D ‐ribofuranosides (X=F, N₃, NH₂, H) as well as of purine and pyrimidine 2‐deoxy‐2‐fluoro‐D ‐ribofuranosyl nucleosides was performed using the PSEUROT (version 6.3) software in combination with NMR studies.     

A Convenient Synthesis of 2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH

2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with ⁱPr₂NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO₂ to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH?n H₂O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano[2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano[3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.     

Report on an Unusual Cascade Reaction between Azulenes and 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐Dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ)

The oxidation of 1‐(3,8‐dimethylazulen‐1‐yl)alkan‐1‐ones 1 with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (=4,5‐dichloro‐3,6‐dioxocyclohexa‐1,4‐diene‐1,2‐dicarbonitrile; DDQ) in acetone/H₂O mixtures at room temperature does not only lead to the corresponding azulene‐1‐carboxaldehydes 2 but also, in small amounts, to three further products (Tables 1 and 2). The structures of the additional products 3 – 5 were solved spectroscopically, and that of 3a also by an X‐ray crystal‐structure analysis (Fig. 1). It is demonstrated that the bis(azulenylmethyl)‐substituted DDQ derivatives 5 yield on methanolysis or hydrolysis precursors, which in a cascade of reactions rearrange under loss of HCl into the pentacyclic compounds 3 (Schemes 4 and 7). The found 1,1′‐[carbonylbis(8‐methylazulene‐3,1‐diyl)]bis[ethanones] 4 are the result of further oxidation of the azulene‐1‐carboxaldehydes 2 to the corresponding azulene‐1‐carboxylic acids (Schemes 9 and 10).     

Synthesis and Characterization of Enantiomerically Pure cis‐ and trans‐3‐Fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphadecalin 3‐Oxides as γ‐Homoacetylcholine Mimetics and Inhibitors of Acetylcholinesterase

The title compounds, the P(3)‐axially and P(3)‐equatorially substituted cis‐ and trans‐configured 8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphadecalin 3‐oxides (=8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphabicyclo[4.4.0]decane 3‐oxides=2‐fluorohexahydro‐6‐(phenylmethyl)‐4H‐1,3,2‐dioxaphosphorino[5,4‐c]pyridine 2‐oxides) were prepared (ee>98%) and fully characterized (Schemes 2 and 3). The absolute configurations were established from that of their precursors, the enantiomerically pure cis‐ and trans‐1‐benzyl‐4‐hydroxypiperidine‐3‐methanols which were unambiguously assigned. Being configuratively fixed and conformationally constrained phosphorus analogues of acetyl γ‐homocholine (=3‐(acetyloxy)‐N,N,N‐trimethylpropan‐1‐aminium), they are suitable probes for the investigation of molecular interactions with acetylcholinesterase. As determined by kinetic methods, all of the compounds are weak inhibitors of the enzyme.     

Hydriodic Acid‐Mediated Cyclization of α‐Substituted Secondary 2‐Ethenylbenzamides: Synthesis of 2‐Substituted 2,3‐Dihydro‐3,3‐dimethyl‐1H‐isoindol‐1‐ones and 3,3‐Disubstituted (E)‐1‐(Arylimino)‐1,3‐dihydroisobenzofurans

A new and facile method for the preparation of 2‐substituted 2,3‐dihydro‐3,3‐dimethyl‐1H‐isoindol‐1‐ones 3 and 3,3‐disubstituted (E)‐1‐(arylimino)‐1,3‐dihydroisobenzofurans 6 has been developed. Thus, treatment of N‐alkyl(or aryl)‐2‐(1‐methylethen‐1‐yl)benzamides 2 with concentrated hydriodic acid (HI) in MeCN at room temperature afforded 3 . Similar treatment of N‐aryl‐2‐(1‐phenylethen‐1‐yl)benzamide 5 with concentrated HI at 0° afforded 6 .     

Alternative Synthesis of 2‐Hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one

The 2‐hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one ( 1 ) was synthesized in 42% yield by rearrangement of epoxy ketone 10 on treatment with BF₃⋅Et₂O under anhydrous conditions. Intermediate 10 was available from the known enone 8 , either via direct epoxidation (60% H₂O₂, NaOH, MeOH; yield 50%), or via reduction to the corresponding allylic alcohol 14 (LiAlH₄, THF), followed by epoxidation ([VO(acac)₂], ^tBuOOH) and reoxidation under Swern conditions, in 37% total yield.     

Effective Methods for the Synthesis of N‐Methyl β‐Amino Acids from All Twenty Common α‐Amino Acids Using 1,3‐Oxazolidin‐5‐ones and 1,3‐Oxazinan‐6‐ones

N‐Methyl β‐amino acids are generally required for application in the synthesis of potentially bioactive modified peptides and other oligomers. Previous work highlighted the reductive cleavage of 1,3‐oxazolidin‐5‐ones to synthesise N‐methyl α‐amino acids. Starting from α‐amino acids, two approaches were used to prepare the corresponding N‐methyl β‐amino acids. First, α‐amino acids were converted to N‐methyl α‐amino acids by the so‐called ‘1,3‐oxazolidin‐5‐one strategy’, and these were then homologated by the Arndt–Eistert procedure to afford N‐protected N‐methyl β‐amino acids derived from the 20 common α‐amino acids. These compounds were prepared in yields of 23–57% (relative to N‐methyl α‐amino acid). In a second approach, twelve N‐protected α‐amino acids could be directly homologated by the Arndt–Eistert procedure, and the resulting β‐amino acids were converted to the 1,3‐oxazinan‐6‐ones in 30–45% yield. Finally, reductive cleavage afforded the desired N‐methyl β‐amino acids in 41–63% yield. One sterically congested β‐amino acid, 3‐methyl‐3‐aminobutanoic acid, did give a high yield (95%) of the 1,3‐oxazinan‐6‐one ( 65 ), and subsequent reductive cleavage gave the corresponding AIBN‐derived N‐methyl β‐amino acid 61 in 71% yield (Scheme 2). Thus, our protocols allow the ready preparation of all N‐methyl β‐amino acids derived from the 20 proteinogenic α‐amino acids.     

A Novel Route to 1‐Substituted 3‐(Dialkylamino)‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles

Heptalenecarbaldehydes 1 / 1′ as well as aromatic aldehydes react with 3‐(dicyanomethylidene)‐indan‐1‐one in boiling EtOH and in the presence of secondary amines to yield 3‐(dialkylamino)‐1,2‐dihydro‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles (Schemes 2 and 4, and Fig. 1). The 1,2‐dihydro forms can be dehydrogenated easily with KMnO₄ in acetone at 0° (Scheme 3) or chloranil (=2,3,5,6‐tetrachlorocyclohexa‐2,5‐diene‐1,4‐dione) in a ‘one‐pot’ reaction in dioxane at ambient temperature (Table 1). The structures of the indeno[2,1‐c]pyridine‐4‐carbonitriles 5′ and 6a have been verified by X‐ray crystal‐structure analyses (Fig. 2 and 4). The inherent merocyanine system of the dihydro forms results in a broad absorption band in the range of 515–530 nm in their UV/VIS spectra (Table 2 and Fig. 3). The dehydrogenated compounds 5, 5′ , and 7a – 7f exhibit their longest‐wavelength absorption maximum at ca. 380 nm (Table 2). In contrast to 5 and 5′, 7a – 7f in solution exhibit a blue‐green fluorescence with emission bands at around 460 and 480 nm (Table 4 and Fig. 5).     

Reaction of 2,3‐Dichloro‐1,4‐Naphthoquinone with 1‐Phenylbiguanide and 2‐Guanidinebenzimidazole

When 2,3‐dichloro‐1,4‐naphthoquinone (DCHNQ) ( 1 ) is allowed to react with 1‐phenylbiguanide (PBG) ( 2 ), 4‐chloro‐2,5‐dihydro‐2,5‐dioxonaphtho[1,2‐d]imidazole‐3‐carboxylic acid phenyl amide ( 4 ), 6‐chloro‐8‐phenylamino‐9H‐7,9,11‐triaza‐cyclohepta[a]naphthalene‐5,10‐dione ( 5 ) and 4‐dimethyl‐amino‐5,10‐dioxo‐2‐phenylimino‐5,10‐dihydro‐2H‐benzo[g]quinazoline‐1‐carboxylic acid amide ( 6 ) were obtained. While on reacting 1 with 2‐guanidinebenzimidazole (GBI) ( 3 ) the products are 3‐(1H‐benzoimidazol‐2‐yl)‐4‐chloro‐3H‐naphtho[1,2‐d]imidazole‐2,5‐dione ( 7 ) and 3‐[3‐(1H‐benzoimidazol‐2‐yl)‐ureido]‐1,4‐dioxo‐1,4‐dihydronaphthalene‐2‐carboxylic acid dimethylamide ( 8 ).     

Synthesis of 2‐Aryl‐2,3‐dihydro‐1,8‐naphthyridin‐4(1H)‐ones by Deprotective Cyclization of N‐{3‐[(2E)‐3‐Arylprop‐2‐enoyl]pyridin‐2‐yl}‐2,2‐dimethylpropanamides in Water

A new and convenient method for the preparation of 2‐aryl‐2,3‐dihydro‐1,8‐naphthyridin‐4(1H)‐ones 4 has been developed. Thus, N‐{3‐[(2E)‐3‐arylprop‐2‐enoyl]pyridin‐2‐yl}‐2,2‐dimethylpropanamides 3 are synthesized from commercially available pyridin‐2‐amine using an easily performed three‐step sequence and are subjected to cyclization with deprotection under acidic conditions in H₂O to give the desired products. Similarly, 2‐aryl‐2,3‐dihydro‐1,7‐naphthyridin‐4(1H)‐ones 8 and 2‐aryl‐2,3‐dihydro‐1,6‐naphthyridin‐4(1H)‐ones 12 can be prepared from pyridin‐3‐amine and pyridin‐4‐amine, respectively.     

Synthesis and Structure of O,O‐Diethyl N‐[(trans‐4‐Aryl‐5,5‐dimethyl‐2‐oxido‐2λ5‐1,3,2‐dioxaphosphorinan‐2‐yl)methyl]phosphoramidothioates

A study on the synthesis of the novel N‐(cyclic phosphonate)‐substituted phosphoramidothioates, i.e., O,O‐diethyl N‐[(trans‐4‐aryl‐5,5‐dimethyl‐2‐oxido‐2λ⁵‐1,3,2‐dioxaphosphorinan‐2‐yl)methyl]phosphoramidothioates 4a – l , from O,O‐diethyl phosphoramidothioate ( 1 ), a benzaldehyde or ketone 2 , and a 1,3,2‐dioxaphosphorinane 2‐oxide 3 was carried out (Scheme 1 and Table 1). Some of their stereoisomers were isolated, and their structure was established. The presence of acetyl chloride was essential for this reaction and accelerated the process of intramolecular dehydration of intermediate 5 forming the corresponding Schiff base 7 (Scheme 2).     

Synthesis of Bis‐Heterocyclic 1H‐Imidazole 3‐Oxides from 3‐Oxido‐1H‐imidazole‐4‐carbohydrazides

The reaction of 1H‐imidazole‐4‐carbohydrazides 1 , which are conveniently accessible by treatment of the corresponding esters with NH₂NH₂?H₂O, with isothiocyanates in refluxing EtOH led to thiosemicarbazides (=hydrazinecarbothioamides) 4 in high yields (Scheme 2). Whereas 4 in boiling aqueous NaOH yielded 2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thiones 5 , the reaction in concentrated H₂SO₄ at room temperature gave 1,3,4‐thiadiazol‐2‐amines 6 . Similarly, the reaction of 1 with butyl isocyanate led to semicarbazides 7 , which, under basic conditions, undergo cyclization to give 2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones 8 (Scheme 3). Treatment of 1 with Ac₂O yielded the diacylhydrazine derivatives 9 exclusively, and the alternative isomerization of 1 to imidazol‐2‐ones was not observed (Scheme 4). It is important to note that, in all these transformations, the imidazole N‐oxide residue is retained. Furthermore, it was shown that imidazole N‐oxides bearing a 1,2,4‐triazole‐3‐thione or 1,3,4‐thiadiazol‐2‐amine moiety undergo the S‐transfer reaction to give bis‐heterocyclic 1H‐imidazole‐2‐thiones 11 by treatment with 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione (Scheme 5).     

A two‐dimensional cadmium(II) coordination polymer constructed from 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate and 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate ligands

Crystals of poly[[aqua[μ₃‐4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylato‐κ⁵O¹O^1′:N³,O⁴:O⁵][μ₄‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylato‐κ⁷N³,O⁴:O⁴,O^4′:O¹,O^1′:O¹]cadmium(II)] monohydrate], {[Cd₂(C₁₅H₁₄N₂O₄)(C₁₆H₁₄N₂O₆)(H₂O)]·H₂O}_n or {[Cd₂(Hcpimda)(cpima)(H₂O)]·H₂O}_n, (I), were obtained from 1‐(4‐carboxybenzyl)‐2‐propyl‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃cpimda) and cadmium(II) chloride under hydrothermal conditions. The structure indicates that in‐situ decarboxylation of H₃cpimda occurred during the synthesis process. The asymmetric unit consists of two Cd²⁺ centres, one 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate (Hcpimda²⁻) anion, one 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate (cpima²⁻) anion, one coordinated water molecule and one lattice water molecule. One Cd²⁺ centre, i.e. Cd1, is hexacoordinated and displays a slightly distorted octahedral CdN₂O₄ geometry. The other Cd centre, i.e. Cd2, is coordinated by seven O atoms originating from one Hcpimda²⁻ ligand and three cpima²⁻ ligands. This Cd²⁺ centre can be described as having a distorted capped octahedral coordination geometry. Two carboxylate groups of the benzoate moieties of two cpima²⁻ ligands bridge between Cd2 centres to generate [Cd₂O₂] units, which are further linked by two cpima²⁻ ligands to produce one‐dimensional (1D) infinite chains based around large 26‐membered rings. Meanwhile, adjacent Cd1 centres are linked by Hcpimda²⁻ ligands to generate 1D zigzag chains. The two types of chains are linked through a μ₂‐η² bidentate bridging mode from an O atom of an imidazole carboxylate unit of cpima²⁻ to give a two‐dimensional (2D) coordination polymer. The simplified 2D net structure can be described as a 3,6‐coordinated net which has a (4³)₂(4⁶.6⁶.8³) topology. Furthermore, the FT–IR spectroscopic properties, photoluminescence properties, powder X‐ray diffraction (PXRD) pattern and thermogravimetric behaviour of the polymer have been investigated.     

Layer‐by‐layer Assembled Multilayers of Graphene/Mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin for Detection of Dopamine

Graphene/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin multilayer films composed of graphene sheet (GS) and mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (NH₂‐β‐CD) were fabricated easily by two steps. First, negatively charged graphene oxide (GO) and positively charged mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (NH₂‐β‐CD) were layer‐by‐layer (LBL) self‐assembled on glassy carbon electrode (GCE) modified with a layer of poly(diallyldimethylammonium chloride) (PDDA). Then graphene/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (GS/NH₂‐β‐CD) multilayer films were built up by electrochemical reduction of graphene oxide/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (GO/NH₂‐β‐CD). Combining the high surface area of GS and the active recognition sites on β‐cyclodextrin (β‐CD), the GS/NH₂‐β‐CD multilayer films show excellent electrochemical sensing performance for the detection of DA with an extraordinary broad linear range from 2.53 to 980.05 µmol·L^?1. This study offers a simple route to the controllable formation of graphene‐based electrochemical sensor for the detection of DA.     

Embryotoxicity studies of tri‐n‐butyltin(IV) complexes of 5‐[(E)‐2‐(aryl)‐1‐diazenyl]‐2‐hydroxybenzoic acid and 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl] benzoic acid on sea urchin development

The toxicity studies of free 5‐[(E)‐2‐(aryl)‐1‐diazenyl]‐2‐hydroxybenzoic acid and 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and their tri‐n‐butyltin(IV) complexes were evaluated by using sea urchin early developmental stages as recommended model organisms for toxicity tests. The novel complexes, as the parent tri‐n‐butyltin(IV) chloride (TBTCl), caused mitosis block and induced high embryonic mortality in sea urchin. Copyright © 2005 John Wiley & Sons, Ltd.     

A Simple Multistep Conversion of 1,2‐Dihydro‐1,1‐dimethoxynaphthalen‐2‐ones to (3,4‐Dihydro‐3,4‐dioxonaphthalen‐2‐yl)acetates

On irradiation (λ=350 nm) in the presence of 1,1‐dimethoxyethene, naphthalene‐1,2‐dionemonoacetals 1 regioselectively afford 1,1,4,4‐tetramethoxycyclobuta[a]naphthalen‐3‐ones 3 . Sequential deprotection of these bis‐acetals first lead to 1,1‐dimethoxycyclobuta[a]naphthalene‐3,4‐diones 4 and then to cyclobuta[a]naphthalene‐1,3,4‐triones 6 , which, in turn, are converted into (3,4‐dihydro‐3,4‐dioxonaphthalen‐2‐yl)acetates 7 by treatment with SiO₂/MeOH/air.