bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 10. Synthesis and structure determination of naphtho[1′,2′:4,5]thieno[3,2‐a]‐4,7‐phenanthroline
Authors: Musmar M. J. , Zektzer Andrew S. , Castle Raymond N. , Kent Dalley N. 
Published: March 2009

AbstractNaphtho[1′,2′:4,5]thieno[3,2‐a]‐4,7‐phenanthroline, a novel hexacyclic ring system has been synthesized in four steps. The 1H and 13C nmr assignments have been made using two‐dimensional nmr techniques. The tertiary helical structure was determined by X‐ray crystallographic analysis.
An evaluation of hofmann and cope elimination routes to (±)‐2‐n‐propylthietane
Authors: Woolhouse A. D. , Gainsford G. J. , Crump D. R. 
Published: March 2009

AbstractA synthetic route to (±)‐2‐n‐propylthietane 1 that utilises a silver oxide‐induced Hofmann elimination is described together with an evaluation of the potential of a Cope elimination as an alternative and more cost‐effective route to 1. Some chemistry of the isomeric intermediate thiete sulfones 5 and 12 from each of these respective eliminations is presented.
Synthesis of thieno[2,3‐d]pyrimidines from 4,6‐dichloropyrimidine‐5‐carbaldehydes
Authors: Clark J. , Shahhet M. S. , Korakas D. , Varvounis G. 
Published: March 2009

AbstractSeveral thieno[2,3‐d]pyrimidines have been prepared by intramolecular cyclisation of 6‐(substituted methylthio)‐5‐pyrimidinecarbaldehyde and carbonitrile intermediates derived from 6‐chloropyrimidine‐5‐carbaldehydes and 5‐carbonitriles and methyl thioglycolate or 5‐formylpyrimidine‐4‐(3H)‐thiones and appropriate α‐halogeno compounds. Thienopyrimidines 18 and 5c were nitrated to the corresponding nitro compounds 23 and 24. Hydrolysis at position 4 of compound 18 also occurred during nitration. The ester 5g was hydrolysed in base to the acid 25.
Synthesis of 8‐dipropylamino‐7,8,9,10‐tetrahydrophenanthridines as potential serotoninergic agonists
Authors: Castan Florence , Bigg Dennis C. H. 
Published: March 2009

AbstractA number of 8‐dipropylamino‐7,8,9,10‐tetrahydrophenanthridines have been prepared as analogs of the known serotoninergic agonist 8‐hydroxy‐2‐(dipropylamino)tetralin (8‐OH‐DPAT) and their affinity for the 5‐HT1Areceptor subtype evaluated by radioligand binding assay.
Synthesis of some benzo[h]quinoline derivatives
Authors: Janin Yves L. , Bisagni Emile , Carrez Danièle 
Published: March 2009

AbstractReaction between 6‐methoxy‐1‐tetralone, methyl propiolate and an ammonia‐saturated methanolic solution led to 5,6‐dihydro‐8‐methoxybenzo[h]quinolin‐2(1H)‐one in good yields. Subsequent aromatization, chlorination, substitution and demethylation enabled us to prepare 2‐amino‐substituted benzo[h]quinoline derivatives. These compounds, which are structurally related to the antitumor benzo[c]phenanthridine alkaloids by deletion of a ring, were tested on cultured murine lymphoblastic leukaemia cells (L1210). Results showed that they are devoid of cytotoxicity.
Synthesis, structural, conformational and pharmacological study of new fentanyl derivatives of the camphidine system
Authors: Rico B. , Gálvez E. , Izquierdo M. L. , Arias M. S. , Orjales A. , Berisa A. , Labeaga L. 
Published: March 2009

AbstractA series ofN‐phenethyl‐8‐β‐amidocamphidines4a‐f(3‐phenethyl‐8‐β‐(N‐arylamido)‐3‐azabicyclo‐[3.2.1]octane) has been designed, synthesized and stereochemically characterized as semirigid analogous of the 4‐anilidopiperidine analgesics in an attempt to study the influence of certain stereochemical factors on analgesia in this class of compounds. In deuteriochloroform and deuteriobenzene solution, compounds4a‐fdisplay the same preferred conformation. The cyclopentane and piperidine rings adopt an envelope and distorted chair conformation respectively flattened at N‐3, with the N and C‐8 substituents in equatorial and axial positions with respect to the piperidine ring.In vivopharmacological testing demonstrated that compounds4a‐fwere inactive in the analgesic test, with the exception of compound4fwhich showed an ED50of 250 mg/kg p.o.
New method of synthesis of 1,5‐benzodiazepin‐2‐ones from 4‐hydroxycoumarin
Authors: Hamdi Maǎmar , Grech Odile , Sakellariou Reine , Spézale Vincent 
Published: March 2009

AbstractA new method of synthesis of 1,5‐benzodiazepine‐2‐ones, from 4‐hydroxycoumarin and substituted 1,2‐phenylenediamines by heating in xylene or acetic acid‐ethanol, is reported.
A convenient method for regioselective C‐5 halogenation of 4(3H)‐oxo‐7H‐pyrrolo[2,3‐d]pyrimidines
Authors: Barnett Charles J. , Kobierski Michael E. 
Published: March 2009

AbstractN‐7, O‐Disilylation of 4(3H)‐oxo‐7H‐pyrrolo[2,3‐d]pyrimidines provides a convenient method for activation of these compounds toward regiospecific halogenation at C‐5. The sequence is conveniently carried out without isolation of the silylated derivatives and desilylation is spontaneous upon addition of water to the reaction mixture.
Studies on pyrazines. Part 28. Deoxydative acetoxylation of pyrazine N‐oxides
Authors: Sato Nobuhiro , Miwa Naoko , Suzuki Hiroko , Sakakibara Tohru 
Published: March 2009

AbstractDeoxydative acetoxylation of 3‐methoxy‐, 3‐phenyl‐, 3‐methyl‐, 3‐chloro‐, and 3‐methoxycar‐bonylpyrazine 1‐oxides furnished predominantly 2‐acetoxy‐6‐substituted pyrazines, some of which were more selectively prepared by addition of zinc bromide and triethylamine to the reaction. Regioselectivity of the acetoxylation is discussed based upon heat of formation by AMI and AMI‐COSMO for all possible isomers of each set.
The synthesis of azatryptophane derivatives
Authors: Svete Jurij , Stanovnik Branko , Tiŝler Miha 
Published: March 2009

AbstractOptically active and racemic isomers of aspartic acid (1) were transformed into the corresponding N‐trifluoroacetyl‐5‐bromo‐4‐oxonorvaline methyl esters (6, R = Me) and N‐trifluoroacetyl‐3‐formylalanine methyl esters 13, which were used as starting compounds in the synthesis of β‐heteroaryl substituted‐α‐amino acids.
A new procedure for the synthesis of 4H‐pyrazolo[1,5‐c][1,3,5]thiadiazine‐4‐thiones
Authors: Vicentini C. B. , Veronese A. C. , Guarneri M. , Manfrini M. , Giori P. , Guccione S. 
Published: March 2009

AbstractThiation of N‐(1‐tert‐butyl‐3‐methylpyrazol‐5‐yl)carboxamides 2 with the Lawesson reagent afforded the corresponding thiocarboxamides 3. Heating of 3 in formic acid gave the N‐dealkylated thiocarboxamides 4 which were cyclized into 4H‐pyrazolo[1,5‐c][1,3,5]thiadiazine‐4‐thiones 5 by treatment with thiophosgene.
Diazine‐substituted tert‐butylureas and tert‐butylthioureas and a convenient access to the related carbodiimides
Authors: Heinisch Gottfried , Matuszczak Barbara , Pürstinger Gerhard , Rakowitz Dietmar 
Published: March 2009

AbstractAn efficient procedure for the preparation of diazine‐substituted urea and thiourea derivatives 3a‐c, 5a‐c is proposed. On attempts to prepare the related S‐methylisothioureas 6a‐c under phase‐transfer conditions smooth conversion into carbodiimides 7a‐c was found to occur.
The methylation, oxidation and crystallographic characterization of imidazole derivatives
Authors: Vampa Gabriella , Benvenuti Stefania , Severi Fabio , Malmusi Luca , Antolini Luciano 
Published: March 2009

AbstractCompounds 2, 3 and 4 were synthesized and the crystal and molecular structures of 1 and 4 were determined. An hptlc technique for studying the methylation rate of 1 and the oxidation rate of 2 was applied.
Synthesis and antifolate activity of 2,4‐diamino‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidine analogues of trimetrexate and piritrexim
Authors: Rosowsky Andre , Mota Clara E. , Queener Sherry F. 
Published: March 2009

Abstract2,4‐Diamino‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidines with di‐ and trimethoxyaralkyl substitution at the 6‐position were synthesized from theN6‐unsubstituted compound and appropriate aralkyl bromides inN,N‐dimethylformamide solution containing a catalytic amount of sodium iodide. An improved method of preparation of 2,4‐diamino‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidine from 2‐amino‐6‐benzyl‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidin‐4(3H)‐one was also developed, in whichN2was protected by reaction with pivalic anhydride and the resulting product was subjected consecutively to reaction with 4‐chlorophenylphosphorodichloridate and 1,2,4‐triazole, ammonolysis to replace the 4‐imidazolido group and remove theN2‐pivaloyl group, and catalytic hydrogenolysis to remove the 6‐benzyl group. In assays of the ability of the products to inhibit dihydrofolate reductase fromPneumocystis carinii, andToxoplasma gondii, and rat liver the most active of the compounds tested was 2,4‐diamino‐6‐(2′‐bromo‐3′,4′,5′‐trimethoxybenzyl)‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidine. The concentration of this compound needed to inhibit enzyme activity by 50% was 0.51 μMagainst theP. cariniienzyme, 0.09 μMagainst theT. gondii enzyme, and 0.35 μMagainst the rat enzyme. Thus, there was selectivity of binding toT. gondiienzyme, but notP. cariniienzyme, relative to rat enzyme. 2′,5′‐Dimethoxybenzyl analogues were less active than the corresponding 3′,4′,5′‐trimethoxybenzyl analogues, and compounds with a CH2CH2or CH2CH2CH2bridge were less active than those with a CH2bridge. 2,4‐Diamino‐6‐(2′‐bromo‐3′,4′,5′‐trimethoxybenzyl)‐5,6,7,8‐tetrahydropyrido[4,3‐d]pyrimidine showed greater selectivity than trimetrexate or piritrexim for theP. cariniiandT. gondiienzyme, but was less selective than trimethoprim or pyrimethamine. However its molar potency against both enzymes was greater than that of trimethoprim, the antifolate most commonly used, in combination with sulfamethoxazole, for initial treatment of opportunisticP. cariniiandT. gondiiinfections in patients with AIDS and other disorders of the immune system.
A novel synthesis of 3′‐deoxy‐3′‐nitrothymidine via nucleophilic substitution with nitrite anion
Authors: Huang Jim J. , Ragouzeos Aris , Rideout Janet L. 
Published: March 2009

AbstractNucleophilic substitution at C3′ of 1‐(2‐deoxy‐5‐O‐trityl‐β‐D‐erythr‐pentofuranosyl)‐2‐methoxy‐5‐methyl‐4(1H)‐pyrimidinone (5) with methyl iodide/triphenylphosphine/diethyl azodicarboxylate gave the expected inverted iodide 6 and minor epimer 7. Treatment of 6 with lithium nitrite/phloroglucinol yielded the desired nitro derivative 8 and subsequent acidic deprotection afforded the title compound 1. This represents a novel method for the introduction of a nitro group into the furanosyl moiety of a nucleoside. The nmr spectroscopic techniques (COSY, NOESY, nOe, HMQC and HMBC) were used to determine the stereochemistry at C3′ of the nucleosides. Spectral analysis of H‐D exchange at the 3′‐position of 1 did not indicate the formation of its epimer 10.
Palladium(0)‐catalyzed allylation of 4(5)‐substituted imidazoles, 5(6)‐substituted benzimidazoles, benzotriazole and 5(6)‐methylbenzotriazole
Authors: Arnau N. , Arredondo Y. , Moreno‐Mañas M. , Pleixats R. , Villarroya M. 
Published: March 2009

AbstractPd(0)‐Catalyzed allylations of 4(5)‐nitroimidazole, 1, 2‐methyl‐4(5)‐nitroimidazole, 2, 4(5)‐bromo‐imidazole, 7, 4(5)‐methoxyimidazole, 10, 5(6)‐nitrobenzimidazole, 16a, 5(6)‐methylbenzimidazole, 16b, benzotriazole, 19, and 5(6)‐methylbenzotriazole, 22, were studied under several reaction conditions. Nitroimidazoles 1 and 2 were regioselectively allylated under thermodynamic control, leading to 1‐allyl‐4‐nitro derivatives.
Long‐range 1H‐15N correlation at natural abundance using gradient‐enhanced inverse‐detection
Authors: Crouch Ronald C. , Martin Gary E. 
Published: March 2009

AbstractInverse‐detected heteronuclear shift correlation efficiency has been significantly augmented by the incorporation of pulsed field gradients (PFG). Phase‐cycling requirements for t1‐noise suppression in gradient‐enhanced experiments are, for the most part, obviated, making it feasible to acquire data in one or a few transients/t1 increment. The benefits which acerue for 1H‐13C correlation (using GHMQC, GHMBC, and variants of GHMQC‐TOCSY) are well documented. Less obvious is the increased facility with which long‐range 1H‐15N correlation spectra can be acquired. An IDR‐(Inverted Direct Response)‐GHMQC‐TOCSY was used to establish unequivocal proton resonance assignments for the alkaloid ajmaline. Long‐range 1H‐15N heteronuclear couplings to the two nitrogen atoms of ajmaline were then probed using a gradient‐enhanced 1H‐15N heteronuclear shift correlation experiment derived from HMQC. Long‐range 1H‐15N couplings in ajmaline are assigned for the first time.
Synthesis of 4‐hydroxy‐6,9‐difluorobenz[g]isoquinoline‐5,10‐diones and conversions to 4‐hydroxy‐6,9‐bis[(aminoalkyl)amino]‐benz[g]isoquinoline‐5,10‐diones
Authors: Krapcho A. Paul , Maresch Martin J. , Gallagher Cynthia E. , Hacker Miles P. , Menta Ernesto , Oliva Ambrogio , Di Domenico Roberto , Da Re Giovanni , Spinelli Silvano 
Published: March 2009

AbstractSynthetic procedures have been developed which lead to 4‐hydroxy‐6,9‐difluorobenz[g]isoquinoline‐5,10‐dione (4a) and its 3‐methyl analogue 4b. Attempts to displace the fluorides from 4a with N,N‐dimethylethylenediamine were unsuccessful. Analogue 4a on treatment with N‐(t‐butoxycarbonyl)ethylene diamine led to 15, formed from addition of the nucleophilic amine to C‐3. On the other hand, analogue 4b, on treatment with N,N‐dimethylethylenediamine led to the anticipated difluoride displacement product 3c. The protection of the hydroxy group of 4a by benzylation with phenyldiazomethane led to 4c which on treatment with N‐(t‐butoxycarbonyl)ethylene diamine or N,N‐dimethylethylenediamine led to the corresponding 6,9‐bis‐substituted analogues 18a and 18b, respectively. Reductive debenzylations of 18a and 18b by hydrogenation over Pearlman's catalyst also effected partial reductions of the quinone. However, air oxidation of the over reduced products led to 3a and 3b, respectively. Treatment of 3a with hydrogen chloride gas led to the hydrochloride salt of 3d. Addition of O‐p‐Methoxybenzyl‐N,N'‐diisopropylurea to 4a led to the p‐methoxybenzyl analogue 4d. Treatment of 4d with N,N‐dimethylethylene diamine or N‐(t‐butoxycarbonyl)ethylene diamine led to displacements of the fluorides to yield 18c and 18d, respectively. Deprotection of 18c to 3b was accomplished using methanesulfonic acid. Treatment of 18d with trifluoroacetic acid followed by addition of maleic acid led to dimaleate salt of 3d.
Ring transformations of heterocyclic compounds. XIII. Bis(2,4,6‐triarylphenyl) substituted bispyridinium salts from methyl derivatives by double pyrylium and thiopyrylium ring transformations
Authors: Zimmermann Thomas , Schmidt Klaus 
Published: March 2009

AbstractThe synthesis of hitherto unknown 4,4′‐bis(2,4,6‐triarylphenyl) substituted bispyridinium diperchlorates 3, in which the N‐atoms are linked by a carbon chain, a heteroatom containing a carbon chain or a bis(methylene) substituted aromatic/heteroaromatic ring, from 4,4′‐dimethylbispyridinium derivatives 2 by a double 2,6‐[C5+C] ring transformation of 2,4,6‐triarylpyrylium and 2,4,6‐triarylthiopyrylium salts 1/4 is reported. Spectroscopic data of the bispyridinium diperchlorates 3 and their mode of formation are discussed.
Tetrazole compounds. 11. electron impact mass spectrometry of 1‐aryl‐5‐(l‐acyl‐2‐dialkylaminovinyl)‐1H‐tetrazoles
Authors: Fischer Gerhard W. , Herrmann Michael , Möder Monika 
Published: March 2009

AbstractThe mass spectrometric behaviour of 1‐aryl‐5‐(1‐acyl‐2‐dialkylaminovinyl)‐1H‐tetrazoles was studied, especially using 1‐phenyl‐5‐(1‐benzoyl‐2‐dimethylaminovinyl)‐1H‐tetrazole 1 and its D‐and 15N‐labeled derivatives. All tetrazoles investigated showed a clearly observable molecular ion and underwent as the main fragmentation the elimination of nitrogen followed by a number of various subsequent processes. Besides, primary fragments such as [M − N3•]+ and [M — ArN3]+• were also observed.
Synthesis and alkylation of 3,4‐dihydro‐1H‐1,3‐4‐benzotriazepine‐2,5‐diones and related systems
Authors: Karp Gary M. 
Published: March 2009

AbstractA synthesis of the 1,3,4‐benzotriazepine‐2,5‐dione 2a and its 2‐thio analog 11 is described. The key step was the mild and efficient cyclization of the o‐(aminobenzoyl)hydrazine 10, obtained from the reaction of a protected hydrazine derivative with the o‐nitrobenzoyl chloride 3. Alkylation of 2a takes place exclusively at N‐3 while alkylation of 11 takes place on sulfur. Cyclization of the o‐(aminobenzoyl)hydrazine 14 gave the 2,4(1H,3H)‐quinazolinedione 15 as the sole product.
Inhibition of folylpolyglutamate synthetase by substrate analogues with an ornithine side chain
Authors: Rosowsky Andre , Forsch Ronald A. , Moran Richard G. 
Published: March 2009

AbstractNα‐[4‐[[(4‐Aminopteridin‐6‐yl)methyl]amino]benzoyl]‐L‐ornithine (dAPA‐Orn) was synthesized, and its ability to inhibit folylpolyglutamate synthetase from mouse liver was compared with that of the corresponding 2,4‐diamino analogue APA‐Orn. Also compared were the inhibitory activities of the deaza analogues 5‐deazaAPA‐Orn, 8‐deazaAPA‐Orn, and 5,8‐dideazaAPA‐Orn, as well as those ofNα‐pteroyl‐L‐ornithine (PteOrn) and its deaza analogues 5‐deazaPteOrn and 5,8‐dideazaPteOrn. The inhibition constant Kiof dAPA‐Orn was 7‐fold greater than that of APA‐Orn, indicating that the 2‐amino group plays a role in binding to the active site. The binding affinity of the 2,4‐diamino compounds increased in the order 5‐deazaAPA < APA‐Orn <5,8‐dideazaAPA‐Orn < 8‐deazaAPA‐Orn, and that of the 2‐amino‐4(3H)‐oxo compounds increased in the order 5‐deazaPteOrn < PteOrn < 5,8‐dideazaPteOrn. The most potent inhibitor of both groups was 8‐deazaAPA‐Orn, with a Kiof 0.018 μM, coresponding to an 8‐fold and 15‐fold increase in affinity relative to APA‐Orn and 5‐deazaAPA‐Orn, respectively. The results suggest (a) that the binding of Orn‐containing folylpolyglutamate synthetase inhibitors is affected to a greater degree by replacement of N8by a carbon atom than it is by the corresponding change at N5, (b) that the effect of carbon for nitrogen replacement is greater in the 2,4‐diamino derivatives than in the 2‐amino‐4(3H)‐oxo compounds, and (c) that the 2,4‐diamines are the better inhibitors. Comparison of the Kivalues of the Orn‐containing inhibitors with the Kmvalues of the corresponding glutamate‐containing substrates revealed that Km/Kiratio can vary as much as 100‐fold depending on the nature of the heterocyclic moiety, suggesting that caution should be exercised in using Kmvalues of known substrates to predict Kivalues of putative inhibitors.
Synthesis of a series of diaminobenzo[f]‐ and diaminobenzo[h]pyrimido[4,5‐b]quinolines as 5‐deaza tetracyclic nonclassical antifolates
Authors: Donkor Isaac O. , Devraj Rajesh , Queener Sherry F. , Barrows Louis R. , Gangjee Aleem 
Published: March 2009

AbstractA series of diaminobenzo[f]‐ and diaminobenzo[h]pyrimido[4,5‐b]quinolines 1–11 were designed as 5‐deaza tetracyclic nonclassical, lipophilic antifolates. The compounds were designed as conformationally semi‐rigid and rigid analogs of 2,4‐diamino‐6‐phenyl‐12 and 2,4‐diamino‐7‐phenylpyrido[2,3‐d]pyrimidines 13 and 14. The target compounds were synthesized by cyclocondensation of chlorovinyl aldehydes obtained from appropriately substituted 1‐ or 2‐tetralone, with 2,4,6‐friaminopyrimidine. Compounds 1–11 were evaluated as inhibitors of P. carinii and T. gondii dihydrofolate reductases. These pathogens cause fatal opportunistic infections in AIDS patients. In addition, the selectivity of these agents was evaluated using rat liver dihydrofolate reductase as the mammalian source. In general the benzo[f]pyrimido[4,5‐b]quinolines 1–5 were more potent than the corresponding benzo[h]pyrimido[4,5‐b]quinoline analogues 6–11 against P. carinii and rat liver dihydrofolate reductase and were equipotent against T. gondii dihydrofolate reductase. Compounds 6–11 were moderately selective towards T. gondii dihydrofolate reductase with IC50S in the 10−7 M range. In contrast analogues 1–5 lacked selectivity against P. carinii or T. gondii dihydrofolate reductase and were, in general, potent inhibitors of rat liver dihydrofolate reductase with IC50S in the 10−8 M range. Analogues 1 and 4 were evaluated against a series of tumor cell lines in vitro and were found to have moderate antitumor activity (IC50 10−6 M). The structure activity/selectivity relationships suggest that benzo[f]pyrimido analogues 1–5 with the phenyl ring substitution in the “upper” portion of the tetracyclic ring are better accommodated within the rat liver (mammalian) dihydrofolate reductase and P. carinii dihydrofolate reductase active sites compared to the benzo[h]pyrimido analogues 6–11 which have the phenyl ring substitution in the “lower” portion of the tetracyclic ring. In contrast T. gondii dihydrofolate reductase does not discriminate between the isomers and binds to both series of compounds with similar affinities.
Synthesis of novel near‐infrared cyanine dyes for metal ion determination
Authors: Górecki Tadeusz , Patonay Gabor , Strekowski Lucjan , Chin Robert , Salazar Noe 
Published: March 2009

AbstractFour heptamethine cyanine dyes10, 19–21containing anortho‐hydroxy‐carboxy functionality for metal ion complexation and absorbing at λ max (methanol) 761±1 nm have been synthesized.
Preparation of tetrazoles from organic nitriles and sodium azide in micellar media
Authors: Jursic Branko S. , Leblanc Blaise W. 
Published: March 2009

AbstractAn effective method for the preparation of 5‐substituted tetrazoles from the corresponding nitriles in micellar media is described. It was demonstrated that almost quantitative yields of tetrazoles can be obtained if the amount of water‐surfactant is optimized. The advantages of the methods presented over many others currently used are the simplicity, facility of isolation of tetrazole products and elimination of using relatively expensive solvents and reagents.
Applications of benzotriazole methodology in heterocycle ring synthesis and substituent introduction and modification
Authors: Katritzky Alan R. , Henderson Scott A. , Yang Baozhen 
Published: March 2009

AbstractApplications of benzotriazole methodology for the preparation of heterocyclic compounds are reviewed. The characteristic advantages of benzotriazole as a synthetic auxiliary are first briefly considered. This is followed by a summary of its use in ring synthesis in which the construction of small; five‐membered; six‐membered; and larger heterocyclic rings using benzotriazole methodology are each examined separately. Finally, consideration of the use of benzotriazole in the ring annulation ‐ particularly benzannulation ‐ of heterocycles. Subsequent sections deal with the introduction of substituents into aromatic heterocycles; the ring substitution of saturated heterocycles; and benzotriazole assisted modification of heterocyclic substituents.The present review supplements a recent comprehensive review of benzotriazole chemistry [1] which covers the literature through 1996.
Synthesis of certain 5‐substituted thieno[2,3‐b]thiophene‐2‐sulfonamides and thieno[2,3‐b]thiophene‐2‐sulfonamide 6,6‐dioxides
Authors: Chen Hwang‐Hsing , May Jesse A. , Lynch Vincent M. 
Published: March 2009

AbstractA series of the title compounds were prepared for evaluation as inhibitors of carbonic anhydrase II. Oxidation of 5‐substituted thieno[2,3‐b]thiophene‐2‐sulfonamides provided the first examples of thiophene[2,3‐b]thiophene‐2‐sulfonarnide 6,6‐dioxides. These cyclic vinyl sulfones readily underwent addi tion to give predominately that 4,5‐cisaddition product.