Synthesis,Characterization, and Antioxidant Evaluation of Some Novel Pyrazolo[3,4‐c][1,2]diazepine and Pyrazolo[3,4‐c]pyrazole Derivatives

5‐Hydrazineyl‐3‐methyl‐1H‐pyrazole ( 1 ) was used as a starting material for the synthesis of novel pyrazolo[3,4‐c][1,2]diazepine derivatives 3 , 4 , and 6a,b by its reaction with acetylacetone, ethyl acetoacetate, and isatylidene derivatives 5a,b , respectively. Also, pyrazolo[3,4‐c][1,2]diazepine derivative 11 was synthesized via multicomponent reaction of 1 , benzaldehyde, and malononitrile. Moreover, compound 1 was used for synthesis novel pyrazolo[3,4‐c]pyrazole derivative 7 by its reaction with isatin. In addition, pyrazolo[3,4‐c]pyrazole derivatives 18a–c were synthesized by treatment of 2‐cyano‐N′‐(3‐methyl‐1H‐pyrazol‐5‐yl)acetohydrazide ( 13 ) with aromatic aldehydes 16a–c . The newly synthesized compounds were valeted by means of analytical and spectral data. All newly synthesized compounds were screened for their antioxidant activities. Compounds 3 , 13 , 18b , and 18c showed higher radical‐scavenging activities.     

The synthesis of some pyrano[2,3-g]chromene-2,7-diones and furo[2,3-g]chromen-6-ones

The o-hydroxyformylcoumarin 5b , easily prepared from compound 1 , is further transformed to the title coumarin derivatives 7, 10, 19a-c via its initial Wittig olefination with ylides 2b, 8, 18a-c respectively. Coumarins 16a, b were also formed by treatment of 5b with compounds 15a, b . The preparation of the interesting furocoumarin derivatives 11, 14, 20b, c as well as of compound 13 is also described.     

Bis(α‐bromo ketones): Versatile Precursors for Novel Bis(s‐triazolo[3,4‐b][1,3,4]thiadiazines) and Bis(thiazoles)

A synthesis of novel bis(s‐triazolo[3,4‐b][1,3,4]thiadiazines) 4 , 5 , 6 in which the triazolothiadiazine is linked to the benzene core through the thiadiazine ring via phenoxymethyl spacers was reported. First attempt to synthesize 4 , 5 , 6 by the reaction of the appropriate bis(acetophenones) with 4‐amino‐3‐mercapto‐1,2,4‐triazole derivatives using an acidified acetic acid method were unsuccessful. On the other hand, reaction of the corresponding bis(α‐bromoketones) with 4‐amino‐3‐mercapto‐1,2,4‐triazole derivatives afforded 4 , 5 , 6 in good yields. The reaction pathway is assumed to involve S‐alkylation to give bis(aminotriazole) intermediates, followed by intramolecular cyclocondensation to give 4 , 5 , 6 . The successful isolation of the corresponding bis(aminotriazole) intermediates provides strong evidence for the proposed mechanism. The novel bis(thiazoles) 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , linked to alkyl or aryl spacers can also be synthesized by reaction of the appropriate bis(bromoacetyl) compounds 12a , 12b , 12c and 14 , 15 , 16 , 17 , 18 , 19 with the corresponding thioamide derivatives 20 , 21 , 22 .     

Einfache Synthese von 6-[4-Methyl-3-cyclohexen-1-yl]-hept-5-en-2-on,einer Vorstufe für α-Bisabolen und dessen Isopropenyl-Isomers. Terpene und Terpen-Derivate, 10. Mitteilung

Simple Synthesis of 6-[4-Methyl-3-cyclohexen-1-yl]-5-hepten-2-on, a Precursor of α-Bisabolene and Its Isopropenyl Isomer The alcohol 14 reacts with vinyl resp isopropenyl ether by Claisen rearrangement to give the aldehyde 16/17 resp. the ketone 3/4. Contrary to other reports this separable (E/Z)-mixture also occurs as a result of the synthesis following the pathway 7 → 8/9 → 10/11 → 12/13 (see also [2]). The bisabolene isomers 5 resp. 6 are obtained by reaction of 3 resp. 4 with methylidene triphenyl phosphorane. A mixture of 1 and 5. however, is formed from 3 via the alcohol 18 and its acetate 19. Likewise 4 reacts via 20 and 21 to give a (2/6) -mixture.     

Oligonucleosides with a Nucleobase‐Including Backbone,Part 4, A Convergent Synthesis of Ethynediyl‐Linked Adenosine Tetramers

Deprotection of the tetramer 24 , obtained by coupling the iodinated dimer 18 with the alkyne 23 gave the 8′,5‐ethynediyl‐linked adenosine‐derived tetramer 27 (Scheme 3). As direct iodination of C(5′)‐ethynylated adenosine derivatives failed, we prepared 18 via the 8‐amino derivative 17 that was available by coupling the imine 15 with the iodide 7 ; 15 , in its turn, was obtained from the 8‐chloro derivative 12 via the 4‐methoxybenzylamine 14 (Scheme 2). This method for the introduction of the 8‐iodo substituent was worked out with the N‐benzoyladenosine 1 that was transformed into the azide 2 by lithiation and treatment with tosyl azide (Scheme 1). Reduction of 2 led to the amine 3 that was transformed into 7 . 1,3‐Dipolar cycloaddition of 3 and (trimethylsilyl)acetylene gave 6 . The 8‐substituted derivatives 4a – d were prepared similarly to 2 , but could not be transformed into 7 . The known chloride 8 was transformed into the iodide 11 via the amines 9 and 10 . The amines 3 , 10 , and 16 form more or less completely persistent intramolecular C(8)N−H⋅⋅⋅O(5′) H‐bonds, while the dimeric amine 17 forms a ca. 50% persistent H‐bond. There is no UV evidence for a base‐base interaction in the protected and deprotected dimers and tetramers.     

A Novel Synthetic Approach to (±)‐Desoxynoreseroline

(±)‐Desoxynoreseroline ( 3 ), the basic ring structure of the pharmacologically active alkaloid physostigmine ( 1 ), was synthesized starting from 3‐allyl‐1,3‐dimethyloxindole ( 9 ). The latter was prepared from the corresponding 2H‐azirin‐3‐amine 6 by a BF₃‐catalyzed ring enlargement via an amidinium intermediate 7 (Scheme 1). An alternative synthesis of 9 was also carried out by the reaction of N‐methylaniline with 2‐bromopropanoyl bromide ( 12 ), followed by intramolecular Friedel–Crafts alkylation of the formed anilide 13 to give Julian's oxindole 11 . Further alkylation of 11 with allyl bromide in the presence of LDA gave 9 in an excellent yield (Scheme 3). Ozonolysis of 9 , followed by mild reduction with (EtO)₃P, gave the aldehyde 14 , whose structure was chemically established by the transformation to the corresponding acetal 15 (Scheme 4). Condensation of 14 with hydroxylamine and hydrazine derivatives, respectively, gave the corresponding imine derivatives 16a – 16d as a mixture of syn‐ and anti‐isomers. Reduction of this mixture with LiAlH₄ proceeded by loss of ROH or RNH₂ to give racemic 3 (Scheme 5).     

Bemerkungen zur Synthese von 3-Aminotoluol-5-sulfonsäure und 2-Aminotoluol-3-sulfonsäure

Some comments on the synthesis of 3-aminotoluene-5-sulfonic acid and 2-aminotoluene-3-sulfonic acid. Sulfonation of 3-nitrotoluene ( 5 ) yields predominantly the unsymetrical isomer 5-nitrotoluene-2-sulfonic acid ( 7 ), and lesser amounts of 5-nitrotoluene-3-sulfonic acid ( 6 ), previously reported as the major product. The desired 5-aminotoluene-3-sulfonic acid ( 3 ) was synthesized in preparative amounts from 6-aminotoluene-3-sulfonic acid (4) via the following sequence of reactions: diazotation and Sandmeyer replacement of 6-chlorotoluene-3-sulfonic acid ( 13 ), nitration of the sulfonyl chloride 14 under suitable conditions to give isomer free 6-chloro-5-nitrotoluene-3-sulfonyl chloride ( 15 ), hydrolysis to the sulfonic acid 16 and finally, simultaneous hydrogenolysis and reduction to 3 . The isomeric 7 was unequivocally prepared from 2-amino-5-nitrotoluene ( 9 ) via two routes: (1) diazotation, Sandmeyer thiocyanatation to 5-nitro-2-thiocyanatotoluene ( 10 ), Na₂S reduction to the di(2-methyl-4-nitro-phenyl)-disulfide ( 11 ), treatment with nitric acid and chlorine to give 5-nitrotoluene-2-sulfonyl chloride ( 12 ) and finally alkaline hydrolysis to 7 ; (2) Meerwein's SO₂ treatment of the diazonium salt derived from 9 leads directly to 12 and thence to 7 . 2-Aminotoluene-3-sulfonic acid ( 1 ) was prepared from the key intermediate 3-amino-2-nitrotoluene ( 18 ) via the same two routes used to prepare 7 from 9 . Both reaction sequences provided 2-nitrotoluene-3-sulfonly chloride, the hydrolysis product of which was reduced to 1 . Intermediate 18 was prepared in the following four steps from m-toluic acid ( 19 ): nitration to the 2-nitroderivative ( 20 ), whose acid chloride ( 21 ) was converted to 2-nitro-m-toluamide ( 22 ), and Hoffmann rearrangement to 18 .     

Photochemical Cyclization of Allylated Anisole and N-Alkyl Aniline Derivatives. Preliminary communication

The allyl anisole derivatives 1 , d₂- 1 , 3 , 5 and 7 (Scheme 1), on exposure to UV. light in benzene, acetone or methanol solution, cyclize to yield the corresponding cyclopropyl anisole derivatives 2 , d₂- 2 , cis- and trans- 4, 6 and 8 , respectively. Under the above conditions the N, N-dialkyl-2-allyl anilines 9 , 10 and 11 give similar results (Scheme 2). On the other hand, N-alkyl-2-allyl anilines ( 15 and 19 , Scheme 3) are transformed by UV. light in cyclohexane or benzene solution into 2-methyl-indolines ( 16 and 20 , resp.), whereas in methanol solution the corresponding 2′-methoxy compounds 18 and 21 are formed in addition to 16 and 20 , respectively.     

A cyclopropenone route to new pyrrolizidine derivatives

New pyrrolizidine derivatives 6 and 7 were prepared from the 1, 5-dihydro-2H-pyrrol-2-one 3a via an acidic intramolecular aldol condensation in 16% and 42% yields, respectively. Compound 6 was obtained by dehydration of 7 with p-toluenessulfonic acid in 67% yield.     

Heterocyclic β-Enamino esters. 28. The reaction of heterocyclic β-Enamino esters and nitriles with cyclic amidines. A simple route to azolopyrimidines

Whereas 2-amino-3-ethoxycarbonyl-4,5-dihydrofurans Ia-c condense with 5-membered amidine derivatives, via elimination of ethanol to afford the azolopyrimidines IIIa,b, XI, and XIVa,b, the 2-amino-3-cyano-4,5-dihydrofurans Id,e give with the same reagents, under elimination of ammonia, the novel ring systems of furo-azolopyrimidines XVIII and XXa,b. 2-Amino-3-ethoxycarbonyl-5,6-dihydro-4H-thiopyrane (XXI) reacts with 5-amino-1,2,4-triazole (II) to yield the triazolo[1,5-a]pyrimidine XXII, and with 2-aminobenzimidazole to XXIII. The mechanism of these reactions is discussed. XIVb and VIIb are cyclized in a secondary step to give the novel furo[2,3-d]benzimidazo[1,2-a]pyrimidine XXVI, and furo[2,3-d]-1,2,4-triazolo[1,5-a]pyrimidine XXVIII respectively, besides the acetoxy derivatives XVII and XXIX.     

Diazo-Transfer Reaction with Diphenyl Phosphorazidate

Diphenyl phosphorazidate (DPPA) was used as the azide source in a one-pot synthesis of 2,2-disubstituted 3-amino-2H-azirines 1 (Scheme 1). The reaction with lithium enolates of amides of type 2 , bearing two substituents at C(2), proceeded smoothly in THF at 0°; keteniminium azides C and azidoenamines D are likely intermediates. Under analogous reaction conditions, DPPA and amides of type 3 with only one substituent at C(2) gave 2-diazoamides 5 in fair-to-good yield (Scheme 2). The corresponding 2-diazo derivatives 6–8 were formed in low yield by treatment of the lithium enolates of N,N-dimethyl-2-phenylacetamide, methyl 2-phenylacetate, and benzyl phenyl ketone, respectively, with DPPA. Thermolysis of 2-diazo-N-methyl-N-phenylcarboxamides 5a and 5b yielded 3-substituted 1,3-dihydro-N-methyl-2H-indol-2-ones 9a and 9b , respectively (Scheme 3). The diazo compounds 5–8 reacted with 1,3-thiazole-5 (4H)-thiones 10 and thiobenzophenone ( 13 ) to give 6-oxa-1,9-dithia-3-azaspiro[4.4]nona-2,7-dienes 11 (Scheme 4) and thiirane-2-carboxylic acid derivatives 14 (Scheme 5), respectively. In analogy to previously described reactions, a mechanism via 1,3-dipolar cycloaddition, leading to 2,5-dihydro-1,3,4-thiadiazoles, and elimination of N₂ to give the ‘thiocarbonyl ylides’ of type H or K is proposed. These dipolar intermediates with a conjugated C?O group then undergo either a 1,5-dipolar electrocyclization to give spirohetrocycles 11 or a 1,3-dipolar electrocyclization to thiiranes 14 .     

Synthesis and Reactions of Some New Benzo[a]phenothiazine‐3,4‐dione Derivatives

The reaction of 2,3‐dihydro‐2,3‐epoxy‐1,4‐naphthoquinone ( 4 ) with substituted anilines furnished the corresponding benzo[fused]heterocyclic derivatives 5 , 6 , 6a , 6b , 7 , 8 . Furthermore, treatment of benzo[a]phenothiazine derivative 7 with halo compounds, namely, ethyl bromoacetate, phenacyl bromide, dibromoethane, or chloroacetone afforded ether derivatives 11 , 12 , 13 , 14 , respectively. Moreover, the reaction of 11 with o‐substituted aniline gave the corresponding benzo[a]phenothiazin‐5‐one derivatives 15 , 16 , 17 and benzo[d][1,3]oxazin‐4‐one 18 , respectively. Finally, the chromenone derivative 19 was synthesized via the reaction of ester derivative 11 with salicyaldhyde in refluxing pyridine. The newly synthesized compounds were characterized by spectroscopic measurements (IR, ¹H NMR, ¹³C NMR, and mass spectra).     

Synthesis of (5′S)‐5′‐C‐Alkyl‐2′‐deoxynucleosides

We describe the synthesis of (5′S)‐5′‐C‐butylthymidine ( 5a ), of the (5′S)‐5′‐C‐butyl‐ and the (5′S)‐5′‐C‐isopentyl derivatives 16a and 16b of 2′‐deoxy‐5‐methylcytidine, as well as of the corresponding cyanoethyl phosphoramidites 9a , b and 14a , b , respectively. Starting from thymidin‐5′‐al 1 , the alkyl chain at C(5′) is introduced via Wittig chemistry to selectively yield the (Z)‐olefin derivatives 3a and 3b (Scheme 2). The secondary OH function at C(5′) is then introduced by epoxidation followed by regioselective reduction of the epoxy derivatives 4a and 4b with diisobutylaluminium hydride. In the latter step, a kinetic resolution of the diastereoisomer mixture 4a and 4b occurs, yielding the alkylated nucleoside 2a and 2b , respectively, with (5′S)‐configuration in high diastereoisomer purity (de=94%). The corresponding 2′‐deoxy‐5‐methylcytidine derivatives are obtained from the protected 5′‐alkylated thymidine derivatives 7a and 7b via known base interconversion processes in excellent yields (Scheme 3). Application of the same strategy to the purine nucleoside 2′‐deoxyadenine to obtain 5′‐C‐butyl‐2′‐deoxyadenosine 25 proved to be difficult due to the sensitivity of the purine base to hydride‐based reducing agents (Scheme 4).     

Bildung tricyclischer Thietan-Derivate durch intramolekulare(2+2)-Cycloaddition

Formation of Thietane Derivatives via Intramolecular (2+2) Cycloaddition On irradiation, the two 4-vinyl-1,3-thiazole-5(4H)-thiones 1a, b , synthesized from thiobenzoic acid and the corresponding 3-amino-2H-azirines 2a , b , undergo an intramolecular (2+2)-cycloaddition reaction of the C?S and C?C bonds to give the tricyclic thietane derivatives 3a , b .     

Synthesis of New Heterocyclic Compounds Using 2‐(3,3‐dimethyl‐1H‐pyrroloisoquinolin‐2(3H)‐ylidene)malonaldehydes

Isoquinolin‐5‐ylhydrazinium chloride 13 and 5‐bromoisoquinolin‐8‐ylhydrazinium chloride 14 were converted via Fischer syntheses with 3‐methylbutan‐2‐one into indolenines, 2,3,3‐trimethyl‐3H‐pyrrolo[2,3‐f]isoquinoline 15 and 5‐bromo‐2,3,3‐trimethyl‐3H‐pyrrolo[3,2‐h]isoquinoline 16 , respectively. Exposure of the indolenines to the Vilsmeier reagent produced diformyl compounds 17 and 18 , which reacted with arylhydrazines to give the corresponding pyrazoles 19a , 19b , 19c , 19d , 19e , 19f , 19g , 19h , 19i and 20a , 20b , 20c , 20d , 20e , 20f , 20g . Reaction of 17 with thiourea gave a pyrimidine‐2(1H)‐thione 23 or with hydroxylamine hydrochloride, an isoxazole 24 .     

Synthesis and Structure of 2‐Substituted Thieno[3′,2′:5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐one Derivatives

A series of new 2‐substituted 3‐(4‐chlorophenyl)‐5,8,9‐trimethylthieno[3′,2′: 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐ones 8 were synthesized via an aza‐Wittig reaction. Phosphoranylideneamino derivatives 6a or 6b reacted with 4‐chlorophenyl isocyanate to give carbodiimide derivatives 7a or 7b , respectively, which were further treated with amines or phenols to give compounds 8 in the presence of a catalytic amount of EtONa or K₂CO₃. The structure of 2‐(4‐chlorophenoxy)‐3‐(4‐chlorophenyl)‐5,8,9‐trimethylthieno[3′,2′: 5,6]pyrido[4,3‐d]pyrimidin‐4(3H)‐one ( 8j ) was comfirmed by X‐ray analysis.     

Umsetzungen von 1,3-Thiazol-5(4H)-thionen mit Grignard- und Organolithium-Verbindungen: Carbophile und Thiophile Additionen

Reactions of 1,3-Thiazole-5(4H)-thiones with Grignard- and Organolithium Compounds: Carbophilic and Thiophilic Additions Organolithium compounds and 1,3-thiazole-5(4H)-thiones 9 reacted via thiophilic addition on the exocyclic S-atom. The intermediate anion E has been trapped by protonation to give 12 and by alkylation to yield 16 , respectively (Schemes 5 and 6). In competition with protonation of E , a fragmentation to benzonitrile and a dithioester 14 was observed (Scheme 5). In some cases, the alkylation of E led to the formation of dithioacetals 17 instead of 16 (Scheme 6). Methyl, ethyl, and isopropyl Grignard reagents and 9 in THF underwent again a thiophilic addition yielding 4,5-dihydro-1,3-thiazoles of type 12 (Scheme 3). In contrast to this result, MeMgI reacted with 9a in Et₂O via carbophilic addition to 11 . Again a carbophilic attack at C(5) of 9 was observed with allylmagnesium and 2-propynylmagnesium bromide, respectively, in Et₂O.     

Synthesis of isocoumarin, 1-isoquinolone and 4(1H)-quinolone derivatives via seleno-intermediates

The reaction of 2-styrylbenzoic acids 2 with N-phenylselenosuccinimide (N-PSS) affords 3-phenyl-iso-coumarin derivatives 3 and 3,4-dihydro-3-phenyl-4-(phenylseleno)isocoumarins 4 via selenolactonization. The reaction of 2-styrylbenzamides 5 and 1-(2-aminophenyl)-3-phenyl-2-peropen-1-one derivatives 11 with N-PSS also resulted in the formation of 1-isoquinolone 6 and 4(1H)-quinolone derivatives 12 , respectively.     

1,3‐Dipolar Cycloadditions to (5Z)‐1‐Acyl‐5‐(cyanomethylidene)‐ imidazolidine‐2,4‐diones: Synthesis and Transformations of Spirohydantoin Derivatives

Cycloadditions of various 1,3‐dipoles to (5Z)‐1‐acyl‐5‐(cyanomethylidene)‐3‐methylimidazolidine‐2,4‐diones 8 or 9 , prepared in 3 steps from hydantoin ( 1 ) (Schemes 1 and 2), were studied. In all cases, reactions proceeded regio‐ and stereoselectively. The type of product depended on the 1,3‐dipole and/or dipolarophile employed as well as on reaction conditions. Thus, with stable dipoles under neutral conditions, spirohydantoin derivatives 12 – 16 were obtained (Scheme 2), while under basic or acidic conditions, pyrazole‐ or isoxazole‐5‐carboxamides 18 and 23 – 26 and carboxylate 27 were formed via aromatization of the newly formed dihydroazole ring, followed by the simultaneous cleavage of the hydantoin ring (Schemes 3 – 5).     

Amino acids in the synthesis of heterocyclic systems. Synthesis of γ-(5-(1,2,4-Triazinylidene))-α,β-dehydro-α-amino acid derivatives and 6H-pyrido[1,2-d][1,2,4]triazin-6-ones

5-(1,2,4-Triazinyl) substituted enamines 3 react with 5(4H)-oxazolones 4 in acetic anhydride to give acetylated products 5 , while in toluene-acetic acid mixture nonacetylated products 9 are formed. Both types of products were isolated as (E,Z) mixtures. Compounds 5 and 9 rearrange into 6H-pyrido[1,2-d]-[1,2,4]triazin-6-ones 12 by heating in formic acid or in xylene, respectively. Compounds 5 are transformed in the presence of nucleophiles, such as sodium alkoxides or sodium amides via anionic form 10 into corresponding esters 13 and amides 14 of γ-(5-(1,2,4-triazinylidene)) substituted derivatives of α-amino-2-butenoic acid, which exist in 2-(Z),4-(Z) form.