催化量碘代烷烃促进下合成3,5-二取代异噁唑啉

研究了端基烯烃和醛肟在氧化剂过硫酸氢钾和催化量碘代烷烃作用下的[3+2]环合反应,合成了一系列具有良好产率及区域选择性的3,5-二取代异噁唑啉化合物.反应中,碘代烷烃先经过氧化分解产生了活泼的次碘酸,再依次与醛肟和烯烃经亲电加成反应生成五元杂环碘代中间体,该中间体通过消除反应得到3,5-二取代异噁唑啉化合物.考察了反应条件的影响,提出了可能的反应机理,为合成3,5-二取代异噁唑啉化合物提供了新方法.     

聚乙二醇支持的2,5-二取代异噁唑啉衍生物的液相合成

介绍了通过1,3-偶极环加成合成2,5-二取代异噁唑啉衍生物的液相合成方法, 利用聚乙二醇(PEG)支持的烯烃与由醛肟制得的腈氧化物反应制备了多种异噁唑啉衍生物, PEG解脱后产物的产率和纯度均很高.     

1-[3′-(4"-甲氧基苯基)-5′-甲基异噁唑-4′-甲酰基]-4-芳基氨基硫脲及其衍生物的合成

以3,5-二取代异噁唑-4-甲酰肼为基本原料制备关键中间体1-(3-对甲氧基苯基-5-甲基异噁唑-4-基)-4-芳基氨基硫脲(3a～3c);3在不同条件下经关环反应制得含有3,5-二取代异噁唑的2-芳氨基噻二唑(4a～4c),2-芳氨基噁二唑(5a～5c)和3-[3′-(4"-甲氧基苯基)-5′-甲基-异噁唑4′-基)-4-芳基-1,2,4-三唑-5-硫酮(6a～6c);6与碘甲(乙)烷反应合成了4-芳基-5-[3′-(4″-甲氧基苯基)-5′-甲基异噁唑-4′-基]-3-甲(乙)硫基-1,2,4-三唑(7a～8c),其结构经1H NMR,IR,MS和元素分析表征,其中4,5,7和8未见文献报道.     

1-[3’-(4″-甲氧基苯基)-5’-甲基异噁唑-4’-甲酰基]-4-芳基氨基硫脲及其衍生物的合成

以3,5-二取代异噁唑-4-甲酰肼为基本原料制备关键中间体1-(3-对甲氧基苯基-5-甲基异噁唑-4-基)-4-芳基氨基硫脲(3a～3c);3在不同条件下经关环反应制得含有3,5-二取代异噁唑的2-芳氨基噻二唑(4a～4c),2-芳氨基噁二唑(5a～5c)和3-[3’-(4″-甲氧基苯基)-5’-甲基-异噁唑-4’-基)-4-芳基-1,2,4-三唑-5-硫酮(6a～6c);6与碘甲(乙)烷反应合成了4-芳基-5-[3’-(4″-甲氧基苯基)-5’-甲基异噁唑-4’-基]-3-甲(乙)硫基-1,2,4-三唑(7a～8c),其结构经1H NMR,IR,MS和元素分析表征,其中4,5,7和8未见文献报道。     

芳香化合物在碘或碘化铵催化作用下的单溴代反应

研究了芳香化合物在碘或碘化铵催化作用下的单溴代选择性反应, 该反应是经过有机高价碘中间体进行的. 通过该反应, 富电子芳香化合物在碘或碘化铵催化作用下很容易与溴化钾、 间氯过氧苯甲酸、 对甲苯磺酸和少量苯的混合物发生反应, 常温下短时间内得到产率良好并具有区域选择性的单溴代芳香化合物. 考察了反应条件的影响, 提出了可能的反应机理, 为简单快速合成单溴代芳香化合物提供了新方法.     

烯酸在有机高价碘试剂催化下的氯代内酯化反应

研究了不饱和烯酸在有机高价碘催化剂和间氯过氧苯甲酸作用下与氯化锂的反应. 通过该反应, 4-戊烯酸等可在常温下短时间内得到良好产率的氯代γ-丁内酯化合物, 提供了简单快速合成氯代γ-丁内酯的新方法. 考察了反应条件的影响, 并提出了可能的反应机理.     

新型含1,2,3-三唑基[1,2,4](噁)二唑并[4,5-a][1,5]苯并硫氮杂卓化合物的合成

将1,2,3-三唑环结构及1,2,4-噁二唑环等多个药效团结构叠加到同一个硫氮杂卓分子中,为药理及生理活性研究提供较好的先导化合物.反应在三乙胺存在下,用2,4-二芳基-2,3-二氢-1,5-苯并硫氮杂卓与α-氯代-2-苯基-1,2,3-三唑基-4-甲醛肟在室温进行1,3-偶极环加成反应,合成一系列的2-苯基-1,2,3-三唑基[1,2,4]噁二唑并[4,5-a][1,5]苯并硫氮杂卓化合物,并采用红外光谱、核磁共振、元素分析等测试技术对化合物进行了表征.     

烯酸在碘化铵催化作用下的卤代内酯化反应

研究了不饱和烯酸在碘化铵催化作用下的溴代和氯代内酯化反应.通过该反应,4-戊烯酸等不饱和烯酸在催化剂碘化铵和氧化剂间氯过氧苯甲酸作用下很容易与溴化锂和氯化锂反应,常温下短时间内即可得到良好产率的溴/氯甲基γ-丁内酯化合物,从而建立了一个简单快速合成溴/氯甲基γ-丁内酯的新方法.考察了反应条件对反应的影响,提出了该反应是经过有机高价碘中间体而进行的反应机理.     

2-(ω-联苯基多亚甲基)-5-联苯基噁唑-1,3和2-(ω-联苯基多亚甲基)-5-联苯基噁二唑-1,3,4的合成

继2,6-二取代苯并二噁唑、2,5-二取代噁唑和2,5-二取代噁二唑及1,4-二(苯并噁唑-1,3基-2)苯等系列化合物合成及光性能研究后,又合成了双荧光发色团化合物2-(ω-联苯基多亚甲基)-5-联苯基噁唑-1,3和2-(ω-联苯基多亚甲基)-5-联苯基噁二唑-1,3,4共七种化合物。     

新型含1,2,3-三唑基[1,2,4]噁二唑并[4,5-a][1,5]苯并硫氮杂卓化合物的合成

将1,2,3-三唑环结构及1,2,4-噁二唑环等多个药效团结构叠加到同一个硫氮杂卓分子中,为药理及生理活性研究提供较好的先导化合物。反应在三乙胺存在下,用2,4-二芳基－2,3－二氢－1,5-苯并硫氮杂卓与α-氯代-2－苯基－1,2,3-三唑基4－甲醛肟在室温进行1,3-偶极环加成反应,合成一系列的2－苯基－1,2,3-三唑基[1,2,4]噁二唑并[4,5－a][1,5]苯并硫氮杂卓化合物,并采用红外光谱、核磁共振、元素分析等测试技术对化合物进行了表征。     

Synthesis of isoxazoles by hypervalent iodine-induced cycloaddition of nitrile oxides to alkynes

Treatment of oximes with hypervalent iodine leads to substituted isoxazoles via rapid formation of nitrile oxides. Reaction with terminal alkynes led to a series of 3,5-disubstituted isoxazoles with complete regioselectivity and high yield, in a procedure mild enough to prepare a range of nucleoside and peptide conjugates. Exceptionally high reaction rates were found for the formation of 3,4,5-trisubstituted isoxazoles from a cyclic alkyne.     

A Facile One‐Pot Synthesis of 3,5‐Disubstituted Isoxazole Derivatives Using Hydroxy (Tosyloxy) Iodobenzene

Hydroxy (tosyloxy) iodobenzene (HTIB), a hypervalent iodine reagent, has been extensively used for oxidative transformations. We have developed a one‐pot synthesis wherein aldoximes when reacted with alkynes in the presence of HTIB result in the direct formation of isoxazoles. This simple and straightforward reaction allows for ease of purification while leading to the formation of high purity 3,5‐disubstituted isoxazoles in moderate yields.     

N-heterocyclic carbene-catalyzed 1,3-dipolar cycloaddition reactions: a facile synthesis of 3,5-di- and 3,4,5-trisubstituted isoxazoles

A first example of organo-N-heterocyclic carbene (NHC) catalyzed click-type fast 1,3-dipolar cycloaddition of nitrile oxides with alkynes was developed for the regioselective synthesis of 3,5-di- and 3,4,5-trisubstituted isoxazoles. Triethylamine (Et(3)N) was employed as an effective base to generate both nitrile oxide and the organo-NHC catalyst in situ. This catalytic approach was used to attach a variety of substituents, including other biologically active fragments, onto the isoxazole ring to selectively design multinucleus structures. Further, we have also optimized the conditions for Cu(I)-free Sonogashira cross-coupling to obtain internal alkynes in high yields, which were subsequently used in cycloaddition. A catalytic cycle is proposed and the remarkable regiocontrol in the formation of isoxazoles was ascribed to a beneficial zwitterion intermediate developed by the interaction of the strongly nucleophilic organo-NHC catalyst with alkyne followed by nitrile oxide.     

Hypervalent Iodine–Catalyzed Cycloaddition of Nitrile Oxides to Alkenes

A new and convenient method for preparation of isoxazolines was developed by a catalytic cycloaddition of nitrile oxides generated in situ from aldoximes to alkenes in the presence of a catalytic amount of iodobenzene. In this protocol, iodobenzene was first oxidized into the hypervalent iodine intermediate by m-chloroperbenzoic acid, which then transformed aldoximes into nitrile oxides, and a 1,3-dipolar cycloaddition of nitrile oxides to alkenes to provide the isoxazolines in moderate to good yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Isoxazoles from 1,1-Disubstituted Bromoalkenes

The regioselective synthesis of 3,5-disubstituted isoxazoles was achieved through the 1,3-dipolar cycloaddition of nitrile oxides with 1,1-disubstituted bromoalkenes. The substituted bromoalkenes function as alkyne synthons which were used to construct 5,5-disubstituted bromoisoxazoline intermediates that aromatize to the analogous isoxazoles through the loss of HBr.     

Copper-doped silica cuprous sulfate (CDSCS) as a highly efficient heterogeneous nano catalyst for synthesis of 3,5-disubstituted isoxazoles

A facile and highly efficient protocol for 1,3-dipolar cycloaddition of in situ generated nitrile oxides with terminal alkynes catalyzed by copper-doped silica cuprous sulfate (CDSCS) as a new and convenient heterogeneous nano catalyst is described. In this protocol, ‘click’ cycloaddition of various structurally diverse alkynes and imidoyl chlorides in the presence of CDSCS and NaHCO₃ in a solution of i-PrOH/H₂O (1:1, V/V) furnishes the corresponding 3,5-disubstituted isoxazoles in good to excellent yields at room temperature. CDSCS was approved as a chemically and thermally stable nano catalyst that can be recovered and reused for many consecutive trials without considerable decline in its reactivity.     

An environmentally benign synthesis of isoxazolines and isoxazoles mediated by potassium chloride in water

An effective and environmentally benign procedure for the synthesis of isoxazolines and isoxazoles has been developed by a cycloaddition of nitrile oxides with alkenes or alkynes in water. In this approach, potassium chloride is first oxidized into chlorine in water by the environmentally friendly oxidant Oxone®, then aldoximes are oxidized into nitrile oxides by the in situ generated hypochlorous acid, finally a 1,3-dipolar cycloaddition between nitrile oxides and alkenes or alkynes occurs to provide the corresponding isoxazolines and isoxazoles in good yields.     

Copper-catalysed synthesis of 3,5-disubstituted isoxazoles enabled by pyridinyl benzimidazol (PBI) as a bidentate <Emphasis Type="Italic">N</Emphasis>-chelating ligand under mild conditions

In this paper, we introduced pyridinyl benzimidazol (PBI) as an easy-to-handle and bidentate N-chelating ligand that promote clean synthesis of 3,5-disubstituted isoxazoles in the presence of copper acetate as catalyst. This catalytic approach initiates with the hydroxyamination of aldehydes followed by chlorination and then generation of nitrile oxide which subsequently undergoes click-type [3 + 2]-dipolar cycloaddition with alkynes to give isoxazoles. This method provides an alternative green process to construct isoxazole derivatives.     

An environmentally benign benzylic oxidation catalyzed by hypervalent iodine intermediate in water

An effective and environmentally benign benzylic oxidation for transition of alkylarenes into the corresponding carbonyl compounds was reported.Alkylarenes were mixed and stirred with potassium bromide,m-chloroperbenzoic acid and a catalytic amount of iodobenzene in water at 60 8C for several hours,a series of the corresponding carbonyl compounds was obtained in moderate to good yields.In the reaction,iodobenzene was first oxidized by m-chloroperbenzoic acid into the hypervalent iodine intermediate which then reacted with potassium bromide to form the key radical initiator for the benzylic oxidation.