Synthesis and reactivity of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione

An efficient synthesis of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one by bromination of dehydroacetic acid in glacial acetic acid is described. Novel 4‐hydroxy‐6‐methyl‐3‐(2‐substituted‐thiazol‐4‐yl)‐2H‐pyran‐2‐ones have been prepared from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with thioamides, thiourea, and diphenylthiocarbazone. The condensation reaction of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione, obtained from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with aliphatic amines, with benzaldehydes and acetophenones led to novel 2‐arylidene‐6‐methyl‐2H‐furo[3,2‐c]pyran‐3,4‐diones and 6‐(2‐arylprop‐1‐enyl)‐2H‐furo[3,2‐c]pyran‐3,4‐diones. The structure of all compounds was established by elemental analysis, IR, NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one: Synthesis and reactivity with amines

The synthesis and reactivity studies of 4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one 2 with nucleophiles are reported. Reactions of 2 with hydrazine derivatives gave new pyrazole‐type com pounds while the reaction with ortho‐phenylenediamines yielded 1,5‐benzodiazepines. The reaction of 2 with ethylamine implies the 2H‐pyran‐2‐one ring opening and the formation of a strong conjugated compound 3.     

Ring Enlargement and Sulfur‐Transfer Processes in SiO2‐Catalyzed Reactions of Thiocarbonyl Compounds with Optically Active Oxiranes

The reactions of 1,3‐dioxolane‐2‐thione ( 3 ) with (S)‐2‐methyloxirane ((S)‐ 1 ) and with (R)‐2‐phenyloxirane ((R)‐ 2 ) in the presence of SiO₂ in anhydrous dichloroalkanes led to the optically active spirocyclic 1,3‐oxathiolanes 8 with Me at C(7) and 9 with Ph at C(8), respectively (Schemes 2 and 3). The analogous reaction of 1,3‐dimethylimidazolidine‐2‐thione ( 4a ) with (R)‐ 2 yielded stereoselectively (S)‐2‐phenylthiirane ((S)‐ 10 ) in 83% yield and 97% ee together with 1,3‐dimethylimidazolidin‐2‐one ( 11a ). In the cases of 3‐phenyloxazolidine‐2‐thione ( 4b ) and 3‐phenylthiazolidine‐2‐thione ( 4c ), the reaction with (RS)‐ 2 yielded the racemic thiirane (RS)‐ 10 , and the corresponding carbonyl compounds 11b and 11c (Scheme 4 and Table 1). The analogous reaction of 4a with 1,2‐epoxycyclohexane (= 7‐oxabicyclo[4.1.0]heptane; 7 ) afforded thiirane 12 and the corresponding carbonyl compound 11a (Scheme 5). On the other hand, the BF₃‐catalyzed reaction of imidazolidine‐2‐thione ( 5 ) with (RS)‐ 2 yielded the imidazolidine‐2‐thione derivative 13 almost quantitatively (Scheme 6). In a refluxing xylene solution, 1,3‐diacetylimidazolidine‐2‐thione ( 6 ) and (RS)‐ 2 reacted to give two imidazolidine‐2‐thione derivatives, 13 and 14 (Scheme 7). The structures of 13 and 14 were established by X‐ray crystallography (Fig.).     

Synthesiss of novel 3‐(2‐thienyl)‐1,2‐diazepino[3,4‐b]quinoxalines with algicidal activity

The reaction of the quinoxaline N‐oxide 1 with thiophene‐2‐carbaldehyde gave 6‐chloro‐2‐[1‐methyl‐2‐(2‐thienylmethylene)hydrazino]quinoxaline 4‐oxide 5 , whose reaction with 2‐chloroacrylonitrile afforded 8‐chloro‐2,3‐dihydro‐4‐hydroxy‐1‐methyl‐3‐(2‐thienyl)‐1H‐1,2‐diazepino[3,4‐b]quinoxaline‐5‐carbonitrile 6 . The reaction of compound 6 with various alcohols in the presence of a base effected alcoholysis to provide the 5‐alkoxy‐8‐chloro‐2,3,4,6‐tetrahydro‐1‐methyl‐4‐oxo‐3‐(2‐thienyl)‐1H‐1,2‐diazepino[3,4‐b]‐quinoxalines 7a‐d . The reaction of compounds 7a and 7b with diethyl azodicarboxylate effected dehydrogenation to give the 5‐alkoxy‐8‐chloro‐4,6‐dihydro‐1‐methyl‐4‐oxo‐3‐(2‐thienyl)‐1H‐1,2‐diazepino[3,4‐b]‐quinoxalines 8a and 8b , respectively. Compounds 8a and 8b were found to show good algicidal activities against Selenastrum capricornutum and Nitzchia closterium.     

Oxidative Conversion of 3‐Alkoxyfurans to 2‐Hydroxy‐3(2H)‐furanones and 2‐Hydroxy‐2‐butene‐1,4‐diones with 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) or Phenyltrimethylammonium Tribromide (PTAB) in t‐BuOH

2‐Alkoxy‐1,3,4‐triphenylfurans were oxidized to 3‐alkoxy‐2,4,5‐triphenyl‐ 2‐butene‐1,4‐diones with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) in t‐BuOH. In contrast, various 3‐alkoxy‐2,4,5‐triphenylfurans were directly converted to 2‐hydroxy‐3(2H)‐furanone with phenyltrimethylammonium tribromide (PTAB) in t‐BuOH. The oxidative ring opening of 3‐alkoxy‐2,5‐diphenylfurans to cis‐2‐hydroxy‐2‐butene‐1,4‐dione was also accomplished with PTAB in t‐BuOH under the same reaction conditions.     

Unexpected Course of the Reaction of 2‐Unsubstituted 1H‐Imidazole 3‐Oxides with Ethyl Acrylate

The attempted ethenylation at C(2) of 2‐unsubstituted 1H‐imidazole N‐oxides with ethyl acrylate (=prop‐2‐enoate) in the presence of Pd(OAc)₂ does not occur. In contrast to the other aromatic N‐oxides, the [2+3] cycloaddition of imidazole N‐oxides predominates, and 3‐hydroxyacrylates, isomeric with the cycloadducts, are key products for the subsequent reaction. The final products were identified as dehydrated 2+1 adducts of 1H‐imidazole N‐oxide and ethyl acrylate. The role of the catalyst is limited to the dehydration of the intermediate 3‐hydroxypropanoates to give 1H‐imidazol‐2‐yl‐substituted acrylates.     

Three Questionable Cases in the Chemistry of Quinoxalines and Benzodiazepines in the Way of the Syntheses of Benzimidazoles

The reaction of 3‐ethoxycarbonylmethylene‐3,4‐dihydroquinoxalin‐2(1H)‐one 5 with the Vilsmeier reagent, the treatment of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one hydrochloride 7 with 10% sodium hydroxide and 3‐benzimidazoylquinoxaline‐2(1H)‐one 3 with both 1,2‐phenylenediamine dihydrochloride, and the reactions of 1,2‐phenylenediamine have been reinvestigated, and the structures of these reaction products have been revised. The aforementioned reactions have been shown to proceed with the formation of 1‐N,N‐dimethylaminomethylene‐2‐oxo‐1,2‐dihydrofuro[2,3‐b]quinoxaline 10 in the first case, the formation of 3‐[2‐(benzimidazol‐2‐on‐1‐yl)vinyl]‐1H‐quinoxalin‐2‐one 12 in the second case, and the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 in the third case and not the formation of 3‐(N,N‐dimethylaminocarbonyl)furo[2,3‐b]quinoxaline hydrochloride 6 , the free base of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one 7 , that is, compound 11 and benzodiazepine derivative 4 , as has been described earlier. In the third case, the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 occurs according to the novel quinoxalin‐2(1H)‐one benzimidazole rearrangement discovered by us. The potential mechanisms for the investigated reactions are discussed.     

Semisynthesis of 3′(2′)‐O‐(Aminoacyl)‐tRNA Derivatives as Ribosomal Substrate

An efficient synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated pCpA derivatives is described, which could lead to the production of (aminoacyl)‐tRNAs following T4 RNA ligase mediated ligation. The tetrahydrofuranyl (thf) group was used as a permanent protective group for the 2′‐OH of the cytidine moiety which can be removed during the purification of the 3′(2′)‐O‐aminoacylated‐pCpA. This approach allowed for a general synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated oligonucleotides. The fully protected pCpA 14 was synthesized by phosphoramidite chemistry and treated with NH₃ solution to remove the 2‐cyanoethyl and benzoyl groups (→ 15 ; Schemes 1 and 2). The 2′‐O‐thf‐protected‐pCpA 15 was coupled with α‐amino acid cyanomethyl esters, and the products 20a – c were deprotected and purified with AcOH buffer to afford 3′(2′)‐O‐aminoacylated pCpA 21a – c in high yields. The 3′(2′)‐O‐aminoacylated pCpA were efficiently ligated with tRNA(? CA) to yield (aminoacyl)‐tRNA which was an active substrate for the ribosome.     

Synthesis of Novel Disubstituted Pyrazolo[1,5‐a]pyrimidines,Imidazo[1,2‐a]pyrimidines,and Pyrimido[1,2‐a]benzimidazoles Containing Thioether and Aryl Moieties

A series of novel 6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐7‐phenylpyrazolo[1,5‐a]pyrimidines, 5‐phenyl‐6‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]imidazo[1,2‐a]pyrimidines, and 2‐phenyl‐3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]pyrimido[1,2‐a]benzimidazoles have been synthesized in four steps starting with 2‐hydroxyacetophenone. The intermediate 3‐[(1,3,4‐thiadiazol‐2‐yl)sulfanyl]‐4H‐1‐benzopyran‐4‐ones reacted with pyrazol‐3‐amines, 5‐methylpyrazol‐3‐amine, and 1H‐imidazol‐2‐amine, 1H‐benzimidazol‐2‐amine via a cyclocondensation to give the title compounds in the presence of MeONa as base, respectively. The approach affords the target compounds in acceptable‐to‐good yields. The new compounds were characterized by their IR, NMR, and HR mass spectra.     

1,3‐Dipolar Cycloaddition Reactions of Organic Azides with Morpholinobuta‐1,3‐dienes and with an α‐Ethynyl‐enamine

The cycloaddition of organic azides with some conjugated enamines of the 2‐amino‐1,3‐diene, 1‐amino‐1,3‐diene, and 2‐aminobut‐1‐en‐3‐yne type is investigated. The 2‐morpholinobuta‐1,3‐diene 1 undergoes regioselective [3+2] cycloaddition with several electrophilic azides RN₃ 2 ( a , R=4‐nitrophenyl; b , R=ethoxycarbonyl; c , R=tosyl; d , R=phenyl) to form 5‐alkenyl‐4,5‐dihydro‐5‐morpholino‐1H‐1,2,3‐triazoles 3 which are transformed into 1,5‐disubstituted 1H‐triazoles 4a , d or α,β‐unsaturated carboximidamide 5 (Scheme 1). The cycloaddition reaction of 4‐[(1E,3Z)‐3‐morpholino‐4‐phenylbuta‐1,3‐dienyl]morpholine ( 7 ) with azide 2a occurs at the less‐substituted enamine function and yields the 4‐(1‐morpholino‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 8 (Scheme 2). The 1,3‐dipolar cycloaddition reaction of azides 2a – d with 4‐(1‐methylene‐3‐phenylprop‐2‐ynyl)morpholine ( 9 ) is accelerated at high pressure (ca. 7–10 kbar) and gives 1,5‐disubstituted dihydro‐1H‐triazoles 10a , b and 1‐phenyl‐5‐(phenylethynyl)‐1H‐1,2,3‐triazole ( 11d ) in significantly improved yields (Schemes 3 and 4). The formation of 11d is also facilitated in the presence of an equimolar quantity of tBuOH. The three‐component reaction between enamine 9 , phenyl azide, and phenol affords the 5‐(2‐phenoxy‐2‐phenylethenyl)‐1H‐1,2,3‐triazole 14d .     

Synthesis of New Bis‐imidazole Derivatives

The reaction of aldimines with α‐(hydroxyimino) ketones of type 10 (1,2‐diketone monooximes) was used to prepare 2‐unsubstituted imidazole 3‐oxides 11 bearing an alkanol chain at N(1) (Scheme 2, Table 1). These products were transformed into the corresponding 2H‐imidazol‐2‐ones 13 and 2H‐imidazole‐2‐thiones 14 by treatment with Ac₂O and 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione, respectively (Scheme 3). The three‐component reaction of 10 , formaldehyde, and an alkane‐1,ω‐diamine 15 gave the bis[1H‐imidazole 3‐oxides] 16 (Scheme 4, Table 2). With Ac₂O, 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione or Raney‐Ni, the latter reacted to give the corresponding bis[2H‐imidazol‐2‐ones] 19 and 20 , bis[2H‐imidazol‐2‐thione] 21 , and bis[imidazole] 22 , respectively (Schemes 5 and 6). The structures of 11a and 16b were established by X‐ray crystallography.     

Synthesis and reactions of 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]‐quinazolin‐9‐one and 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one

The reaction of 3‐N‐(2‐mercapto‐4‐oxo‐4H‐quinazolin‐3‐yl)acetamide ( 1 ) with hydrazine hydrate yielded 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one ( 2 ). The reaction of 2 with o‐chlorobenzaldehyde and 2‐hydroxy‐naphthaldehyde gave the corresponding 3‐arylidene amino derivatives 3 and 4 , respectively. Condensation of 2 with 1‐nitroso‐2‐naphthol afforded the corresponding 3‐(2‐hydroxy‐naphthalen‐1‐yl‐diazenyl)‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one ( 5 ), which on subsequent reduction by SnCl₂ and HCl gave the hydrazino derivative 6. Reaction of 2 with phenyl isothiocyanate in refluxing ethanol yielded thiourea derivative 7. Ring closure of 7 subsequently cyclized on refluxing with phencyl bromide, oxalyl dichloride and chloroacetic acid afforded the corresponding thiazolidine derivatives 8, 9 and 10 , respectively. Reaction of 2‐mercapto‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 11 ) with hydrazine hydrate afforded 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 12 ). The reactivity 12 towards carbon disulphide, acetyl acetone and ethyl acetoacetate gave 13, 14 and 15 , respectively. Condensation of 12 with isatin afforded 2‐[N‐(2‐oxo‐1,2‐dihydroindol‐3‐ylidene)hydrazino]‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 16 ). 2‐(4‐Oxo‐3‐phenylamino‐3,4‐dihydroquinazolin‐2‐ylamino)isoindole‐1,3‐dione ( 17 ) was synthesized by the reaction of 12 with phthalic anhydride. All isolated products were confirmed by their ir, ¹H nmr, ¹³C nmr and mass spectra.     

A Convenient Synthesis of 2H‐Pyran‐2‐ones,Fused Pyran‐2‐ones,and Pyridones Bearing a Thiazole Moiety

The versatile enaminonitrile, 2‐cyano‐3‐(dimethylamino)‐N‐(4‐phenylthiazol‐2‐yl)‐acrylamide ( 2 ), reacts with some C,O‐binucleophiles (acetylacetone and dimedone) in refluxing acetic acid to afford the pyranone 4 , the chromene 6 derivatives, and with C,N‐binucleophiles (2‐(benzothiazol‐2‐yl)acetonitrile and 2‐(1H‐benzimidazol‐2‐yl)acetonitrile) to afford the respective 1H‐pyrido[2,1‐b]benzothiazole 8 and pyrido[1,2‐a]benzimidazole 10 derivatives. Similar treatment of 2 with phenol, resorcinol, α‐naphthol and β‐naphthol in boiling acetic acid gave the coumarin derivatives 12 , 14 , 16 , and 18 , respectively. The utility of enaminonitrile 2 for the synthesis of 6H‐pyrano[3,2‐d]isoxazole 20 , pyrano[2,3‐c]pyrazole 22 , and pyrano[2,3‐d]pyrimidine 24 derivatives was also explored via its reaction with 3‐phenylisoxazol‐5(4H)‐one, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one, and barbituric acid, respectively. The mechanistic aspects for the formation of the new compounds were also discussed.     

Synthesis of heterocycle‐substituted pyropheophorbide derivatives

Methyl pyropheophorbide‐a (MPPa) ( 1 ) was converted to two aldehydes, methyl 2‐formylmethyl‐2‐devinylpyropheophorbide‐a ( 2 ) and methyl 2‐formyl‐2‐devinylpyropheophorbide‐a ( 3 ). The former 2 reacted with active methylene compounds having a cyano function in the presence of sulfur to afford thiophene‐substituted chlorins 5a‐c and reacted with arylhydrazines to yield indole‐substituted chlorins 6a‐d . From the latter 3 , a α‐diketo chlorin 7 was obtained via Wittig reaction and oxidation. Compound 7 reacted with o‐phenylenediamine to afford 2‐quinoxalyl‐substituted pyropheophorbide‐a 8. The reaction of MPPa ( 1 ) with anthranilamide to give a spiro‐substituted compound 9 .     

Regio‐ and Stereoselective 1,3‐Oxathiolane Formation in the Reaction of Thiolactones with Optically Active Oxiranes

The reactions of 3H‐isobenzofuran‐1‐thione ( 1 ) with (S)‐2‐methyloxirane ( 2 ) and (R)‐2‐phenyloxirane ( 6 ) in the presence of SiO₂ in anhydrous CH₂Cl₂ led to two pairs of diastereoisomeric spirocyclic 1,3‐oxathiolanes, i.e., 3 and 4 with a Me group at C(5′), and 7 and 8 with a Ph group at C(4′), respectively (Schemes 2 and 3). In both cases, 3H‐isobenzofuran‐1‐one ( 5 ) was formed as a main product. The analogous reactions of 3,4‐dihydro‐2H‐[1]benzopyran‐2‐thione ( 9 ) and 3,4,5,6‐tetrahydro‐2H‐pyran‐2‐thione ( 14 ) with 2 and 6 yielded four pairs of the corresponding diastereoisomeric spirocyclic compounds 10 and 11, 12 and 13, 15 and 16 , and 18 and 19 , respectively (Schemes 4–7). In the reaction of 14 with 6 , the 1,3‐oxathiolane 20 with a Ph group at C(2) was also formed. The structures of 3, 7, 8, 10, 19 , and 20 were established by X‐ray crystallography (Figs. 1–4). In contrast to the thiolactones 1, 9 , and 14 , the thioesters 21a – 21d did not react with (R)‐2‐phenyloxirane ( 6 ) either in the presence of SiO₂ or under more‐drastic conditions with BF₃?Et₂O or SnCl₄ (Scheme 8). The results show that spirocyclic 1,3‐oxathiolanes can be prepared from thiolactones with oxiranes. The nucleophilic attack of the thiocarbonyl S‐atom at the SiO₂‐activated oxirane ring proceeds with high regio‐ and stereoselectivity via an S_N2‐type mechanism.     

A Novel 2H‐Azirin‐3‐amine as a Dipeptide (Aib‐Hyp) Synthon

The synthesis of methyl (2S,4R)‐4‐(benzyloxy)‐N‐(2,2‐dimethyl‐2H‐azirin‐3‐yl)prolinate ( 10 ), a novel 2H‐azirin‐3‐amine (`3‐amino‐2H‐azirine'), is described (Scheme 1). The reaction of methyl (2S,4R)‐N‐(2‐methylpropanoyl)‐4‐(benzyloxy)prolinate ( 7 ) with Lawesson reagent gave methyl (2S,4R)‐4‐(benzyloxy)‐N‐[2‐(methylthio)propanoyl]prolinate ( 8 ) and consecutive treatment with COCl₂, 1,4‐diazabicyclo[2.2.2]octane (DABCO), and NaN₃ led to 10 . The use of 10 as a building block of the dipeptide Aib‐Hyp (Aib=2‐aminoisobutyric acid, Hyp=(2S,4R)‐4‐hydroxyproline) is demonstrated by the syntheses of several model peptides (Scheme 2 and Table). The benzyl protecting group of the 4‐OH function in Hyp in the model peptides has been removed in good yields.     

Cyclocopolymerization of allyl‐acrylate quaternary ammonium salts with diallyldimethylammonium chloride

A series of copolymers of N,N‐dialkyl‐N‐2‐(methoxycarbonyl)allyl allyl ammonium chloride, N,N‐dialkyl‐N‐2‐(ethoxycarbonyl)allyl allyl ammonium chloride, and N,N‐dialkyl‐N‐2‐(t‐butoxycarbonyl)allyl allyl ammonium bromide with diallyldimethylammonium chloride (DADMAC) were prepared in water at 60 °C with 2,2′‐azo‐bis(2‐amidinopropane)dihydrochloride. A strong effect of ester substituents on cyclopolymerization was observed. The methyl and ethyl ester monomers showed high cyclization efficiencies during homopolymerizations and copolymerizations. Unexpectedly, the t‐butyl ester derivatives showed high crosslinking tendencies. Water‐soluble copolymers were obtained only with a decrease in the molar fraction of t‐butyl ester monomer below 30%. Relative reactivities of the allyl‐acrylate monomers in photopolymerizations were compared with the relative reactivity of DADMAC. Allyl‐acrylate monomers were much more reactive than DADMAC; the photopolymerization rate decreased in the following order: N,N‐morpholine‐N‐2‐(t‐butoxycarbonyl)allyl allyl ammonium bromide > N,N‐piperidyl‐N‐2‐(t‐butoxycarbonyl)allyl allyl ammonium bromide > N,N‐dibutyl‐N‐2‐(ethoxycarbonyl)allyl allyl ammonium chloride > N,N‐piperidyl‐N‐2‐(ethoxycarbonyl)allyl allyl ammonium chloride ∼ N,N‐morpholine‐N‐2‐(ethoxycarbonyl)allyl allyl ammonium chloride ∼ N,N‐piperidyl‐N‐2‐(methoxycarbonyl)allyl allyl ammonium chloride > N‐methyl‐N‐butyl‐N‐2‐(ethoxycarbonyl)allyl allyl ammonium chloride. Intrinsic viscosities of the polymers measured in 0.09 M NaCl ranged from 1.06 to 3.20 dL/g. The highest viscosities were obtained for copolymers of the t‐butyl ester monomers with piperidine and morpholine substituents. The copolymer of the t‐butyl ester with piperidine substituent and DADMAC was hydrolyzed in acid to give a polymer with zwitterionic character. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 640–649, 2001     

Pyridine‐2(1H)‐thiones: Versatile Precursors for Novel Pyrazolo[3,4‐b]pyridine,Thieno[2,3‐b]pyridines,and Their Fused Azines

Pyridine‐2(1H)‐thiones were prepared and reacted with several active halogenated reagents to afford novel thieno[2,3‐b]pyridines in excellent yields. Thieno[2,3‐b]pyridine‐2‐carbohydrazide derivative was prepared by the reaction of either ethyl 2‐((3‐cyanopyridin‐2‐yl)thio)acetate derivative or thieno[2,3‐b]pyridine‐2‐carboxylate derivative with hydrazine hydrate. On the other hand, the reaction of either pyridine‐2(1H)‐thione or ethyl 2‐((pyridin‐2‐yl)thio)acetate derivative with hydrazine hydrate afforded the corresponding 1H‐pyrazolo[3,4‐b]pyridine derivative. Thieno[2,3‐b]pyridine derivatives reacted with several reagents to afford the corresponding pyrimidine‐4(3H)‐ones and [1,2,3]triazin‐4‐(3H)‐one. Moreover, 2‐carbohydrazide derivative reacted with β‐dicarbonyl reagents to give 2‐((3‐methyl‐1H‐pyrazol‐1‐yl)carbonyl)thienopyridines. The structure of the target molecules is elucidated using elemental analyses and spectral data.     

Synthesis and cyclopolymerization of novel allyl‐acrylate quaternary ammonium salts

Novel allyl‐acrylate quaternary ammonium salts were synthesized using two different methods. In the first (method 1), N,N‐dimethyl‐N‐2‐(ethoxycarbonyl)allyl allylammonium bromide and N,N‐dimethyl‐N‐2‐(tert‐butoxycarbonyl)allyl allylammonium bromide were formed by reacting tertiary amines with allyl bromide. The second (method 2) involved reacting N,N‐dialkyl‐N‐allylamine with either ethyl α‐chloromethyl acrylate (ECMA) or tert‐butyl α‐bromomethyl acrylate (TBBMA). The monomers obtained with the method 2 were N,N‐diethyl‐N‐2‐(ethoxycarbonyl)allyl allylammonium chloride, N,N‐diethyl‐N‐2‐(tert‐butoxycarbonyl)allyl allylammonium bromide, and N,N‐piperidyl‐N‐2‐(ethoxycarbonyl)allyl allylammonium chloride. Higher purity monomers were obtained with the method 2. Solution polymerizations with 2,2′‐azobis(2‐amidinopropane) dihydrochloride (V‐50) in water at 60–70°C gave soluble cyclopolymers which showed polyelectrolyte behavior in pure water. Intrinsic viscosities measured in 0.09M NaCl ranged from 0.45 to 2.45 dL/g. ¹H‐ and ¹³C‐NMR spectra indicated high cyclization efficiencies. The ester groups of the tert‐butyl polymer were hydrolyzed completely in acid to give a polymer with zwitterionic character. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 901–907, 1999     

Synthesis and Structure of Novel Thieno[2, 3‐d]Pyrimidine Derivatives Containing 1, 3, 4‐Oxadiazole Moiety

The reaction of 5‐(1‐pyrrolyl)‐4‐methyl‐2‐phenylthieno[2, 3‐d]pyrimidine carbohydrazide 5 with CS₂ in the presence of pyridine afforded the 6‐(2, 3‐dihydro‐2‐mercapto‐1, 3, 4‐oxadiazol‐5‐yl)‐4‐methyl‐5‐(1‐pyrrolyl)‐2‐phenylthieno[2, 3‐d]pyrimidine 6 , which reacted with methyl iodide in the presence of sodium methoxide to yield the 6‐(2‐methylthio‐1, 3, 4‐oxadiazol‐5‐yl)‐4‐methyl‐5‐(1‐pyrrolyl)‐2‐phenyl‐thieno[2, 3‐d]pyrimidine 7. The 6‐(2‐substituted‐1, 3, 4‐oxadiazol‐5‐yl)‐2‐phenylthieno[2, 3‐d]pyrimidine derivatives 9, 11 and 13 were obtained by the condensation of 6‐(2‐methylthio‐1, 3, 4‐oxadiazol‐5‐yl)‐2‐phenylthieno[2, 3‐d]pyrimidine 7 with appropriate secondary amines. The structure of the new compounds was substantiated from their IR, UV‐vis spectroscopy, ¹H NMR, mass spectra, elemental analysis and X‐ray crystal analysis.