氯化亚铜催化3-氯-1-丁烯异构为1-氯-2-丁烯研究

采用一价铜盐为催化剂、二甲基甲酰胺为溶剂,在均相体系中催化3-氯-1-丁烯异构化生成1-氯-2-丁烯.考察了溶剂、反应温度、催化剂种类和加入量对反应的影响,研究发现反应温度和催化剂的加入量对异构化反应有较大影响.在最优条件3-氯-1-丁烯1 mL,二甲基甲酰胺9 mL,CuCl 0.10 g,60℃反应5 h,产物和原料的浓度比为3.88 mmol L-1.采用在线红外光谱对反应过程进行监测,检测到有红外吸收峰在反应过程中先增加后减少的变化过程,提出了可能的反应机理.     

1-三氯锡烷基-2,3-丁二烯和2-三氯锡烷基-1,3-丁二烯与甲醛反应的B3LYP研究

用密度泛函方法在B3LYP/6-31G^**水平上研究了1-三氯锡烷基-2,3-丁二烯和2-三氯锡烷基-1,3-丁二烯与甲醛的反应.优化得到各驻点的几何构型,通过振动分析和内禀反应坐标对过渡态进行了确认,解析了反应路径.并用SCRF(PCM)方法在同一水平上对在CH₂Cl₂溶液中的两反应进行了研究.计算了两反应在气相和CH₂Cl₂溶液中的活化能垒、自由能和平衡常数.结果表明,反应具有很强的选择性,主要得到1-三氯锡烷基-2,3-丁二烯与甲醛反应的产物.该结果与实验事实一致.     

2-甲基-4-甲氧基苯基苯胺的合成

邻硝基甲苯在甲醇、乙酸和硫酸混合溶液中, 在Pt/C的催化下发生氢化和Bamberger重排生成2-甲基-4-甲氧基苯胺. 后者在Pd/C的存在下以苯酚为反应介质与环已酮缩合生成2-甲基-4-甲氧基苯基苯胺, 反应总产率63.0%. 文中给出了产物与中间产物的核磁共振氢谱和质谱, 同时讨论了影响反应的因素.     

2,3-二氯-5,6-二氰基-1,4-苯醌/NaNO2

设计了一种由 2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)和NaNO2组成的复合催化剂,该催化剂在9,10-二氢蒽氧化脱氢生成蒽的反应中表现出很高的催化活性和选择性. 在120 ℃和1.3 MPa O2下反应 8 h, 9,10-二氢蒽转化率达到99%以上,蒽的选择性为99%. 采用红外光谱和核磁共振方法对催化氧化脱氢的反应历程进行了研究. 结果表明, 9,10-二氢蒽氧气氧化脱氢生成蒽的反应是通过DDQ/DDQH2和NO2/NO两个氧化还原对的电子传递来推动的,以DDQ/NaNO2为催化剂可以有效催化9,10-二氢蒽氧化脱氢生成蒽.     

二-(2-羟基-5-长链烷基苯基)-甲烷的合成

以脂肪酸、苯酚为原料, 经酰化反应、酯化反应、Fries重排、黄鸣龙还原等步骤, 得到正构长链烷基酚, 再与多聚甲醛在酸性催化剂下进行缩合反应, 生成二-(2-羟基-5-长链烷基苯基)-甲烷, 用核磁共振氢谱和碳谱、红外光谱和元素分析对产物进行了结构鉴定. 据上述反应路线, 以工业品壬基酚和多聚甲醛为原料, 合成出了二-(2-羟基-5-壬基苯基)-甲烷, 并对其工艺条件进行了研究. 结果表明, 选用草酸作催化剂, 烷基酚和甲醛物质的量比为2∶1, 130 ℃反应4 h, 产物产率达到60%, 且反应转化率和选择性分别为63%和95%.     

超声波辐射条件下3-香豆素基-4-苯基-4,5-二氢-1,2,4-三唑-5-硫醚的合成

以香豆素-3-甲酰肼为原料,探讨了芳酰肼与异硫氰酸苯酯在超声波辐射条件下经环合反应生成1,2,4-三唑-5-硫酮的反应条件;进而借助1,2,4-三唑-5-硫酮的烷基化反应合成了两个含有硫醚结构的1,2,4-三唑衍生物.利用红外光谱和核磁共振谱表征了产物的结构,并利用元素分析测定了其组成.结果表明,与常规方法相比,超声波辐射条件下芳酰肼与异硫氰酸苯酯环合成1,2,4-三唑-5-硫酮的产率显著提高.     

从(-)-α-蒎烯合成(IR,3R)-(+)-反式菊酸甲酯

报道了以(-)-α-蒎烯为主要成分的松节油作原料,通过十四步反应合成了(1R,3R)-(+)-反式菊酸甲酯,每步反应的得率都在60%以上,总得率10.8%.反应操作方便,条件温和,对合成路线中的有些反应作了一些比较和讨论.化合物3-9都是新化合物.     

脯氨酸催化新型3-α,β-不饱和酮取代-4-羟基喹啉-2-酮简便合成及其荧光性质研究

3-乙酰-4-羟基喹啉-2-酮和芳香醛在L-脯氨酸有效催化下发生Aldol反应,生成一系列缩合产物3-α,β-不饱和酮取代-4-羟基喹啉-2-酮.该反应在甲醇溶液中进行,并且产物作为沉淀直接从溶液中析出,简单洗涤可得纯产物.研究表明芳香醛上的取代基性质对产物的产率有显著影响,其结果证实了该缩合反应经历了一个脱水中间体的反应历程.此外,对产物的荧光性质研究表明该类化合物可作为潜在应用价值的有机光学材料.     

1,4-二苯基-1,3-丁二烯的氰基蒽敏化光氧化反应

某些不能与单线态氧(~1O_2)起反应的烯烃、炔烃、硫醚和环氧化合物,在以氰基蒽为敏化剂的条件下,可发生经由光敏电子转移机理的氧化反应.近年来,Santamaria 等,Foote 等和我们都在研究这类反应.本文报道以9,10-二氰基蒽(DCA)为敏化剂、反,反-1,4-二苯基-1,3-丁二烯为反应物的电子转移光敏氧化反应,并讨论了反应机理.     

二[4-羟基-5,6-二氢-6-烷基(芳基)-2H-吡喃-2-酮-3-]烃的合成及生物活性的研究

采用5,6-二氢-6-烷基(芳基)-2H-吡喃-2,4-二酮和醛进行缩合反应,合成了二[4-羟基-5,6-二氢-6-烷基(芳基)-2H-吡喃-2-酮-3-]烃.其结构经¹HNMR和元素分析证实.对反应条件(反应温度、反应时间)进行了探讨.生物活性初步测定表明,该类化合物具有一定的杀菌和抗烟草花叶病毒的活性.     

Reductive cyclizations of hydroxysulfinyl ketones: enantioselective access to tetrahydropyran and tetrahydrofuran derivatives

The stereocontrolled formation of cis-2,5-disubstituted tetrahydrofurans and cis-2,6-disubstituted tetrahydropyrans is achieved from enantiopure ketosulfinyl esters by reduction, Weinreb's amide, and ketone formation, followed by the reductive cyclization (Et3SiH/TMSOTf) of the resulting hydroxysulfinyl ketones. The sulfoxide-bearing heterocycles were transformed into two natural products, (-)-centrolobine (1) and both enantiomers of cis-(6-methyltetrahydropyran-2-yl)acetic acid (2).     

Stereoselective synthesis of functionalized trans-2,5-disubstituted tetrahydrofurans

[reaction: see text] The addition of the titanium enolates of N-acetyl, N-propionyl, and N-bromoacetyl (R)-oxazolidin-2-ones to gamma-lactol 2, derived from (S)-glutamic acid, afforded trans- and cis-2,5-disubstituted tetrahydrofurans (trans/cis ratio: R = H, 2:1; R = Me, 8:1; R = Br, 10:1) after desilylation with aqueous HF/CH3CN. Chromatographic separation and LiBH4 reduction allowed the efficient preparation of the corresponding trans-2,5-disubstituted tetrahydrofuran diols and the recovery of the chiral auxiliary.     

Stereoselective synthesis of cis-2,5-disubstituted THFs: application to adjacent bis-THF cores of Annonaceous acetogenins

The iodocyclization of γ,δ-unsaturated alcohols in the presence of a silyl enol ether produced cis-2,5-disubstituted tetrahydrofurans in one pot via siloxy intermediates. N-Iodosuccinimide (NIS) effectively worked as an activator of the double bonds in the substrates and the silyl enol ether. Application to an expedient synthesis of the adjacent bis-tetrahydrofuran core of Annonaceous acetogenins with a cis/threo/cis relative stereochemistry is also described.     

Head-to-head polymers. XV. A facile synthesis of 2,3-disubstituted succinates and butanediols-1,4

A synthetic approach that makes symmetrically 2,3-dialkyl-substituted succinates and compounds prepared from 2,3-dialkyl-substituted succinates easily available has been developed. Coupling of α-bromoalkanoic esters with a zinc/copper couple produced in about 40% yield 2,3-disubstituted succinates which were reduced with LiAlH₄ to 2,3-disubstituted butanediols-1,4 in nearly quantitative yields. Some 2,3-disubstituted butanediols-1,4 were cyclodehydrated under reduced pressure with KHSO₄ to 3,4-disubstituted tetrahydrofurans or acetylated and the diacetyl compounds pyrolyzed at 525°C to 2,3 disubstituted butadienes-1,3. The length of the alkyl chains of the 2,3-dialkylsuccinates and consequently the 2,3-dialkylbutanediols-1,4 ranged from C₂ to C₁₆. 2,3-Disubstituted butanediols-1,4, 2,3-disubstituted butadienes-1,3, and 3,4-disubstituted tetrahydrofurans are interesting monomers for polymerization experiments.     

Highly diastereoselective synthesis of tetrahydrofurans via Lewis acid-catalyzed cyclopropane/aldehyde cycloadditions

A one-step procedure for the preparation of 2,5-disubstituted tetrahydrofurans from donor-acceptor cyclopropanes and aldehydes has been developed. In the presence of a catalytic amount of Sn(OTf)(2), cyclopropanes bearing an aryl or conjugated donor substituent vicinal to a malonyl diester group undergo cycloadditions with diverse conjugated aldehydes furnishing tetrahydrofurans with high cis diastereoselectivity. This method is useful for the preparation of regiodefined tetrahydrofurans.     

Stereoselective synthesis of 3,4-disubstituted tetrahydrofurans and 2,3,4-trisubstituted tetrahydrofurans using an intramolecular allylation strategy employing allylsilanes

A Brønsted acid-mediated intramolecular allylation involving an allylsilane and an aldehyde has been used as the key step in a stereoselective synthesis of 3,4-disubstituted tetrahydrofurans and 2,3,4-trisubstituted tetrahydrofurans.     

Scope and mechanism for lewis acid-catalyzed cycloadditions of aldehydes and donor-acceptor cyclopropanes: evidence for a stereospecific intimate ion pair pathway

In this work, the one-step diastereoselective synthesis of cis-2,5-disubstituted tetrahydrofurans via Lewis acid catalyzed [3 + 2] cycloadditions of donor-acceptor (D-A) cyclopropanes and aldehydes is described. The scope and limitations with respect to both reaction partners are provided. A detailed examination of the mechanism has been performed, including stereochemical analysis and electronic profiling of both reactants. Experimental evidence supports an unusual stereospecific intimate ion pair mechanism wherein the aldehyde functions as a nucleophile and malonate acts as the nucleofuge. The reaction proceeds with inversion at the cyclopropane donor site and allows absolute stereochemical information to be transferred to the products with high fidelity. The mechanism facilitates the stereospecific synthesis of a range of optically active tetrahydrofuran derivatives from enantioenriched D-A cyclopropanes.     

Stereoelectronic control in the solvolysis of spiroepoxidic 1-norbornyl triflates: unexpected reactivity in 3-bromomethyl derivatives

Interesting norbornane-fused tetrahydrofurans, with an additional synthetically-valuable vicinal dioxy-substitution in the norbornane skeleton, are enantiospecifically obtained in high yield from epimeric camphor-derived 3-endo-bromomethyl-substituted spiroepoxidic 1-norbornyl triflates. The process takes place via a domino reaction stereoelectronically controlled by the bromine atom. The described process has synthetic value, since it opens the way for a future enantiospecific preparation of 2,3-disubstituted tetrahydrofurans from camphor.     

Access to 2,5-disubstituted tetrahydrofurans from Grignard reagents and hemiacetal derivatives

The first diastereoselective addition of Grignard reagents onto cyclic oxocarbenium ions, obtained from glycosyl acetates, to afford 2,5-disubstituted tetrahydrofurans, is reported.     

Diastereoselective synthesis of 2,5-disubstituted tetrahydrofurans

This review focuses on synthetic methods allowing the preparation of 2,5-disubstituted tetrahydrofurans reported in the literature between 1993 and 2008.