5-Bromomethyl-4,5-dihydroisoxazoles

The preparation of substituted 4,5-dihydroisoxazoles can be accomplished via the treatment of β,γ-unsaturated oximes with liquid bromine. The reaction provides a convenient route to the highly functionalized title compounds.     

Solid base-catalyzed synthesis of 5-substituted 4,5-dihydroisoxazoles

We present a new synthetic route for the preparation of 5-substituted 4,5-dihydroisoxazole derivatives starting from ethyl nitroacetate and alkenes in the presence of modified Mg:Al 3:1 hydrotalcite.     

Synthesis and Mesomorphic Properties of New 3-Aryl-5-cyano-4,5-dihydroisoxazoles

New 3-aryl-5-cyano-4,5-dihydroisoxazoles possessing liquid crystalline properties were synthesized in two ways. The key stage in both procedures is 1,3-dipolar cycloaddition of nitrile oxides to acrylonitrile.     

Haloacetylated enol ethers. 6 [5]. Synthesis of 4,5-trimethylene-4,5-dihydroisoxazoles

The investigation of the effect of the cyclopentane ring on the regiochemistry of the reactions of 2-acetylcyclopentanones 1a-d and β-methoxyvinyl trifluoromethyl ketone derivative 2a with hydroxylamine hydrochloride is reported. The reactions give regiospecifically the 4,5-trimethylene-4,5-dihydroisoxazoles 3a-d in good yields.     

Synthesis of 4-hydroxy-4,5-dihydro-1,2,4-triazol-5-ones

Summary A series of hydroxamic acid ethoxycarbonylhydrazides was obtained by reactions of ester ethoxycarbonylhydrazones with hydroxylamine. The corresponding 3-substituted 4-hydroxy-4,5-dihydro-1,2,4-triazol-5-ones were synthesized by cyclization of these hydroxamic acid derivatives in basic medium.

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Synthesen von 4-Hydroxy-4,5-dihydro-1,2,4-triazol-5-onen

Zusammenfassung Durch Reaktion von Esterethoxycarbonylhydrazonen und Hydroxylamin wurde eine Reihe von Hydroxamsäureethoxycarbonylhydraziden gewonnen; Cyclisierung dieser Verbindungen durch Base gab die entsprechenden 3-substituierten 4-Hydroxy-4,5-dihydro-1,2,4-triazol-5-one.

     

Synthesis of 4,5-decamethyleneimidazole, 4,5-decamethyleneoxazole, 4,5-decamethyleneisoxazole, 4,5-decamethyleneimidazolone-2, and 4,5-decamethylenepyrazole from cyclododecanone derivatives

4,5-Decamethyleneimidazole, 4,5-decamethyleneoxazole, and 4,5-decamethyleneimidazolone-2 were synthesized by reactions of 2-bromocyclododecanone and 2-hydroxycyclododecanone with formamide, ammonium formate, and urea, respectively. Condensation of 2-formylcyclododecanone with hydroxylamine and hydrazine hydrate resulted in 4,5-decamethyleneisoxazole, and 4,5-decamethylenepyrazole, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 891–893, May, 1994.     

4-芳亚甲基-4,5-二氢-1,3-二苯基吡唑-5-酮的一锅法合成

报道了以乙酸为催化剂,由苯甲酰乙酸乙酯、苯肼和芳香醛经三组分一锅法缩合制备4-芳亚甲基-4,5-二氢-1,3-二苯基吡唑-5-酮衍生物的新方法.该方法缩短了反应时间,得到了中等产率.产物结构经MS,1HNMR,IR和元素分析确证.     

Synthesis of 5-(thiazol-5-yl)-4,5-dihydroisoxazoles from 3-chloropentane-2,4-dione

Condensation of 3-chloropentane-2,4-dione with thioamides gives 1-(thiazol-5-yl)ethanones and subsequent Wittig olefination, followed by nitrile oxide 1,3-dipolar cycloaddition to the resulting prop-1-en-2-yl moiety, delivers racemic 5-(thiazol-5-yl)-4,5-dihydroisoxazoles. When this thiazole and isoxazoline diheterocyclic scaffold has a carboethoxy substituent at C2 of the thiazole ring, aminolysis provides for effective diversification. A 50-member library of various 5-(thiazol-5-yl)-4,5-dihydroisoxazoles is reported.     

Reactions of 1-Trichloromethyl-2,4,6-trimethylbenzene with 2-Amino- and 2-Amino-5-bromopyridines

A new type of reaction has been discovered for trichloromethylarenes with pyridines. The reaction of 1-trichloromethyl-2,4,6-trimethylbenzene with 2-amino- and 2-amino-5-bromopyridines does not stop with formation of the pyridinium salt, but rather leads to unique amidines, namely, 1-[-(2-pyridylimino)-2,4,6-trimethylbenzyl]-2-pyridonimine and its 5-bromo derivative.     

HZSM-5分子筛催化合成乙酰水杨酸——推荐一个半微量有机化学实验

设计了一个以水杨酸和乙酸酐为原料,以HZSM-5分子筛为催化剂,在室温或加热条件下高效合成乙酰水杨酸的半微量有机化学实验。与经典实验方法相比,新实验具有反应易于操作、产率高、污染小等优点,更符合绿色化学教学理念。     

Haloacetylated enol ethers. 7 . Synthesis of 3-aryl-5-trihalomethylisoxazoles and 3-aryl-5-hydroxy-5-trihalomethyl-4,5-dihydroisoxazoles

β-Aryl-β-methoxyvinyl trihalomethyl ketones 1a-g, 2a-g [aryl = p-YC₆H₄ where Y= H, Me, OMe, F, Cl, Br, NO₂] are cyclocondensed with hydroxylamine hydrochloride to afford the 3-aryl-5-hydroxy-5-trihalomethyl-4,5-dihydroisoxazoles 3a-g, 4a-f in good yield. The dehydratation of compounds 3a-g with concentrated sulfuric acid, led the corresponding 3-aryl-5-trichloromethylisoxazoles 5a-g . An alternative one-pot procedure yields 3-aryl-5-trihalomethylisoxazoles 5,6a-g directly by cyclocondesation of 1,2a-g with hydroxylamine hydrochloride in the presence of an excess of concentrated hydrochloric acid.     

Synthesis of 4,5-dihydroxyphthalonitrile

4,5-Dihydroxyphthalonitrile was synthesized from pyrocatechol in a simple way. The compound obtained is a convenient starting reagent for the preparation of 4,5-dialkoxyphthalonitriles.     

Complementary regioselective synthesis of 3,5-disubstituted isoxazoles from ynones

Two regioselective synthetic routes towards 3,5-disubstituted isoxazoles from ynones are reported. One route takes place via first converting the ynones to ynone O-methyl oximes, followed by a palladium-catalyzed intramolecular cyclization. The other involves the formation of 5-hydroxy-4,5-dihydroisoxazoles by a cyclocondensation between ynones and hydroxylamine, and subsequent acid mediated dehydration. The two routes are not only both highly regioselective, but also complementary to each other as a pair of regioisomeric 3,5-disubstituted isoxazoles are readily prepared from one single ynone substrate. The efficiency of the two routes are further evaluated and demonstrated in the synthesis of three representative 3,5-disubstituted isoxazoles.     

Synthesis and Antimicrobial Activity of Substituted 5-Cyano-6-oxo-2-styrylnicotinic Acids

Derivatives of the anilide or ethyl ester of 5-cyano-6-oxo-2-styrylnicotinic acid are formed in the reaction of the anilide or ethyl ester of 5-cyano-2-methyl-6-oxonicotinic acid with aromatic aldehydes. On interaction with hydrazine hydrate the products are converted into hydrazides of 5-cyano-6-oxo-2-styrylnicotinic acid derivatives.     

Synthesis and Antioxidant Activity Evaluation of Novel 5,7-dimethyl-3H-Thiazolo[4,5-B]Pyridines

Abstract

5,7-Dimethyl-3H-thiazolo[4,5-b]pyridine-2-one was obtained under the reaction of 4-iminothiazolidin-2-one with acetylacetone. Further structural modifications include the introduction of diversity at the N³ and C⁶ positions. The antioxidant activity of the synthesized compounds was evaluated in vitro by the method of scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures]     

Synthesis and Antimicrobial Activity of 2-Methyl-5-nitroaniline Derivatives:A Structure-Activity Relationship Study

A series of 2‐methyl‐5‐nitroaniline derivatives, 5a – 5k and 6a – 6f , were synthesized in order to determine their in vitro antimicrobial activity. The chemical structures of the synthesized compounds were confirmed by elemental analyses, UV‐visible, FT‐IR, ¹H NMR and ¹³C NMR spectral studies. The structure‐activity relationships of the synthesized compounds were also discussed. Among the synthesized compounds, 5f , 5d , 6b and 6e showed good antimicrobial activity compared to standard drugs.     

Synthesis and photoreactivity of some 5-alkylidene- and 5-alkylidenamine-2,5-dihydroisoxazoles

5-Alkylidene-2,5-dihydroisoxazoles and 5-alkylidenamine-2,5-dihydroisoxazoles were easily prepared from the corresponding 5-chloro-2-methylisoxazolium triflate and an enolizable compound or alkylamine. Their photochemical reactivity leads to photoisomers that in some cases constitute new heterocycles systems. The photorearrangement involves either triplet or singlet state depending on substituents and experimental conditions.