bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational and stereoelectronic control in ring‐transformations of cis‐4,5‐dialkoxytetrahydropurine‐2,6,8‐triones
Authors: Poje Nevenka , Palković Antun , Poje Mirko 
Published: April 2009

AbstractDivergent acid‐catalysed ring‐openings of 4,5‐dimethoxytetrahydropurine‐2,6,8‐triones 2 at position 4, yielding 1‐(5‐methoxyhydantoin‐5‐carbonyl)ureas 4 (R7 = Me) or 5‐methoxy‐5‐ureido‐2,4,6‐pyrimidinetriones 5 (R7 = H), can be rationalized by assuming a preference for one of two conformational isomers of the cis‐fused system, associated with the N‐substitution effects. Intramolecular transamidation 5 → 4 presumably occurs via a bicyclic acid aminal type intermediate 3, heretofore misassigned as the reaction product. A curious base‐catalysed rearrangement was encountered with the 5 (R1 = R3 = Me, R7 = H) cases, which afforded 5‐methoxy‐1,5‐bis(methylaminocarbonyl)hydantoins 7. Remarkable stability of the conformationally rigid propellane type 4,5‐ethylenedioxytetrahydropurine‐2,6,8‐triones 9 toward acids, shows that the mode of ring‐opening at position 4 is controlled by powerful Stereoelectronic factors. However, an alternative ring‐opening at the 1,6‐bond has occurred on heating aqueous solutions of 9a (R7 = H); the ensuing decarboxylative rearrangement leads to 1,3‐dimethylallantoin (12) and its precursor, 1‐(2‐hydroxyethoxy)‐2,4‐dimethyl‐3,7‐dioxo‐2,4,6,8‐tetraazabicyclo[3.3.0]octane(11).
Synthesis of 6,7‐dihydrobenzo[4,5]cyclohept‐[1,2‐b]indol‐12(5H)‐one and related compounds
Authors: Joseph B. , Cornec O. , Mérour J.‐Y. , Solans X. , Font‐Bardia M. 
Published: April 2009

AbstractThe synthetic routes of 6,7‐dihydrobenzo[4,5]cyclohept[1,2‐b]indol‐12(5H)‐one 5 from either 1‐methyl or 1‐sulfonylindole‐2‐carboxaldehyde 1 or ethyl 1,2‐dimethylindole‐3‐carboxylate 6 are reported. The structure of the ketone 5a was confirmed by X‐ray crystallography. Several indole derivatives have been prepared with potential antitumor activity.
Ring‐transformation reactions of 5‐hydroxy‐2‐oxabicyclo[3.2.0]‐heptan‐4‐ones and 5‐hydroxy‐2‐oxabicyclo[3.2.0]hept‐6‐en‐4‐ones
Authors: Shimo Tetsuro , Minamishin Hidemi , Somekawa Kenichi 
Published: April 2009

AbstractDehydrochlorination of chlorinated 5‐hydroxy‐2‐oxabicyclo[3.2.0]heptan‐4‐ones, 3a‐c, which were obtained from the photo[2+2]cycloadditions between 4‐hydroxy‐3(2H)‐furanone 1 and chloroethylenes, with triethylamine gave 2‐ethenyl‐3(2H)‐furanones 4a,b or 2‐(2‐cyanoethyl)‐3(2H)‐furanone 4c. 2‐Oxa‐bicyclo[3.2.0]hept‐6‐en‐4‐ones 7 being [2+2]cycloadducts between 1 and acetylenes gave 2,3‐dihydro‐3‐oxooxepin derivatives 8 by electrocyclic rearrangement.
Syntheses of polysubstituted pyrroles and of 2,3‐disubstituted quinoxalines and substituted benzo[g]quinoxalines
Authors: Adembri Giorgio , Celli Angela Maria , Sega Alessandro 
Published: April 2009

AbstractTetraacetylethylene (1), and cis‐diacetylethylene (4) reacted under mild conditions with 3‐amino‐2‐butenoic acid methyl ester (6), benzene‐1,2‐diamine and naphthalene‐2,3‐diamine to give polysubstituted pyrroles, 2,3‐disubstituted quinoxalines and 2,3‐disubstituted benzo[g]quinoxalines respectively. Some aspects of the reactions mechanisms are discussed.
Syntheses of substituted pyrrolo[2,3‐d]imidazoles
Authors: Shafiee A. , Hadizadeh F. 
Published: April 2009

AbstractStarting from the readily available 5‐hydroxymethyl‐2‐mercapto‐1‐methylimidazole (1) substituted pyrrolo[2,3‐d]imidazoles were prepared.
2‐Mono‐ and 2,5‐bis[bis[(4‐dimethylamino)phenyl]hydroxymethyl]‐substituted furans, thiophenes and N‐methylpyrroles: New color‐formers for carbonless imaging
Authors: Katritzky Alan R. , Zhang Zhongxing , Lang Hengyuan , Jubran Nusrallah , Leichter Louis M. , Sweeny Norman 
Published: April 2009

Abstract2‐Mono‐ and 2,5‐bis[bis[(4‐dimethylamino)phenyl]hydroxymethyl]substituted furan, thiophene and N‐methylpyrrole were synthesized by mono‐ and dilithiation of furan, thiophene and N‐methylpyrrole, respectively, and subsequent reaction with Michler's ketone. The title compounds develop black or dark‐blue colors in acidic media.
Reactions of 1,2,4‐triazin‐5(2H)‐ones with phenols and aromatic amines
Authors: Chupakhin Oleg N. , Rusinov Vladimir L. , Beresnev Dmitri G. , Neunhoeffer H. 
Published: April 2009

Abstract1,2,4‐Triazin‐5(2H)‐ones 1 react as well with phenols, resorinol and its dimethyl ethers, as with dimethyland diethylaniline, yielding 6‐aryl‐1,6‐didydro‐1,2,4‐triazin‐5(2H)‐ones 2, 4–8, 12–15. Oxidation of the 1,6‐dihydroadducts 2a,b gives the corresponding 3‐aryl‐6‐hydroxyphenyl‐1,2,4‐triazin‐5(2H)‐ones 3a,b. Rection of 1,2,4‐triazinones 1 with 2‐naphthylamine leads to destruction of the 1,2,4‐triazine ring yielding benzo[e]indole‐2,3‐dione 19.
Synthesis of dithia‐ and tetrathiacyclophanes incorporating isoxazole units
Authors: Hatta Taizo , Kawano Muneob , Maeda Hironori , Tsuge Otohiko 
Published: April 2009

AbstractThe reaction of 5‐bromomethyl‐3‐(p‐bromomethylphenyl)isoxazole with o‐, m‐, and p‐bis(mercap‐tomethyl)benzenes gave the corresponding dithia‐ and/or tetrathiaisoxazolophanes, whose relative yields strongly depended upon the nature of the mercaptomethyl compound. The above isoxazole dibromide reacted with the bis(mercaptomethyl)isoxazole to afford a mixture of two isomeric dithiaisoxazolophanes.
Synthesis of Dialkyl 1,4‐Dihydro‐2,6‐dimethyl‐4‐(heteroaryl)‐pyridine‐3,5‐dicarboxylates as Calcium Channel Antagonists
Authors: Anana Raymond D. , Knaus Edward E. 
Published: April 2009

AbstractThe Hantzsch condensation of the heteroarylcarboxaldehydes 3a‐c with alkyl acetoacetates 4a‐c and alkyl 3‐aminocrotonates 5a‐b afforded the respective dialkyl 1,4‐dihydro‐2,6‐dimethyl‐4‐(heteroaryl)‐pyridine‐3,5‐dicarboxylates 6a‐f possessing a C‐4 4‐quinolinyl, 8‐quinolinyl or 1‐oxido‐4‐pyridinyl substituent Calcium channel antagonist structure‐activity relationships acquired indicate that i) the position of the quinolyl nitrogen atom was not a determinant of activity, ii) increasing the size of the C‐3 and C‐S alkyl ester substituents decreases potency and iii) a C‐4 1‐oxido‐4‐pyridinyl substituent abolishes activity. The most active, and equipotent C‐4 4‐quinolinyl 6a and 8‐quinolinyl 6b analogs, were approximately 8‐fold less potent calcium channel antagonists than the reference drug nifedipine.
New anti‐tumor agents. 3. Phenolic benzopyran lactone and amine derivatives
Authors: Jurd Leonard 
Published: April 2009

Abstract2‐Aminopyridine, sesamol and 4‐hydroxy‐3,5‐dimethoxybenzaldehyde condense to form a Mannicb base 3b which reacts with tetronic acid to yield lactone 4c. Cyclization of 4c yields the benzopyran lactone 1b; this inhibits growth of tumors in NCI in vitro tests. Alkaline hydrolysis of acetylated and methylated intermediate lactones, e.g. 4e, in the presence of acetone leads to the formation of novel lactones, e.g., of type 6, which incorporate the acetone nucleus. Compound 6 is of interest since it inhibits tumor growth in vitro and has been selected by NCI for ongoing in vivo testing with human cancers. Heating 3b with mixtures of propionaldehyde and secondary amines such as morpholine leads to 3‐methylbenzopyrans containing the amine nucleus, e.g. 7b. Unlike 3,4,5‐trimethoxyphenyl compounds, e.g. 7a, phenolic analogs of type 7b do not inhibit growth of tumors in vitro.
Reaction of 5‐amino‐1‐phenylpyrazole‐4‐carbonitriles with dimethyl acetylenedicarboxylate. Synthesis and structural determination of trimethyl 4,8‐dioxo‐1‐phenyl‐4,5,5a,8‐tetrahydro‐1H‐pyrazolo[3,4‐e]indolizine‐5,5a,6‐tricarboxylate derivatives
Authors: Tominaga Yoshinori , Yoshioka Noriko , Castle Raymond N. , Luo Jiann‐Kuan , Hata Tadashi 
Published: April 2009

AbstractThe reaction of 5‐amino‐1‐phenylpyrazole‐4‐carbonitriles 1a‐c with dimethyl acetylenedicarboxylate in the presence of potassium carbonate in dimethyl sulfoxide gave trimethyl 4,5,5a,8‐tetrahydro‐1‐phenyl‐4,8‐dioxo‐1H‐pyrazolo[3,4‐e]indolizine‐5,5a,6‐tricarboxylate derivatives 3a‐c from the basic solution. The products were formed by a double Michael reaction of 1 with dimethyl acetylenedicarboxylate followed by cyclization to the cyano group. The structure of product 3a was established by X‐ray crystallography.
A new efficient route to imidazo[4,5‐c]pyrazol‐5‐ones
Authors: Vicentini Chiara B. , Veronese Augusto C. , Manfrini Maurizio 
Published: April 2009

AbstractThe synthesis of imidazo[4,5‐c]pyrazol‐5‐ones (6) is reported. 5‐Amino‐4‐ethoxycarbonylaminopyra‐zoles 3a‐g when heated at 200° for 2 hours afford 6a‐g. In a similar manner imidazo[4,5‐c]pyrazol‐5‐one (6a) is readily obtained from 4‐amino‐5‐ethoxycarbonylaminopyrazole (5a).
On the relocation of the amino functionality to the ethyl side chain in aminoglutethimide: Synthesis and aromatase‐inhibitory activity of 3‐(2′‐N,N‐diethyl‐amino)ethyl‐3‐phenylpiperidine‐2,6‐dione
Authors: Moniz George A. , Hammond Gerald B. 
Published: April 2009

AbstractAminoglutethimide [3‐(4‐aminophenyl)‐3‐ethylpiperidine‐2,6‐dione] has been used clinically in the treatment of metastatic breast carcinoma. Inhibition of tumor growth is due to interference with estrogen biosynthesis. However, its action is not specific and its metabolism gives rise to toxic and non‐inhibitory metabolites. We sought to explore the impact of relocating the amino group in aminoglutethimide to the ethyl side chain. To that end, we now report the synthesis and aromatase‐inhibitory activity of 3‐(2′‐N,N‐diethylamino)ethyl‐3‐phenylpiperidine‐2,6‐dione 5. The introduction of the amino functionality on the ethyl group is accomplished via reductive animation of aldehyde 8, prepared in three steps from benzyl cyanide. The synthetic route presented can be used for the preparation of related derivatives of aminoglutethimide.
A new route to the improved synthesis of 1‐(alkoxymethyl)‐5‐alkyl‐6‐(arylselenenyl)uracils
Authors: Lee Namkyu , Kim Young‐Woo , Kim Key H. , Kim Dae‐Kee 
Published: April 2009

AbstractA new route to C‐6‐selenenyl analogs of compound 1a from 5‐alkyl‐6‐chlorouracils 6a‐b has been described. A mild and highly efficient synthesis of 1‐(alkoxymethyl)‐5‐alkyl‐6‐(arylselenenyl)uracils 8a‐e has been accomplished from 6a‐b in good yields using a two step procedure. Silylation of 5‐alkyl‐6‐chlorouracils 6a‐b using N,O‐bis(trimethylsilyl)acetamide followed by regioselective alkylation of the silylated intermediate with ethyl or benzyl chloromethyl ether in dichloromethane afforded the desired 1‐(alkoxymethyl)‐5‐alkyl‐6‐chlorouracils 7a‐d in 88–94% yields. Compounds 7a‐d readily underwent addition‐elimination reaction with an appropriate arylselenol in the presence of ethanolic sodium hyroxide to produce the corresponding 1‐(alkoxymethyl)‐5‐alkyl‐6‐(arylselenenyl)uracils 8a‐e in excellent yields (94–99%).
Synthesis of 5‐ethylpyrimidine nucleoside analogs
Authors: Takenaka Keiko , Muraoka Masako , Tsuji Tadakazu 
Published: April 2009

AbstractThis paper describes the synthesis of acyclic, cyclic, and deoxy sugar nucleosides of 5‐ethylpyrimidine, i.e., i) 1‐(2‐hydroxyethoxymethyl), 1‐(2‐methoxyethoxymethyl), and 1‐ethoxyethyl derivatives of 5‐ethyl‐uracil and 5‐ethylcytosine, ii) 5‐ethyl‐1‐(tetrahydro‐2H‐pyran‐2‐yl)‐ and ‐1‐(tetrahydrofuran‐2‐yl)uracils, and iii) 5‐ethyl‐2′‐deoxyuridine.
Nitration in the imidazo[1,2‐a]pyrazine series. Experimental and computational results
Authors: Vitse Olivier , Bonnet Pierre‐Antoine , Bompart Jacques , Viols Henri , Subra Guy , Chapat Jean‐Pierre , Grassy Gérard 
Published: April 2009

AbstractNitration was carried out on a series of imidazo[1,2‐a]pyrazine derivatives. The reactivities of diversely substituted derivatives and of all positions of substitution were analysed and experimental results compared with 13‐nmr data and semi empirical calculations (AMI). Although the unsubstituted heterocycle is highly resistant to nitration, electron‐donating groups such as alkoxy or alkylamino on position 8 enhance the reactivity of the imidazo[1,2‐a]pyrazine derivatives towards electrophilic substitution and, more specifically, nitration. The 13‐nmr experiments, electronic distributions and Molecular Electrostatic Potential isodensity surfaces calculated on the neutral forms are in good agreement with experimental results indicating position 3 is the most reactive position towards nitration.
Nucleophilic addition to substituted 1H‐4,5‐dihydroimidazolium salts
Authors: Salerno Alejandra , Ceriani Vanina , Perillo Isabel A. 
Published: April 2009

Abstract1H‐4,5‐Dihydroimidazolium salts 1 react readily with nucleophilic reagents originating cyclic products which may be stable or become transformed into acyclic compounds maintaining the structural ethylenediamine unit. With methylmagnesium iodide compound 1e affords the expected imidazolidine, but in the case of substituted 1‐aryl‐3‐methyl‐2‐phenyl salts 1b‐d the N‐aryl‐N′‐methylethylenediamines 3b‐d and acetophenone (4) were isolated, the process representing the transfer of the C‐2 unit to a nucleophilic carbon. With alkaline cyanides salts 1 react efficiently affording α,α‐diaminonitriles 5. In these compounds the cyano group may be readily substituted by nucleophiles (hydroxyl anion, species with nucleophilic carbon and reagents that act by hydride ion transfer), in a way similar to the salts but with better yields.
Syntheses of five potential heterocyclic amine food mutagens
Authors: Tanga M. J. , Bupp J. E. , Tochimoto T. K. 
Published: April 2009

AbstractThe syntheses of the potential heterocyclic amine food mutagens, 3,5,7‐trimethyl‐2‐aminoimidazo‐[4,5‐b]pyridine, 1,4,7‐trimethyl‐2‐aminoimidazo[4,5‐c]pyridine, 1,6,7‐trimethyl‐2‐aminoimidazo[4,5‐c]‐pyridine, 3,4,6‐trimethyl‐2‐aminoimidazo[4,5‐c]pyridine, and 1,4,6‐trimethyl‐7‐aminoimidazo[4,5‐c]‐pyridine are described.
Substituted ethyl 2‐acyl‐3‐amino‐6‐methylthieno[2,3‐b]pyridine‐4‐carboxylates as synthons for novel heterocycles
Authors: Coppo Frank T. , Fawzi Maged M. 
Published: April 2009

AbstractThe triethylamine‐catalyzed reaction of 4‐substituted ethyl 2‐acyl‐3‐amino‐6‐methylthieno[2,3‐b]pyridine‐4‐carboxylates IIIa‐h with 2,2,6‐trimethyl‐4H‐1,3‐dioxin‐4‐one IV gave 4‐substituted ethyl 3‐acetyl‐2‐hydroxy‐7‐methylthieno[2,3‐b:4,5‐b′]dipyridine‐9‐carboxylates Va‐h. Some of the thienodipyridines (V) reacted with excess IV to give 5‐substituted ethyl 3‐acetyl‐4,8‐dimethyl‐2‐oxo‐2H‐pyrano[2,3‐b]‐pyrido[3′,2′:4,5]thieno[2,3‐e]pyridine‐10‐carboxylates VI.
Synthesis, structure and reactivity of imidazo[1,2‐a][1,8]naphthyridines
Authors: Gueiffier Alain , Viols Henri , Blache Yves , Chapat Jean Pierre , Chavignon Olivier , Teulade Jean Claude , Fauvelle Florence , Grassy Gérard , Dauphin Gérard 
Published: April 2009

AbstractThe synthesis and reactivity of imidazo[1,2‐a][1,8]naphthyridines are reported. Electrophilic substitution reactions were studied and the site of the reaction was established with the aid of high‐field 1H and 13C nmr spectra. The experimental C‐1 position reaction was correlated with a CNDO/2 calculations.
Heterocycles structurally influenced by a side chain. X. Effect of temperature and side chain on the imine‐enamine tautomerism in the quinoxalinone and pyridopyrazinone systems
Authors: Seki Taketsugu , Iwanami Yasuo , Kuwatani Yoshiyuki , Iyoda Masahiko 
Published: April 2009

Abstract3‐(1‐Benzoyl)ethyl‐1H‐pyrido[2,3‐b]pyrazin‐2‐one (7), 3‐(1‐ethoxycarbonyl)ethyl‐1H‐pyrido[2,3‐b]‐pyrazin‐2‐one (8), and 3‐(1‐benzoyl)ethyl‐1H‐quinoxalin‐2‐one (9) exist only in the imine form due to the steric effect of the methyl substituent. As regards the imine‐enamine tautomerism, 3‐(β‐carbonylmethylene) derivatives of 1,2‐dihydro‐4H‐pyrido[2,3‐b]pyrazin‐3‐one such as 12 and 15–18 gradually change from the enamine form to the imine form with elevated temperatures; however, 3‐(carbonylmethylene) derivatives of 3,4‐dihydro‐1H‐pyrido[2,3‐b]pyrazin‐2‐one such as 10, 19 and 20 show little temperature effect. 2‐Phenacylidene‐1,2‐dihydro‐4H‐pyrido[3,4‐b]pyrazin‐3‐one (21) and 3‐phenacylidene‐3,4‐dihydro‐1H‐pyrido[3,4‐b]pyrazin‐2‐one (22), which exist in the enamine form, show no temperature effect.
Benzimidazo[1,2‐c]quinazoline dimers as potential antitumor agents
Authors: Braña Miguel F. , de Vega María Jesús Pérez , Perron Denise , Conlon Donna , Bousquet Peter F. , Robinson Simon P. 
Published: April 2009

AbstractThe 6‐substituted benzimidazo[1,2‐c]quinazoline 1 is a lead structure from our DNA intercalator program and is cytotoxic to the human colon cancer tumor line HT‐29 with an inhibitory concentration 50, IC50 of 4.00 μM. In order to try and improve the limited cytotoxicity of this class of compound we prepared a series consisting of two benzimidazo[1,2‐c]quinazoline moieties linked by a polyalkylamino bridge, of different length and substitution. The compound with the ‐NH‐(CH2)3‐N(CH3)‐(CH2)3‐NH‐bridge had an inhibitory concentration 50, IC50 of 0.5 μM. When tested in vivo, however, no clear anti‐tumor activity was produced in the human breast cancer tumor line MX‐1 or the human melanoma tumor line LOX, human tumor xenografts models.
Studies on the chemistry of O,N‐ and S,N‐containing heterocycles. 16. Investigations on the synthesis of new tricyclic β‐lactams via [2+2]cycloaddition reaction
Authors: Pippich Susanne , Bartsch Herbert , Erker Thomas 
Published: April 2009

AbstractStarting from methylthioimidates 1–8 a series of corresponding tricyclic β‐lactams was synthesized via [2+2]cycloaddition with ketenes generated in situ from substituted acetyl chlorides. Dependent on the bicyclic starting material and on the substituent of the corresponding acetyl chloride N‐acetyl derivatives were obtained as by‐ or sole products.
The synthesis of azahomotryptophane derivatives. The transformation of N‐trifluoroacetyl‐5‐bromo‐4‐oxonorvaline methyl ester into 4‐(imidazo[1,2‐a]azinyl‐3)‐4‐oxohomoalanine derivatives
Authors: Škof Marko , Svete Jurij , Stanovnik Branko 
Published: April 2009

AbstractAzatryptophane homologues, 4‐(imidazo[1,2‐a]pyridinyl‐3)‐ 9a‐9f and 4‐(imidazo[1,2‐a]pyrimidinyl‐3)‐4‐oxohomoalanine derivatives 9g‐91, were prepared from N,N‐dimethyl‐N′‐(pyridinyl‐2)‐ 6a‐6f and N,N‐dimethyl‐N‐(pyriniidinyl‐2)formamidines 6g‐6i, and (S)‐N‐trifluoroacetyl‐5‐bromo‐4‐oxonorvaline methyl ester (2) and its (R,S)‐isomer.
Synthesis of novel heterocycles from 2‐amino‐3‐cyanomethyl‐sulfonyl‐4,5‐dimethylfuran
Authors: Stephens Chad E. , Sowell J. Walter 
Published: April 2009

AbstractThe synthesis and selected reactions of the versatile heterocycle 2‐amino‐3‐cyanomethylsulfonyl‐4,5‐dimethylfuran is reported. In particular, cyclization reaction of the aminofuran yielded a number of novel furo[3,2‐b]thiazine 1,1‐dioxides. Additionally, a novel tetracyclic system, namely a pyrrolo[2′,3′:5,6]‐[1,4]thiazino[3,2‐b]quinoline 4,4‐dioxide, is prepared via an intramolecular triple‐cyclization in which the furan ring is opened and reclosed as a pyrrole.
Synthesis of nitrogen‐containing heterocycles. 8. Preparation and ring‐opening of spiro[cycloalkane‐[1′,2′,4′]triazolo[1′,5′‐c]pyrimidine] derivatives
Authors: Miyamoto Yoshiko , Yamazaki Chiji 
Published: April 2009

AbstractDiaminomethylene‐ and aminomethylthiomethylenehydrazones [2] of cyclic ketones 1–8 readily reacted with ethoxymethylenemalononitrile to give spiro[cycloalkane‐1,2′‐[1,2′,4′]triazolo[1,5′‐c]pyrimidine‐8′‐carbonitrile] derivatives 12–19 through the electrocyclic reaction of the initially formed condensation products 26 in moderate to high yields. The spiro[cyclopentanetriazolopyrimidine] derivatives underwent ring‐opening at the cycloalkane moiety upon heating in solution to give 2‐alkyl‐5‐substituted‐[1,2,4]triazolo[1,5‐c]pyrimidine‐8′‐carbonitriles 20–23. When an alkyl substituent was introduced into the cyclopentane ring, cleavage of the spiro compounds occurred preferentially at the cyclopentane moiety between the spiro carbon and the more branched one. In contrast, the cyclohexane ring, especially of spiro‐5‐amino‐triazolopyrimidines 17 and 18 strongly resisted to ring‐opening under similar conditions, but those of 5‐methylthiotriazolopyrimidines 14 gave up to 17 percent of cleavage after prolonged heating in hot ethanol. 2‐t‐Butyl‐5‐methylthio‐2,3‐dihydro[1,2,4]triazolo[1,5‐c]pyrimidine‐8‐carbonitrile 25 [R3 = C(CH3)3] was highly susceptible to the cleavage even at room temperature and produced the corresponding 2‐unsubstituted triazolopyrimidine 24 with loss of the t‐butyl group.
On the synthesis and isolation of chlorocarbazoles obtained by chlorination of carbazoles
Authors: Bonesi Sergio M. , Erra‐Balsells Rosa 
Published: April 2009

AbstractCarbazole (1) undergoes electrophilic aromatic substitution with various chlorinating reagents. Although 3‐chlorocarbazole (1b), 3,6‐dichlorocarbazole (1d) and 1,3,6,8‐tetrachlorocarbazole (1f) obtained by chlorination of carbazole were isolated and characterized sometime ago, 1‐chlorocarbazole (1a), 1,6‐dichlorocarbazole (1c) and 1,3,6‐trichlorocarbazole (1e) had never been isolated from the reaction mixtures. The preparation and subsequent isolation and characterization of 1a, 1b, 1c, 1d, 1e and 1f are reported (mp, tR, Rf, 1H‐ and 13C‐nmr, ms). Physical and spectroscopic properties of 1c are compared with those of 1b and 1d in order to show that the former is the major product obtained in several chlorinating processes. As chlorinating reagents, chlorine in glacial acetic acid, sulfuryl chloride, N‐chlorosuccinimide, N‐chlorosuccinimide‐silica gel, N‐chlorobenzotriazole, and N‐chlorobenzotriazole‐silica gel in dichloromethane and in chloroform have been used and their uses have been compared. The chlorination reaction of different carbazole derivatives such as 2‐hydroxycarbazole (2), 2‐acetoxycarbazole (3), 3‐bromocarbazole (4) and 3‐nitrocarbazole (5) was also studied and the corresponding chloro derivatives 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 3e, 3f, 4a, 4b, 4c, 4d, 5a and 5b are described for the first time. Semiempirical PM3 calculations have been performed in order to predict reactivity of carbazole (1), substituted carbazoles 2–5 and chlorocarbazoles (Scheme 1). Theoretical and experimental results are discussed briefly.
Furopyridines. XXIII. Synthesis and reactions of chloropyridine derivatives of furo[2,3‐b]‐, ‐[2,3‐c]‐ and ‐[3,2‐c]pyridine
Authors: Shiotani Shunsaku , Taniguchi Katsunori 
Published: April 2009

AbstractChlorination of the N‐oxides of furo[2,3‐b]‐ 1a, ‐[2,3‐c]‐ 1b and ‐[3,2‐c]pyridine 1c with phosphorus oxychloride afforded compounds substituted normally at the α‐ or λ‐position to the ring nitrogen, 2a, 2′a, 2b, 2c, 2′c and 2′c, and in addition, in the case of 1b, compounds substituted on the furan ring, 2′b and 2″b. The structures of these compounds were confirmed from their ir, nmr and mass spectra. The major chlorinated products 2a, 2b and 2c were converted to methoxy‐ 5a, 5b and 5c, N‐pyrrolidyl‐ 7a, 7b and 7c, and phenylthiofuropyridines 8a, 8b, and 8c.
Synthesis and structural characterization of substituted thieno[2,3‐b]pyridines from o‐chloroformyl‐1,4‐dihydropyridines
Authors: Suárez Margarita , Ochoa Estael , Pita Beatriz , Espinosa Remberto , González Leandro , Martín Nazario , Quinteiro Margarita , Seoane Carlos , Soto Jose L. 
Published: April 2009

AbstractNovel 4,7‐dihydrothieno[2,3‐b]pyridines 10a‐d have been prepared in a one step procedure from the readily available o‐chloroformyl substituted 1,4‐dihydropyridines 9a‐d and ethyl mercaptoacetate in good yields. Semiempirical calculations reveal a favoured geometry with a boat conformation in the dihydropyridine system and a planar thieno ring. The calculated charge density values for the olefmic carbons (C5 and C6) are in agreement with the experimental push‐pull effect observed in the 13C nmr.
Synthesis and spectral properties of 2,3‐dihydro‐4‐(paramethylphenyl)‐7‐[(o, m‐, and p‐substituted)phenoxy]‐1H‐1,5‐benzodiazepine‐2‐thiones
Authors: Cortés Eduardo Corés , Torres Mario Martínez 
Published: April 2009

AbstractA series of twelve new 2,3‐dihydro‐4‐(para‐methylphenyl)‐7‐[(o‐, m‐, and p‐substituted)phenoxy]‐1H‐1,5‐benzodiazepine‐2‐thiones. which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3‐dimercapto‐1‐(p‐methylphenyl)‐2‐propen‐1‐one with 3,4‐diaminophenyl‐R‐phenyl ethers. The structure of all products was corroborated by ir; 1H‐nmr; 13C‐nmr and ms.