bluuebunny/crossref_metadata_2025 huggingface dataset:
Common and specific contributions of the intraparietal sulci to numerosity and length processing
Authors: Dormal Valérie , Pesenti Mauro
Published: March 2009

Numerical and spatial magnitude processing have long been intimately associated, leading to the suggestion that they share a common system of magnitude representation. Although separate investigations on the cerebral areas involved in numerosity and spatial estimation point toward the parietal cortex, the precise anatomical overlap, if any, has not yet been directly established. Here, functional magnetic resonance imaging was used to localize the cerebral network involved in processing both numerosity and length. Blood oxygenation level‐dependent signal changes were measured while healthy volunteers were making numerosity comparisons on linear arrays of dots, and length comparisons on discrete linear arrays of dots and continuous rectangles. The results show the bilateral involvement of parietal regions around the intraparietal sulci in explicit and implicit processing of numerosity, and a right lateralized occipitoparietal network activation in length processing; numerosity and length processing both activate the right IPS and the precentral gyrus. By excluding the mandatory intrinsic spatial processing of arrays, we demonstrate that the left IPS is involved in numerosity processing only, whereas the right IPS underlies a common processing mechanism or representation of spatial and numerical magnitude. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.
Synthesis of the new adducts of imines and enamines with PH acids and their derivatives
Authors: Prishchenko Andrey A. , Livantsov Mikhail V. , Novikova Olga P. , Livantsova Ludmila I. , Milaeva Elena R.
Published: March 2009

Nucleophilic or radical addition of esters of trivalent organophosphorus acids with PH fragments to various imines and enamines is proposed as convenient methods for the synthesis of new substituted aminomethyl organophosphorus compounds with three‐, four‐, and five‐coordinated phosphorus. Also the new functionalized derivatives of these compounds with acyl and methanesulfonyl moieties are synthesized, and some properties of the obtained compounds are presented. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:70–80, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20513
Direct conversion of secondary phosphine oxides and H‐phosphinates with [Di(acyloxy)iodo]benzenes to phosphinic and phosphonic amides
Authors: Hubacz Anna , Makowiec Slawomir
Published: March 2009

The reaction of [di(acyloxy)iodo]benzene with secondary phosphine oxides or H‐phosphinates in the presence of primary or secondary amines allows one to obtain phosphinic or phosphonic acids amides in the one‐pot process. We take advantage of the strong acylating system DAIB/R2P(O)H to phosphinylation of amines. However, the reaction mechanism is multipathway and causes yields of phosphinic or phosphonic acids amides to be moderate. When the concentration of amines is low, the intermolecular process plays a main role leading to the formation of carboxylic amides through mixed phosphoric–carboxylic anhydride, and also in the low concentration of amines, tetrahydrofuran effectively competes with the amines in the nucleophilic attack on the acylating intermediates. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:81–86, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20514
Synthesis of novel aminophosphonic acids with hydantoin structure
Authors: Todorov Petar T. , Naydenova Emilia D. , Troev Kolio D.
Published: March 2009

The novel α‐aminophosphonic acids with hydantoin structure have been synthesized reacting 5,5‐dimetylhydantoin with formaldehyde and phosphorus trichloride, or via Kabachnik–Fields reaction. Their structures were proved by means of IR, 1H, 13C{1H}, and 31P NMR spectroscopy. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:87–90, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20515
N,N‐dimethylamino‐functionalized basic ionic liquid catalyzed one‐pot multicomponent reaction for the synthesis of 4H‐benzo[b]pyran derivatives under solvent‐free condition
Authors: Chen Lu , Li Yi‐Qun , Huang Xu‐Jiang , Zheng Wen‐Jie
Published: March 2009

A simple, clean, and environmentally benign three‐component process for the synthesis of 4H‐benzo[b]pyran derivatives using basic ionic liquid N,N‐dimethylaminoethylbenzyldimethylammonium chloride ([PhCH2Me2N+CH2CH2NMe2]Cl−) as an efficient catalyst under solvent‐free condition is described. A wide range of aromatic aldehydes easily undergoes condensation with malononitrile and 5,5‐dimethylcyclohexane‐1,3‐dione (dimedone) under solvent‐free condition to afford the desired products of good purity in excellent yields. Taking into account environmental and economical considerations, the protocol presented here has the merits of environmentally benign, simple operation, convenient workup, and good yields. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:91–94, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20516
One‐pot synthesis of primary 1‐aminophosphonates: Coupling reaction of carbonyl compounds, hexamethyldisilazane, and diethyl phosphite catalyzed by Al(OTf)3
Authors: Sobhani Sara , Tashrifi Zahra
Published: March 2009

Al(OTf)3 has been utilized as a new and efficient catalyst for the selective synthesis of primary 1‐aminophosphonates by a one‐pot coupling reaction of various types of aldehydes/ketones, hexamethyldisilazane, and diethyl phosphite under solvent‐free conditions. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:109–115, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20517
Sparing the ortho‐position in nucleophilic aromatic substitution‐specific displacement of the 4‐SePh group in 2,4‐bis(phenylseleno)nitrobenzene
Authors: Stuhr‐Hansen Nicolai , Götze Thorstein Finn , Henriksen Lars , Sølling Theis Ivan , Langkilde Annette , Sørensen Henning Osholm
Published: March 2009

Upon treatment of o‐ and p‐(phenylseleno)nitrobenzenes with sodium methoxide quantitative exchange reactions took place, affording the corresponding methoxynitrobenzenes. Upon reaction between 2,4‐bis(phenylseleno)nitrobenzene 2 and sodium methoxide, an unusual regiopure formation of 4‐methoxy‐2‐(phenylseleno)nitrobenzene 3 was observed. This product remained unreactive toward an excess of sodium methoxide, thus preventing the formation of 2,4‐dimethoxynitrobenzene 6. The nature of the reactants and of the intermediate Meisenheimer complexes was examined by synthetic investigations, x‐ray crystallography, and DFT calculations. We found that the observed selectivity can be understood in terms of traditional resonance considerations. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:101–108, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20519
A facile preparation of 2‐(2‐arylethyl)‐ and 2‐(aminomethyl)indoles
Authors: Nagarathnam Dhanapalan
Published: March 2009

An important process for the acid catalyzed cleavage of the benzoyl group from 3‐benzoylindoles in high yield is identified and its application for the facile syntheses of 2‐substituted indoles is demonstrated by preparing some 2‐(2‐arylethyl)‐ and 2‐(aminomethyl)indoles from 1,3‐dibenzoyl‐2‐bromomethylindole (7).
Functionalised enaminones and their use in heterocyclic synthesis
Authors: Greenhill John V. , Chaaban Ibrahim , Steel Peter J.
Published: March 2009

A series of enaminones derived from 2,4‐dioxocyclohexane carboxylic acid esters has been prepared. The use of some of the new derivatives in the synthesis of some quinazolones and imidazoloquinazolines is illustrated.
Synthesis of substituted 14‐crown‐4 compounds
Authors: Czech Bronislaw P. , Zazulak Wolodymyr , Kumar Anand , Olsher Uriel , Feinberg Hadar , Cohen Shmuel , Shoham Gil , Dalley N. Kent , Bartsch Richard A.
Published: March 2009

Seventeen new substituted 14‐crown‐4 derivatives 3‐10, 35‐40, 42, 45 and 46 are described. A series of nine compounds 2‐10 with two, three or four substituents in the 6‐ and/or 13‐positions was synthesized in good yields from the appropriate diols and ditosylates using improved cyclization conditions. The solid state structures of 6,6,13,13‐tetra(benzyloxymethyl)‐14‐crown‐4 (8) and lithium thiocyanate complexes of trans‐ and cis‐6,13‐bis(spiro‐2,2‐dichlorocyclopropyl)‐14‐crown‐4 (45) and (46), respectively, have been determined.
Synthesis of N‐phenylpyrrole and pyrazole amidines and related diamines
Authors: Jarvest Richard L. , Marshall Joanne E.
Published: March 2009

N‐Phenylpyrrole and pyrazole nitriles 3,4,10 were prepared in one step from the corresponding aldehydes. The nitriles were converted into novel amidines 5,6,14 and related diamines 7,8,12 were also prepared from the aldehydes. The orientation of the phenyl ring to the basic function was controlled by modifying the torsional angle between the rings by methyl group substitution on the heterocycle.
A short synthesis of 5′‐O‐trityl‐protected threo‐ and erythro‐ 3′‐cyano‐3′‐deoxythymidine epimers using free‐radical chemistry
Authors: Bankston Donald D. , Almond Merrick R.
Published: March 2009

A reinvestigation of a synthetic route to 5′‐O‐trityl‐protected erythro‐CNT that incorporates a modification of the Stork radical cyclization‐cyanation reaction generates an unexpected threo‐epimer.
Synthesis of novel bicyclic pyridazine nucleosides
Authors: Lee Sang‐Gyeong , Choi Sam‐Yong , Yoon Yong‐Jin
Published: March 2009

The synthesis of some [6:6]‐ or [6:5]‐fused bicyclic pyridazin‐6‐one nucleosides, starting from 4,5‐dichloro‐3‐nitro(or amino) and 3‐hydrazinopyridazin‐6‐one nucleosides is described.
5,7,12,14‐Tetramethyldimethoxybenzo[b,i][1,4,8,11]tetraazacyclodecine, a new tumoricidal pseudo‐porphyrin
Authors: Czuchajowski Leszek , Morra Matthew , Kubaszewski Eugeniusz , Malinski Tadeusz
Published: March 2009

The title compound, a mixture of two isomers differing in the position of a methoxy substituent in one benzene ring, was obtained in a Ni‐templated synthesis directly as a water soluble dihydrochloride of the free base. The cyclic voltametry study indicated that in a neutral solution the reduction and oxidation are irreversible one electron processes, the latter leading to cation radical undergoing polymerization, a process followed by deposition of a film on the electrode. In 1,2‐dichloroethane the cation radical is oxidized to a dication, both species being much less stable than those originating from meso‐tetraphenylporphyrin. The title compoud at 2.5 × 10−5 M in Tris buffer showed a 50% inhibition of the growth of malignant melanoma cells as compared to a 44% inhibition shown by a water soluble meso‐monomethoxy‐tris(N‐methylpyridinium)porphyrin. The exposure to light for 30 minutes at 2.5 times smaller concentration increased the inhibition caused by the pseudo‐porphyrin from 9% to 49%.
On the oximation of diaryl‐β‐diketones
Authors: Bandiera T. , Grünanger P. , Albini F. Marinone
Published: March 2009

The reaction of asymmetrically substituted β‐diketones with hydroxylamine to give 3,5‐diarylisoxazoles has been re‐investigated, and has been found to occur with a low degree of site‐selectivity unless steric effects are operating. The isoxazole that has the more electron‐deficient aryl group in position 3 is formed preferentially when the reactions are run with hydroxylamine hydrochloride. When the reactions are performed in a neutral medium, a reversed site‐selectivity is observed. Steric effects have a much stronger influence on the selectivity of the reaction: when a substituent is present in the ortho position(s) of the phenyl ring, the heterocycle bearing the ortho‐substituted phenyl group in position 5 is obtained as the sole product both in acidic and in neutral medium.
A new synthetic route to polyaza‐crown macrocycles through the per(N‐formyl)polyaza‐crowns
Authors: Bradshaw Jerald S. , Krakowiak Krzysztof E. , An Haoyun , Izatt Reed M.
Published: March 2009

Seven new per(N‐formyl)polyaza‐crown macrocycles 1‐7 containing 14 to 21 ring members have been synthesized in yields of over 40% via the cyclization reaction of the appropriate per(N‐formyl)polyamine 11‐13 with the appropriate ditosylate, dibromide or diiodide. Three of the per(N‐formyl) macrocycles 5‐7 were hydrolyzed under acidic conditions to give the unsubstituted polyaza macrocycles 8‐10 in yields of over 77%.
Reactions of tetrasulfur tetranitride with bromomethyl ketones. One pot synthesis of 3,5‐diaroyl‐ and 3,5‐diacyl‐1,2,4‐thiadiazoles
Authors: Cho Jaeeock , Kim Kyongtae
Published: March 2009

Reactions of tetrasulfur tetranitride (S4N4) with aryl and alkyl bromomethyl ketones1in chlorobenzene at reflux temperature gave 3,5‐diaroyl‐ and 3,5‐diacyl‐1,2,4‐thiadiazoles2in 17‐60% yields. No 1,2,5‐thiadiazoles were detected. By heating of the two reactants at 115° without the solvent were also obtained2in 5‐13% yields. Hydrolysis of2with sodium hydroxide in a mixture of ethanol, ethyl acetate, and water (v:v, 4:2:1) at 75° to 85° afforded the heretofore inaccessible 3‐aroyl‐ and 3‐acyl‐1,2,4‐thiadiazoles3in 17‐79% yields.
New heterocyclic structures. [1,2,5]Thiadiazolo[3′,4′:4,5]pyrimido‐[2,1‐b][1,3]thiazine and thiazolo[3,2a][1,2,5]thiadiazolo[3,4‐d]pyrimidine
Authors: Pecorari Piergiorgio , Rinaldi Marcella , Costi M. Paola , Antolini Luciano
Published: March 2009

Derivatives of two new molecular structures, namely, 7,8‐dihydro‐6H,10H‐[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1‐b][1,3]thiazin‐10‐one and 6,7‐dihydro‐9H‐thiazolo[3,2‐a][1,2,5]thiadiazolo[3,4‐d][pyrimidin‐9‐one, and derivatives of N‐substituted sulfamic acid, namely, (8‐amino‐3,4‐dihydro‐2H,6H‐pyrimido[2,1‐b][1,3]thiazin‐6‐on‐7‐yl)sulfamic acid and (7‐amino‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐on‐6‐yl)sulfamic acid, were separated out as by‐products in the reduction reaction of 8‐amino‐3,4‐dihydro‐7‐nitroso‐2H,6H‐pyrimido[2,1‐ b][1,3]thiazin‐6‐one and 7‐amino‐2,3‐dihydro‐6‐nitroso‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐one derivatives, respectively, with sodium hydrosulfite.

A mechanism of reaction, which hypothesizes the action of sodium hydrosulfite in an asymmetic form, is proposed.

The results of single‐crystal X‐ray investigation on 7,8‐dihydro‐6H,10H‐[1,2,5]thiadiazolo[3′,4′:4,5]pyrimido[2,1‐b][1,3]thiazin‐10‐one (R = 0.032 for 863 reflections) and (8‐amino‐3,4‐dihydro‐2H,6H‐pyrimido[2,1‐b]‐ [1,3]thiazin‐6‐on‐7‐yl)sulfamic acid, sodium salt (R = 0.028 for 3507 reflections) are reported.
The total synthesis of β‐lapachone
Authors: Amaral Aná Claudia F. , Barnes Roderick A.
Published: March 2009

The synthesis of β‐lapachone has been accomplished in eight steps with an overall yield of twenty‐three percent starting from alpha‐naphthol. The yields from the various steps were sufficiently good to insure that the derivatives of β‐lapachone which might be effective against Chagas' disease could be obtained in reasonable amounts.
Synthesis of the four stereoisomers of several 3‐(1‐aminoethyl)pyrrolidines. Important intermediates in the preparation of quinolone antibacterials
Authors: Schroeder Mel C. , Kiely John S. , Laborde Edgardo , Johnson Don R. , Szotek Deedee L. , Domagala John M. , Stickney Thomas M. , Michel Andre , Kampf Jeffrey W.
Published: March 2009

The use of S‐α‐methylbenzyl as a chiral auxiliary at N1 allowed separation of diastereomeric 2‐pyrrolidinones substituted with an ester, ketoester, ketone and oxime at the C4 position. Reduction of each diastereomer of 4‐[1‐(hydroxyimino)ethyl]‐1‐(1‐phenylethyl)‐2‐pyrrolidinone, 10s and 10r, provided a pair of epimeric amines, [11sr and 11ss] and [11rs and 11rr], that were separated by chromatography. The four stereoisomers of 4‐(1‐aminoethyl)‐1‐(1‐phenylethyl)‐2‐pyrrolidinone, 11, were elaborated into several stereochemically pure 3‐(1‐aminoethyl)pyrrolidines, 1 and 15‐23. These compounds are useful intermediates (C7 side chains) for quinolone antibacterials.
Synthesis of derivatives of pyrazolo[1,5‐a]pyrrolo[1,2‐c][1,3,6]‐benzotriazocine, a new class of compounds with potential CNS activity
Authors: Costanzo Annarella , Bruni Fabrizio , Guerrini Gabriella , Selleri Silvia , Aiello Petra Malmberg , Lamberti Claudia
Published: March 2009

The synthesis of derivatives of pyrazolo[1,5‐a]pyrrolo[1,2‐c][1,3,6]benzotriazocine was obtained by the reaction of arylaldehydes with some 1‐(2‐aminophenyl)‐5‐(pyrrol‐1‐yl)pyrazoles, as hydrochlorides. Characterization of this new class of compounds was effected with ir, pmr and13C nmr spectral data.
Synthesis and reactivity of furo[2,3‐e]pyrrolo[1,2‐a][1,4]diazepin‐9‐one
Authors: Povazanèc Frantisek , Decroix Bernard , Morel Jean
Published: March 2009

A convenient method for the synthesis of furo[2,3‐e]pyrrolo[1,2‐a][1,4]diazepin‐9‐one is described. It has been C‐alkylated with amine (piperidine, morpholine, 4‐methylpiperazine) and N‐alkylated with alkyl halides (methyl iodide and benzyl chloride).
Syntheses of triazolo[6,7‐d]phthalide and triazolo[6,7‐d]dihydrocoumarin
Authors: Katritzky Alan R. , Ji Fu‐Bao , Fan Wei‐Qiang , Beretta Paolo , Bertoldi M.
Published: March 2009

Triazolo[6,7‐d]phthalide has been synthesized in a seven step sequence from phthalide in 24% overall yield, and triazolo[6,7‐d]dihydrocoumarin has been prepared in nine steps from dihydrocoumarin in 20% overall yield. The 1H and 13C nmr spectra and the tautomeric equilibria of the final compounds and intermediates are discussed.
Synthesis of 3‐nitro‐ and 3‐aminoquinoline‐2,4‐diones. An unexpected route to 3‐hydroxyquinoline‐2,4‐diones
Authors: Stadlbauer Wolfgang , Lutschounig Herbert , Schindler Gerda , Witoszynskyj Theo , Kappe Thomas
Published: March 2009

Nitration of 3‐substituted‐4‐hydroxy‐2(1H)‐quinolones 1 with nitric acid leads either to 3‐nitro‐ 2 or 3‐hydroxyquinolinediones 3, depending on the reaction conditions. 3‐Substituted‐3‐hydroxyquinolinediones 3 are also obtained by oxidative hydroxylation with peracetic acid. Amination of 3‐substituted‐3‐chloroquinolinediones 4 with ammonium hydroxide predominantly leads again to 3‐substituted‐3‐hydroxyquinolinediones 3, only in one case the 3‐aminoquinolinedione 5 could be isolated. With morpholine or pyridine as amines the expected 3‐aminoquinolinediones 6 and 7 were obtained.
Synthesis and stereochemistry of (3α)‐6β,7β‐dihydroxy‐ and 6β‐hydroxy‐8‐alkyl‐8‐azabicyclo[3.2.1]octane‐3‐spiro‐5′‐imidazoline‐2′,4′‐diones
Authors: Villacampa Mercedes , Martínez Manuel , González‐Trigo Gregorio , Söllhuber Mó Nica M.
Published: March 2009

The synthesis of 6β‐hydroxy‐ and 6β,7β‐dihydroxy‐8‐alkyl‐8‐azabicyclo[3.2.1]octane‐3‐spiro‐5′‐hydantoins was stereoselectively achieved by Bucherer‐Bergs reaction of the corresponding ketones. An α configuration on C3 was proposed for all hydantoins on the basis of spectral data.
Synthesis of 6‐amino‐2‐aryl‐1,2‐dihydro‐3H‐pyrido[2,3‐d]pyrimidin‐4‐one derivatives
Authors: Monge A. , Martinez‐Merino V. , Simon M. A. , Sanmartin C.
Published: March 2009

This paper reports the synthesis of new pyrido[2,3‐d]pyrimidin‐4‐one derivatives as diuretic agents. Starting with 1,2‐dihydro‐5‐nitro‐2‐oxo‐3‐pyridinecarboxylic acid 1, ethyl 2‐ethoxy‐5‐nitro‐3‐pyridincarboxylate 4 was obtained. Compound 4 reacts with ammonia, methylamine or S‐methylpseudothiourea to give the respective 2‐amino‐5‐nitro‐3‐pyridinecarboxamide derivatives 5 and 6 or 2‐methylthio‐6‐nitro‐3H‐pyrido[2,3‐d]pyrimidin‐4‐one 8. Treating carboxamide 5 with arylaldehydes and zinc dichloride, new 2‐aryl‐1,2‐dihydro‐6‐nitro‐3H‐pyrido[2,3‐d]pyrimidin‐4‐ones 9 were synthetised. These compounds reduced with iron(II) hydroxide gave 6‐amino‐2‐aryl‐1,2‐dihydro‐3H‐pyrido[2,3‐d]pyrimidin‐4‐ones 10 as expected.
1‐Chloro‐2‐azapropenylium and 1‐chloro‐2,4‐diazabutenylium salts. Intermediates for the synthesis of pyrido[1,2‐a]‐1,3,5‐triazinium salts
Authors: Okide George Bosah
Published: March 2009

1‐Chloro‐1,3‐bis(dimethylamino)‐3‐phenyl‐2‐azaprop‐2‐en‐1‐ylium perchlorate obtained from the reaction of phosphorus oxychloride‐N,N‐dimethylbenzamide complex and dimethylcyanamide reacts with 2‐amino‐4‐methylpyridine to yield 8‐methyl‐4‐dimethylamino‐2‐phenylpyrido[1,2‐a]‐1,3,5‐triazinium perchlorate (8). The structure is established by X‐ray crystallography. Various suitably substituted pyridines react similarly to afford the corresponding pyrido[1,2‐a]‐1,3,5‐triazinium salts. The intermediates obtained from several secondary amides give identical products when treated with the same pyridines. The limitations of this procedure are investigated.
Synthesis and photochemical degradation of N‐arylmethyl derivatives of the herbicide 3‐amino‐1,2,4‐triazole
Authors: Er‐Rhaimini Abderrahman , Mornet René
Published: March 2009

Reaction of an arylmethyl halide with 3‐amino‐1,2,4‐triazole (1) allows the preparation of the three N‐aryl‐methyl derivatives of 1 bearing the substituent on the heterocyclic nitrogen atoms. In basic medium (methoxide anion in DMF or methanol, or in benzene by phase transfer catalysis), the isomers 3 and 5 substituted at N‐1 and N‐2 respectively are obtained, while the isomer 4 is isolated from neutral medium (DMF). The isomers 3 and 4 may be also prepared by cyclization of appropriate formylguanidinium derivatives. 3‐Arylmethylamino‐1,2,4‐triazoles 2 may be obtained through reaction of 3‐chloro‐1,2,4‐triazole (6) with arylmethylamines. Photolysis of the N‐arylmethyl‐3‐amino‐1,2,4‐triazoles 2‐5 in methanol or water‐methanol mixture, induces homolytic and heterolytic cleavage of the arylmethyl‐C‐N bond giving rise to 3‐amino‐1,2,4‐triazole (1). Thus, compounds 2‐5 with arylmethyl groups able to absorb solar light may be considered as potential photoactivatable herbicides.
Alkylation of pyridine‐3,5‐dicarboxamide and pyridine‐3,5‐dicarbonitriles by radical substitution
Authors: Kanomata Nobuhiro , Nagahara Hisashi , Tada Masaru
Published: March 2009

Structural modification of NAD(P) model compounds, N,N,N',N'‐tetramethylpyridine‐3,5‐dicarboxamide (1), pyridine‐3,5‐dicarbonitrile (2), and 4‐methylpyridine‐3,5‐dicarbonitrile (3), have been explored by the reaction with alkyl radicals such as the 1‐adamantyl, tert‐butyl, and isopropyl radicals. The alkyl substitutions of compounds 1, 2, and 3 with the 1‐adamantyl and the tert‐butyl radical gave both 2‐mono and 2,6‐disubstitution products, whereas the reaction of compound 2 with the isopropyl radical gave 2‐mono 6c, 2,4‐di 7c, 2,6‐di 8c, and 2,4,6‐trisubstitution 9c products.
α‐Pyrones. II. Synthesis of tetrahydroquinoline derivatives of 4‐aminobutanoic and 2‐amino‐2‐pentenedioic acids
Authors: Bombarda Carlo , Erba Emanuela , Gelmi Maria Luisa , Pocar Donato
Published: March 2009

Ethyl 3‐benzoylamino‐2‐oxo‐6‐triphenylphosphoranylidenemethyl‐2H‐pyran‐5‐carboxylate (1) reacts with 2‐ nitrobenzaldehydes (2) to give 6‐(2‐nitrostyryl)‐2H‐pyran‐2‐ones (3), as the E stereoisomers, in good yields. The reduction of compounds 3, performed with hydrogen over Pd/C at room temperature and 1 atmosphere, leads to a mixture of 2‐amino‐4‐tetrahydroquinolinylidene‐2‐pentenedioic acid derivatives 5a‐d as the main products, the corresponding 3‐butenoic acid derivatives 6 and a minor amount of pyrano[2,3‐c]benzazocines 9a‐c. At 40 atmospheres and 90°, the reduction gives 4‐amino‐2‐tetrahydroquinolinylbutanoic acid derivatives 8a‐d as the main products and their precursors 7a,b,d as the minor ones. Amines 4c,d are isolated by stopping the reduction after the uptake of 3 equivalents of hydrogen.
Methyl imidazo[1,2‐b]pyridazine‐2‐carbamates and related compounds as potential antifilarial agents
Authors: Mourad Alaa E. , Wise Dean S. , Townsend Leroy B.
Published: March 2009

A series of imidazo[1,2‐b]pyridazines have been synthesized for antifilarial evaluation. The compounds prepared include methyl 6‐benzoylimidazo[1,2‐b]pyridazine‐2‐carbamate (12), 6‐benzoyl‐2‐t‐butylimidazo[1,2‐b]pyridazine (13), methyl 6‐(4‐fluorobenzoyl)imidazo[1,2‐b]pyridazine‐2‐carbamate (14), and methyl 6‐(2‐thienylcarbonylcarbonyl)imidazo[1,2‐b]pyridazine‐2‐carbamate (15) which are aza analogs of the anthelmintic agents mebendazole, flubendazole and nocadazole. In addition, the preparation of a series of 2‐t‐butylimidazo[1,2‐b]‐pyridazine‐6‐carboxylic acid derivatives is described. Electrophilic bromination and iodination substitutions of 2‐t‐butyl‐6‐methylimidazo[1,2‐b]pyridazine afforded 3‐halo derivatives. Methyl 6‐(4‐fluorobenzoyl)pyridazine‐3‐carbamate was also prepared for antifilarial evaluation. None of these compounds possessed significant antifilarial activity against Brugia pahangi or Acanthocheilonema viteae infections in jirds.
4,5‐Dihydroisoxazole and 4,5‐dihydro‐1,2,4‐oxadiazole derivatives from cycloaddition reactions of nitrile oxides to alkyl N‐(diphenylmethylene)‐α,β‐dehydroamino acids
Authors: Balsamini Cesarino , Spadoni Gilberto , Bedini Annalida , Tarzia Giorgio , Lanfranchi Maurizio , Pellinghelli Maria Angela
Published: March 2009

The alkyl N‐(diphenylmethylene)‐α,β‐dehydroamino acids 1 have been submitted to 1,3‐dipolar cycloadditions with nitrile oxides. The reactivity of these compounds depends on the type and on the stereochemistry of the β‐substituents. With the unsubstituted terms 1a,b the reaction occurs on the C,C double bond, providing a good method for the synthesis of the 4,5‐dihydroisoxazole derivatives 3a,b,c and for the gem‐functionalized 4,5‐dihydroisoxazoles amino carboxylic ester 5. The β‐substituted compounds 1c,d,e, inert to 1,1‐dimethylethylnitrile oxide, undergo the reaction to the N,C double bond, thus giving with 2a,b the 4,5‐dihydro‐1,2,4‐oxadiazole derivatives 4. All the reactions occur with high site‐ and regioselectivity.
Reactions of thioquinanthrene with sodium alkanethiolates. The smiles rearrangement of diquinolinyl sulfides
Authors: Pluta Krystian
Published: March 2009

Reactions of thioquinanthrene 1 with sodium alkanethiolates or S‐alkylisothiouronium salts (in the presence of sodium hydroxide) at 70° in DMSO or DMF yielded 4,4′‐dialkylthio‐3,3′‐diquinolinyl sulfides 3, which were results of the S‐S type of the Smiles rearrangement of primary reaction products ‐ sodium 3‐quinoline‐thiolates 6. When the reactions were carried out at 20° the products were 3′,4‐dialkylthio‐3,4′‐diquinolinyl sulfides 2.
A novel synthesis of methyl cis‐(3‐thienyl)glycidate with 2‐aminothiophenol and the synthesis of [1,5]benzothiazepine derivatives
Authors: Lancelot Jean Charles , Letois Bertrand , Rault Sylvain , Saturnino Carmela , Robba Max , De Caprariis Paolo
Published: March 2009

The synthesis of cis‐2,3‐dihydro‐3‐hydroxy‐2‐(3‐thienyl)[1,5]benzothiazepin‐4(5H)‐one derivatives is described starting from 2‐aminothiophenol and methyl cis‐(3‐thienyl)glycidate. The structures were confirmed by 1H‐nmr spectroscopy.
Electrophilic acetylation and bromination reactions of benzo[b]naphtho[2,3‐e][1,4]dioxin
Authors: Piórko Adam , Crook Michelle , Sampson Peter
Published: March 2009

The reactivity of benzo[b]naphtho[2,3‐e][1,4]dioxin in the electrophilic aromatic substitution reactions has been studied. Friedel‐Crafts acetylation resulted in the formation of three out of the possible five monoacetylated products, with the acetyl group located in positions 8 (major), 7 and 6 (minor) of the heterocycle. In the bromination reaction a higher selectivity was observed with the 6‐bromo derivative found as the only monobrominated product and the 6,11‐dibromo derivative found as the only polybrominated product. A ratio of unreacted heterocycle:6‐bromo:6,11‐dibromo derivatives in the bromination reaction has been found to depend strongly on the reaction conditions and on the heterocycle:bromine ratio.
The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 8. [1]Benzothieno[2,3‐c]naphtho[1,2‐h]quinoline and [1]benzothieno[2,3‐c]naphtho[1,2‐h][1,2,4]triazolo[4,3‐a]quinoline
Authors: Sasaki Kenji , Castle Raymond N.
Published: March 2009

The previously unknown polycyclic heterocyclic ring systems, namely, [1]benzothieno[2,3‐c]naphtho[1,2‐h]‐quinoline and [1]benzothieno[2,3‐c]naphtho[1,2‐h][1,2,4]triazolo[4,3‐a]quinoline were synthesized via photocyclization of 3‐chloro‐N‐(1′‐phenanthryl)benzo[b]thiophene‐2‐carboxamide.
Selective N‐methylation of ethyl esters of 3‐(1H‐imidazol‐4‐yl)‐2‐propenoic acid
Authors: Mawlawi H. , Monje M. C. , Lattes A. , Rivère M.
Published: March 2009

Methods of selective methylation of the nitrogen atoms of the ethyl ester of 3‐(1H‐imidazol‐4‐yl)‐2‐propenoic acid are reported. The nitrogen atom α to the ethylenic chain was methylated after protection of the β nitrogen with a phenacyl group.
Orientation effects in the nitration of the dithieno[b,d]pyridine N‐oxides. Its dependence on acidity of the reaction medium
Authors: Gronowitz Salo , Szabó Kálmán J. , Olugbade Tiwalade A.
Published: March 2009

The nitration of three dithienopyridine‐N‐oxides was investigated. The regiochemistry of the reaction was dependent on the reaction conditions used. Under strongly acidic conditions the positional preference is similar for the N‐oxides and free bases. However, under mildly acidic or neutral conditions a completely different substitution pattern was obtained. In the latter case those ring positions were substituted which are expected to be unfavored or forbidden in electrophilic substitution of the free bases. The structures of the nitro derivatives were proven by extensive use of 1H and 13C nmr spectroscopy.
Indole alkaloids from the roots of an african plant securidaca longipedunculata. I. Isolation by column chromatography and preliminary structural characterization by mass spectrometry
Authors: Costa Carlo , Bertazzo Antonella , Allegri Graziella , Curcuruto Ornella , Traldi Pietro
Published: March 2009

The extraction and the isolation of some alkaloids from the roots of an African plant (Securidaca Longipedunculata Fres) are reported. The structural characterization was performed by mass spectrometry. Alternative ionization methods (FAB and EI), collisionally‐induced decomposition experiments and accurate mass measurements revealed the presence of elymoclavine and dehydroelymoclavine and the presence of a new ergoline alkaloid.
A new type of deoxygenation of quinoxaline N‐oxides
Authors: Kurasawa Yoshihisa , Katoh Ritsuko , Kureyama Tomomi , Yoshishiba Noriko , Takada Atsushi , Kim Ho Sik , Okamoto Yoshihisa
Published: March 2009

The reaction of 6‐chloro‐2‐[2‐(p‐chlorobenzylidene)‐1‐methylhydrazino]quinoxaline 4‐oxide 3a or 2‐[2‐(p‐bromobenzylidene)‐1‐methylhydrazino]‐6‐chloroquinoxaline 4‐oxide 3b with dimethyl acetylenedicarboxylate under reflux in N,N‐dimethylformamide resulted in deoxygenation to give 6‐chloro‐2‐[2‐(p‐chlorobenzylidene)‐1‐methylhydrazino]quinoxaline 4a or 2‐[2‐(p‐bromobenzilidene)‐1‐methylhydrazino]‐6‐chloroquinoxaline 4b, respectively, while the reaction of compound 3a or 3b with dimethyl acetylenedicarboxylate under reflux in dioxane precipitated dimethyl 8‐chloro‐4‐[2‐(p‐chlorobenzyli‐dene)‐1‐methylhydrazino]‐3aH‐isoxazolo[2,3‐a]quinoxaline‐2,3‐dicarboxylate 6a or dimethyl 4‐[2‐(p‐bromobenzylidene)‐1‐methylhydrazino]‐8‐chloro‐3aH‐isoxazolo[2,3‐a]quinoxaline‐2,3‐dicarboxylate 6b, respectively. Further refluxing of compound 6a or 6b in N,N‐dimethylformamide provided compound 4a or 4b, respectively.
Studies in organic mass spectrometry. Part 15 [1]. Electron ionization mass spectra of some 5‐nitro‐3‐thiophenecarboxanilides
Authors: Ceraulo Leopoldo , De Maria Paolo , Fontana Antonella , Frascari Sara , Spinelli Domenico
Published: March 2009

The study of the electron ionization mass spectra of 5‐nitro‐3‐thiophenecarboxanilides 1‐24 has shown peculiar effects induced by the 5‐nitro group on the fragmentation of molecular ions M and the thenoyl cation a (Scheme 1). A comparison of the abundances of the important fragment ions for 5‐nitro‐3‐thiophene‐carboxanilides with those of the corresponding 3‐thiophenecarboxanilides shows that the extent of C‐N amide bond cleavage decreases in the former series as a consequence of the increased bond strength. The produced ion a does not eliminate carbon monoxide as 2‐ and 3‐thenoyl cations usually do. Again this behaviour depends on the electronic effects of the nitro group which strongly destabilizes the 5‐nitro‐3‐thienyl cation and consequently strengthens the carbon‐3 carbonyl carbon bond. Recalling the behavior of the previously studied 2‐ and 3‐thiophenecarboxanilides most of the 2′‐substituted 5‐nitro‐3‐thiophenecarboxanilides give loss of the ‘ortho’ substituent of the phenyl ring furnishing the cyclic ion g(Scheme 2). In the instance of 2′‐alkyl substituted derivatives the formation of abundant ions h' by loss of 5‐nitrothenoyl radical from M (Scheme 3) was observed, thus confirming the occurrence of a cryptic ‘ortho’ effect. The results are also discussed in relation to those obtained on some related benzoylanilides.
Synthesis of 3‐vinylpiperidine
Authors: Lowen Gregory T. , Almond Merrick R. , Rideout Janet L.
Published: March 2009

A novel synthesis of 3‐vinylpiperidine from commercially available ethyl 3‐pyridylacetate is described.
Prognostic effect of pathologic fracture in localized osteosarcoma: A cohort/case controlled study at a single institute
Authors: Kim Min S. , Lee Soo‐Yong , Lee Tae R. , Cho Wan H. , Song Won S. , Cho Sang H. , Lee Jun A. , Yoo Ji Y. , Jung Sung T. , Jeon Dae‐Geun
Published: March 2009

Background

The negative prognostic role of pathologic fracture in osteosarcoma is not determined, as previous case–control and retrospective cohort studies have produced contradictory results.

Methods

We conducted both cohort (n = 384) and case–control (n = 111) studies on 37 pathologically fractured localized osteosarcoma of extremity.

Results

In cohort study, patients with a fracture showed a tendency of poorer survival, but the difference did not reach the level of significance (5‐year metastasis‐free survival rates; 48% for cases vs. 61% for controls; P = 0.06). A case–control study on 37 fractured and 74 control recruited from 347 patients matched for tumor size and location showed no survival difference between the cases and controls (P = 0.12).

Conclusions

Reported negative prognostic effect of a pathologic fracture is likely to be due to confounding by tumor size and location. The present study suggests that the presence of a pathologic fracture has no prognostic relevance. J. Surg. Oncol. 2009;100:233–239. © 2009 Wiley‐Liss, Inc.
Performance comparison between two commercial EM softwares using higher order and piecewise RWG basis functions
Authors: Zhao X. W. , Liang C. H.
Published: March 2009

In this article, numerical result obtained using two different commercially available electromagnetic (EM) codes based on an integral equation method are presented. One of the methods solves the integral equation by the method of moments (MoM) using higher order basis functions (the commercially available parallel software named TIDES), and the other one solves the integral equation by MoM with a multilevel fast multipole algorithm (MLFMA) incorporating the RWG basis functions (the commercially available software FEKO). Numerical results indicate that the integral equation solver with higher order basis functions occupies less than 40% of the RAM and the execution time is significantly less when compared with that of using the RWG basis functions along with MLFMA. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1219–1225, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24271
High order bandpass filter using the first negative resonant mode of composite right/left‐handed transmission line
Authors: Lee Joo‐Young , Kim Dong‐Jin , Lee Jeong‐Hae
Published: March 2009

In this article, a high order composite right/left‐handed (CRLH) bandpass filter using the first negative resonant mode is presented. The proposed filter employs mushroom structure as CRLH transmission line. To design a high order CRLH filter, the design equations are derived by adopting the design equations of the conventional right‐handed (RH) bandpass filter because the resonant property of the first negative mode is similar to that of the first positive mode. The size of a CRLH filter is reduced by 41% when compared with that of conventional RH filter. The measured results are in good agreement with that of full wave simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1182–1185, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24273
Microwave directional filters using metamaterial closed‐loop resonators
Authors: Lobato‐Morales H. , Corona‐Chavez A. , Rodriguez‐Asomoza J.
Published: March 2009

The design and construction of two Metamaterial (MTM) directional filters (DF) for multiplexing applications at 900 MHz is presented. The four‐port filters are realized using composite‐right‐left‐handed (CRLH) closed‐loop resonators, which present small dimensions and suppression of harmonic resonances due to the zeroth‐order resonance produced by MTM's. The first filter uses two conventional transmission lines (TL) between resonators to generate the necessary constructive‐destructive interference for directional behavior. The second design is further miniaturized by a CRLH TL. The simulated responses are compared with measured data showing good agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1155–1156, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24275
SCM transmission in MM fiber with automatic selection of the subcarrier frequency
Authors: Kowalczyk Marcin , Siuzdak Jerzy
Published: March 2009

Demonstrated was a 10 Mbit/s binary frequency shift keying subcarrier multiplexing system operating beyond the pass‐band of 1 km MM graded index optical fiber. The system automatically adjusted the carrier frequency to the fiber frequency response. Transmission of four 10 Mbit/s channels was also shown over the same fiber. No visible channel interaction was observed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1212–1214, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24277
Small printed CPW‐fed triangular monopole antenna for ultra‐wideband applications
Authors: Choi Sung Tae , Hamaguchi Kiyoshi , Kohno Ryuji
Published: March 2009

A novel small size coplanar waveguide (CPW)‐fed monopole antenna with wide bandwidth and small group delay variation is proposed for ultra‐wideband (UWB) applications. It consists of a triangular patch with a pair of wide stubs on the lower sides thereof and linearly tapered coplanar ground planes. The measured return loss of the fabricated antenna is better than −10 dB from 2.9 to 13.2 GHz. The radiation pattern is nearly omni‐directional and the variation of the measured group delay between two proposed antennas is less than 0.94 ns over the entire UWB band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1180–1182, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24278
Slow‐wave characteristics of a 1D EBG structure for a miniaturized monopole antenna
Authors: Kim S. H. , Oh K. H. , Lim H. , Song J. I. , Jang J. H.
Published: March 2009

Transmission line and monopole antenna embedded with one‐dimensional electromagnetic bandgap (1D EBG) structure were designed, fabricated, and characterized. The slow wave characteristics of a 1D EBG cell were verified using an electro‐optic near‐field mapping system. The group velocity of the electric pulse propagating along the coplanar waveguides loaded with the 1D EBG cell was effectively slowed down compared with that of the pulse propagating along the normal coplanar waveguide without a 1D EBG cell. The slow wave characteristics were utilized to reduce the size of the monopole antenna. A compact monopole antenna could be designed by incorporating a 1D EBG cell on the radiator of the antenna. The fabricated 1D EBG monopole antenna exhibited a 58% reduction in size and performance that was comparable to a large reference monopole antenna. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1231–1235, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24284
Bandpass filter modeling employing Lorentzian distribution
Authors: Al Ahmad Mahmoud , Papaioannou George , Plana Robert , Russer Peter
Published: March 2009

This letter takes a close outlook of modeling a bandpass filter performance with the Lorentzian distribution function. Lorentzian function parameters are correlated with the filter parameters, namely, its bandwidth and center frequency. The zeros and poles of the filter are extracted from the closed form expression of the Lorentzian function, which is used to construct the rational model of the filter. This procedure is expected to optimize the overall filter performance and to construct a consistent equivalent circuit from its computed poles and zeros. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1167–1169, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24288
Improvement of compactness of low pass and band pass filter using a simple combination of cross‐defected ground structure and a discontinuous microstrip line
Authors: Boutejdar Ahmed , Omar Abbas
Published: March 2009

This article presents a method to reduce the size of LPF/BPF using defected ground structure (DGS). The DGS filter structure employs two cross‐slots etched in the ground plane. To validate the feasibility of the proposed design method, a low‐pass filter with 0.1‐dB ripple is designed, fabricated, and measured. Then a simple technique to transform the designed BPF to a LPF was presented. Additionally, a new suspended Layer's technique will be used with DGS in order to reduce more the size and to suppress the second harmonic in reject band. The second order band pass filter was designed using the proposed technique and their simulation results confirmed the validity of the technique. Simulated and measured results of the proposed filters are presented and show good agreements. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1191–1195, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24291
Compact wideband tag antenna for UHF RFID
Authors: Lim Sang Ho , Oh Young Cheol , Lim Ho , Myung Noh Hoon
Published: March 2009

A UHF radio frequency identification tag antenna using an inductively coupled feeding method and meander lines is proposed. The antenna has a compact size (diameter: 0.08λ, 26.4 mm), wide bandwidth, and simple matching technique between a tag antenna and a tag chip. To get a physical operation of the proposed antenna, a simplified structure is presented and analyzed. An equivalent circuit model with a simplified structure has good results compared with a simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1291–1294, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24295
Effect of the conductive coating thickness on performance of the microstrip reflectarray
Authors: Abbosh Amin M.
Published: March 2009

Effect of thickness of the conductive coating on performance of the microstrip reflectarray is investigated. The unit cell used in this article is in the form of a cross shaped ring. Dimensions of the utilized cell are chosen such that it resonates at the X‐band. The simulated and measured results show that increasing thickness of the conductive layer decreases the losses significantly, reduces the phase slope and shifts the resonant frequency to a higher value, while it has a negligible effect on the phase range. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1288–1290, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24296
Multi‐soliton generation using a micro ring resonator system for DWDM based soliton communication
Authors: Pornsuwancharoen N. , Dunmeekaew U. , Yupapin P. P.
Published: March 2009

We propose a new optical system that can be used to form the multi soliton pulses within the micro ring resonators. The system consists of two micro ring resonators and an add/drop multiplexer that can be integrated into a single system. The large bandwidth signal is generated by using a soliton pulse propagating in a Kerr type nonlinear medium. The tuned soliton pulses in either spatial or temporal modes are obtained by using the add/drop multiplexer. Results obtained have shown that the multi soliton pulses can be localized coherently within the micro ring waveguide. This is shown that the generation of the multi soliton pulses within the micro ring resonator is achieved, which is available for long distance communication with dense wavelength division multiplexing (DWDM). A significant increase in channel number and spacing is obtained, and the large free spectrum range (FSR) of 600 pm is achieved. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1374–1377, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24299
Compact low‐power 2.4 GHz QPSK modulator in CMOS
Authors: El‐Gabaly Ahmed M. , Saavedra Carlos E.
Published: March 2009

A compact low‐power QPSK modulator is proposed for short‐range wireless communications using a new pass‐transistor logic circuit. It is experimentally demonstrated in the unlicensed 2.4 GHz ISM frequency band using standard 0.18 μm CMOS technology, with the data rates well exceeding 100 Mbps. The core circuit occupies only 505 μm by 435 μm and consumes less than 19 mW from 1.8 V. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1344–1348, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24300
Slow wave‐modified low profile planar spiral antenna on EBG
Authors: B. A Sapna , Rao Patnam Hanumantha
Published: March 2009

A two arm Archimedean spiral antenna is modified to form various slow wave structures that have much lower operating frequency than the conventional spirals, making them compact elements for wideband array applications. Uni‐directional patterns are obtained from a slow wave modified circular star spiral with electromagnetic band gap (EBG) structure. Measured return loss of circular star spiral at 2 GHz backed by perfect electric conductor at λ/4 is −16.37 dB and this is improved to −20.25 dB when the antenna is placed over an EBG at a separation of λ/10. The radiation pattern of antenna on EBG provides a back lobe suppression of 30 dB over an isolated planar modified spiral antenna. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1270–1274, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24303
Characterization and modeling of stacked MIM on‐chip capacitors with high‐capacitance density up to 20 GHz frequency region
Authors: Moon Hyunwon , Yu Sunil , Song Seong‐Sik , Nam Ilku
Published: March 2009

In this article, double‐stacked and triple‐stacked metal‐insulator‐metal (MIM) capacitors fabricated in 0.18 μm CMOS process are reported. These provide high‐capacitance density of 2 fF/μm2 and 3.2 fF/μm2 and excellent dc and RF characteristics, respectively. The lumped circuit model of the stacked MIM capacitors is presented for high‐frequency applications up to 20 GHz. The stacked MIM capacitors offer a reduced chip area for a given capacitance value and are expected to be a viable choice for integration of RF/mixed‐mode circuits in a single chip. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1235–1238, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24305
An equilateral‐triangular microstrip antenna with polarization diversity
Authors: Sung Yongje
Published: March 2009

An equilateral‐triangular microstrip antenna with reconfigurable polarization capability is proposed. The proposed design is achieved by loading with three L‐type slits in the triangular patch and three PIN diodes are utilized to switch the slits on or off. According to the states of the diodes, the reconfigurable antenna can produce linear polarization or right hand circular polarization. An antenna prototype is implemented and measured. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1372–1374, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24306