A facile synthesis of 4-aryl-2H-1-benzopyran-2-ones

Reaction of 2-hydroxybenzophenones (1,3,7,8) with ethoxycarbonyl-methylenetriphenylphosphorane affords 4-aryl-2H-1-benzopyran-2-ones (2,4–6) in excellent yields.

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Eine einfache Synthese für 4-Aryl-2H-1-benzopyran-2-one

Zusammenfassung Die Reaktion der 2-Hydroxybenzophenone1,3,7 und8 mit Ethoxycarbonyl-methylentriphenylphosphoran ergab die 4-Aryl-2H-1-benzopyran-2-one2 und4–6 in ausgezeichneten Ausbeuten.

     

A facile synthesis of certain 4- and 4,5-disubstituted 1-β-d-ribofuranosylpyrazoles

A number of pyrazole ribonucleosides, structurally related to AICA riboside and ribavirin have been prepared and evaluated for their biological activity in vitro. Deisopropylidenation of 5-amino-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)pyrazole-4-carbonitrile ( 6 ) with aqueous trifluoroacetic acid gave 5-amino-1-(β-D-ribofuranosyl)pyrazole-4-carbonitrile ( 7 ). Conventional transformation of the carbonitrile function of 7 gave the AICA riboside congener ( 2 ) and related 5-amino-1-(β-D-ribofuranosyl)-pyrazoles ( 8–10 ). Acetylation of 7 at low temperature gave the versatile intermediate 5-amino-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazole-4-carbonitrile ( 15 ). Non-aqueous diazotization of 15 with isoamylnitrite in dibromomethane or diiodomethane gave the corresponding C₅-bromo 13 and C₅-iodo 16 derivatives. Compounds 13 and 16 were subsequently transformed into 5-bromo-1-(β-D-ribofuranosyl)pyrazole-4-carboxamide ( 11 ) and the 5-iodo analog 25 . However, a similar nonaqueous diazotization of 15 in dichloromethane afforded the deaminated product 1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazole-4-carbonitrile ( 22 ). Treatment of 22 with ammonium hydroxide/hydrogen peroxide gave the ribavirin congener 1-(β-D-ribofuranosyl)pyrazole-4-carboxamide ( 18 ). Similar treatment of 22 with hydrogen sulfide in pyridine or hydroxylamine in ethanol gave the 4-thiocarboxamide 19 and 4-carboxamidoxime 20 derivatives, respectively. Catalytic hydrogenation of 20 afforded 1[β-D-ribofuranosyl)pyrazole-4-carboxamidine ( 21 ). These pyrazole nucleosides are devoid of any significant antiviral or antitumor activity in vitro.     

吡咯烷类手性二胺配体N-烷基化物的简易合成法

吡咯烷类及有关的手性二胺配体通过使用氯化锌-多聚甲醛-硼氢化钾或硼氢化钠一锅煮反应进行烷基化,具有产率高、操作简易等优点。     

A facile synthesis of 2-(6-ethoxycarbonyl-2-cis-hexenyl)-4-hydroxy-2-cyclopentenone

The title compound $\text{1b}$, a key intermediate for PGE₂ elaboration, is readily available in nine steps from furfuryl alcohol. The crucial steps include the exclusive formation of $\text{6a}$ from $\text{5}$ and the subsequent intramolecular Aldol condensation to $\text{2b}$.     

A facile synthesis of methyl 2-substituted-4-benzoxazolecarboxylates

Methyl 2-substituted-4-benzoxazolecarboxylates were synthesized from methyl 2-amino-3-hydroxybenzoate and the corresponding acid chloride or ortho acetal with pyridinium p-toluenesulfonate as an acid catalyst. Decomposition due to hydration at the 2-position was seen for some compounds during purification.     

A facile synthesis of 2-(N-alkylamino)-pyrimidin-4-one derivatives

Substituted 2-(N-alkylamino)-pyrimidin-4-ones were synthesized from N-alkyl β-amino acid esters starting with guanidinylation using Pbf-activated thiourea. The six-membered pyrimidinones were obtained in good yields via intramolecular cyclization during TFA cleavage of the Pbf protecting group.     

An improved synthesis of 3-(1-imidazolyl)-2-alkenoic acid derivatives and related compounds

The preparative method of 3-(1-imidazolyl)-2-alkenoic acid derivatives and the related compounds was improved by the use of strong bases such as sodium hydride in DMF. By this improved method, the preparation of 2-substituted 3-(1-imidazolyl)-2-alkenoic acid derivatives was accomplished in good yields.     

1,5-naphthyridines. Synthesis of 7-chloro-4-(4-diethylamino-1-methylbutylamino)-2-methoxy-1,5-naphthyridine and related compounds

The synthesis of 7-chloro-4-(4-diethylamino-1-methylbutylamino)-2-methoxy-1,5-naphthyridine, a compound which incorporates the structure of both chloroquine (a schizontocidal drug) and pamaquine (a gametocytocidal drug), has been carried out. In addition, two structurally related derivatives, the, “5-azachloroquine” and the “5-azapamaquine,” have also been obtained by multi-step syntheses. “5-Azachloroquine” possesses good antimalarial activity against Plasmodium berghei. The compound was also found to be less toxic than the known 4-aminoquinoline and 8-aminoquinoline antimalarial drugs.     

A facile and highly stereoselective synthesis of (2E)-, (2E,4E)-unsaturated amides and related natural products

A facile synthesis of (2E)-, (2E, 4E)-unsaturated amides was achieved via arsonium bromides with high stereoselectivity. Its application to the synthesis of related natural products 4 and 5 is also reported.     

A facile synthesis of pyrimidin-4-ones

A facile synthesis of 2,6-disubstituted pyrimidin-4-ones and 2,5,6-trisubstituted pyrimidin-4-ones from commercially available materials with application of microwave technology in key steps is described.     

A facile one pot synthesis of 1-alkylbenzimidazoline-2-thiones

Reactions of benziraidazoline-2-thione with alkyl halides in the presence of sodium naphthalenide in tetra-hydrofuran at room temperature under a nitrogen atmosphere afforded 1-alkyl-2-alkylthiobenzimidazoles in excellent yields, which underwent a bond cleavage between S and C of alkyl group to give excellent yields of 1-alkylbenzimidazoline-2-thiones by the treatment with an additional amount of sodium naphthalenide.     

A facile synthesis of 2-substituted-4-(substituted)phenyl-Δ2-1,3,4-oxadiazolin-5-ones

The title compounds, 3, are formed at ambient temperature from 4,4-dimethyl-2-(substituted)-phenylsemicarbazides (1) and carboxylic acid chlorides in the presence of triethylamine. 2-Dimethylamino-4-(substiluted)phenyl-Δ²-1,3,4-oxadiazolin-5-ones are formed from 1 and dialkyl-carbamoyl chlorides at elevated temperature (about 15° ). Acylation of 1 with carboxylic acid anhydrides, also at elevated temperature, is accompanied by loss of dimethylamine from the intermediate l-acyl-4,4-dimethyl-2-(substituted)phenylsemicarbazides, 2, to give 3.     

1-(2'-苯基-1', 2', 3'-三唑-4'-甲酰基)-4-芳基氨基硫脲及其 环化产物的合 成

以2-苯基-1,2,3-三唑-4-甲酰肼为原料合成了几种新的1-(2'-苯基-1',2',3'-三唑-4'-甲酰基)-4-芳基氨基硫脲,在不同条件下环化,制得一系列新的1,3,4-噻二唑、1,3,4-恶二唑和1,2,4-均三唑衍生物。化合物的结构经元素分析、IR、^1HNMR和MS确证,并对其波谱性质进行了讨论。     

1-(2-Mercaptoethyl)phthalazines and related compounds

1-(2-Mercaptoethyl)phthalazine (VII) and its analogs such as S-2-(1-phthalazyl)ethyliso-thiuronium bromide (VI), sodium S-2-(1-phthalazyl)ethylthiosulfate (VIII), 1,3-bis-acetylthio-2-(1-phthalazyl)propane (XII), 2-(1-phthalazyl)-1,3-propanedithiol (XIII), disodium 2-(1-phthalazyl)-1,3-propanedithiosulfate (XIV), 3-dimethylamino-2-(1-phthalazyl)-1-propanethiol (XVII) and 3-(4-methyl-1-piperazinyl)-2-(1-phthalazyl)-1-propanethiol (XIX) have been prepared as potential radiation protection agents.