Chemoselective Bromodecarboxylation ofα-Carboxy-α-cinnamoyl Ketene Cyclic Dithioacetals

α-Oxoketene dithioacetals（ compound 1 ） are versatile synthons for organic synthesis due to their specially structural characteristic, that is, the masked ketene is conjugated with the convertible carbonyl in their molecules. Although there have been numerous reports covering the reactions in which they have been taken as 1,3-electrophiles, the reaction at the α-carbon atom of α-oxoketene dithioacetals has seldom been investigated. Junjappa and co-workers found the α- bromination of compound 2 in the presence of NBS led to α-aroyl-α-bromo ketenedithioacetals. However, the flexibility of the functional groups at the α-carbon atom of compound 2 are still limited.

Condensation Reaction of α-Aroyl-α-acetyl Ketene Cyclic Dithioacetals with Aromatic Aldehydes

The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.

A Convenient Synthesis of Pyrazolylpyrazoles Using α-Oxo Ketene S,S- and N,S-Acetals

Substituted pyrazolylpyrazoles were synthesized through the reaction of hydrazine hydrate and α-oxo-(3, 5-dimethyl-1 H-pyrazole-1-ly)ketene S, S- and N,S-Acetals which were obtained from α-oxo-(3,5-dimethyl-1 H-pyrazole-1-yl) acetophenone. Pyrazolylpyrazole was also prepared via α-oxo ketene N,O-acetal by way of ring chain transformation.

Azo-coupling Decarboxylation Reaction of α-Carboxy Ketene Dithioacetals in Water-a New Route to 1,2-Diaza-1,3-butadienes

Under basic conditions, a series of 4,4-dialkylthio-l,2-diaza-l,3-butadienes were synthesized in good to excellent yields via a novel azo-coupling decarboxylation reaction by reacting a-carboxyl ketene dithioacetals with aryldiazonium salts in aqueous medium.

STUDIES ON THE REACTIVITY OF CYCLOAROMATIZATION REACTION VIA a－OXO KETENE DITHIOACETALS

The dihydric dithioketenes 3a-c obtained by 1,2-addition of methallyl Grignard reagent to bis(alkylthio)methylidene derivative ofdimedone 2a-c wewr converted to the cycloaromatization product 4 assisted by boron trifluoride etherate.When this reaction was performed in methanol,the substitution-cycloaroatization product 5 was obtained as by- product from 3c.To this eycloaromatization reaction,,the reactivity order dimethylthio>1, 3 - propylenedithio>1, 2- ethylenedithio carbon cation was established by the yields from 3a-c 4.An intramolecular a1,a1reaction pattern was developed by experiment.

α-溴代二硫缩烯酮的制备及其反应

Bromo ketene dithioacetals (5) were prepared in high yields by reaction of α,α-diacetyl ketene dithioacetals (4) with bromine catalyzed by FeBr 3 at room temperature. This new reaction is proposed involving an ipso electrophilic addition-deacetylation mechanism.

α-乙酰基二硫缩烯酮的新合成方法

The α-acetyl ketene dithioacetals 2, which bear various alkylthio groups, are a kind of important intermediates in organic synthesis. In this paper, dithioacetals 2 were prepared in very high yields (90%—100%) via the deacetylation reaction of the corresponding α,α-diacetyl ketene dithioacetals 1 in the presence of concentrated sulfuric acid. This reaction involves an %in-situ% electrophilic addition-deacetylation mechanism and shows the nucleophilicity of the α-carbon atom in α-oxo ketenedithioacetals. Meanwhile, when the reaction time was prolonged to 22—25 h, the β-keto thiolesters 3a and 3c were produced in good yields.

α,α-二乙酰基二硫缩烯酮和芳醛的缩合反应研究

在碱性条件下 ,α,α-二乙酰基二硫缩烯酮和芳醛的缩合反应受烷硫基的影响 .α,α-二乙酰基二苄硫缩烯酮 1和芳醛 3缩合生成单面缩合脱乙酰基产物α-肉桂酰基二苄硫缩烯酮 4 ;α,α-二乙酰基环二硫缩烯酮 2和芳醛 3缩合生成双面缩合产物α,α-二肉桂酰基环二硫缩烯酮 5 .

α-溴代-α-乙酰基二硫缩烯酮与芳醛缩合反应的研究

从α-溴代-α-乙酰基二硫缩烯酮出发,与多种不同芳醛反应合成了γ-位的醛缩合产物α-溴代-α-烯酰基二硫缩烯酮.探讨了在不同碱、溶剂、反应温度和原料配比等反应条件下该缩合的反应情况及其产率,并对各化合物的结构进行了表征.结果表明,在以氢氧化钠为碱,叔丁醇为溶剂,常温条件下可以较高产率地获得目标产物.

α-羰基烯酮二硫代缩醛化学研究进展(Ⅳ)

在作者以前工作的基础上，针对α－羰基烯酮二硫代缩醛的缩合反应及其他一些反应进行归纳率总结．研究发现反应物中二硫缩醛基的结构对缩合反应有着深远影响，其中将具多官能团的α－羰基烯酮二硫代缩醛同具生物活性的有机锡酯类化合物结合起来研究是该课题组近期研究的新成果．

α-羰基烯酮式环二硫代缩醛类化合物的制备

从具有α-亚甲基的酮出发,利用溶液稀释的方法,提高了用Dieter法合成α-羰基烯酮式环二硫代缩醛类化合物的产率,并用改进方法合成了4个该类化合物。

α－芳甲酰基烯酮二硫缩醛的新合成方法

以碳酸钾为碱，芳甲酰丙酮（１）与二硫化碳、卤代烃反应得到２－乙酰基－２－芳甲酰基烯酮硫代缩醛（２），２在乙硫醇钾作用下脱乙酰基生成标题化合物（３）。１→３的转化具有反应条件温和、产物产率高及对３中各种缩醛基均可通用等特点。

α,α-二羰(酯)基烯酮二硫代缩醛化合物的碱性分解反应

在乙硫醇钾或醇钠（钾）作用下，α，α－二羰（酯）基烯酮二硫代缩醛（１）可能经由逆Ｃｌａｉｓｅｎ缩合历程生成相应的β，β－双烷硫基丙烯酸酯或α－羰基烯酮二硫代缩醛类化合物（２）。以醇钠（钾）为碱时，２的产率较低．用乙硫醇钾为碱时，２的产率可达６６％以上；本实验为化合物２的合成提供了一条简单、有效的途径．

α-羰基烯酮二硫代缩醛化学研究进展(Ⅰ)

综述了９０年代以来有关α－羰基烯酮二硫代缩醛类化合物的最新进展，限于篇幅，首先对其制备及结构特征做出总结．

α-羰基二硫缩烯酮的研究进展

综述了α-羰基二硫缩烯酮的结构特征、合成方法及作为1,3-亲电体的普通环合反应、环合芳构化和取代-环合芳构化反应、合成杂环化合物、缩合反应、极性翻转合成策略、还原反应等在有机合成中的应用.

α-羰基烯酮环二硫代缩醛化学（Ⅺ）──α-羰基烯酮环二硫代缩醛类化合物与Reformatsky试剂的加成反应初步研究

报道了标题化合物和Ｒｅｆｏｒｍａｔｓｋｙ试剂［Ｅｔｈｙｌ（ｂｒｏｍｏｚｉｎｃｉｏ）ａｃｅｔａｔｅ］的加成反应。实验表明，该加成反应能否进行和α－羰基烯酮二硫代缩醛类化合物中缩醛基结构密切相关．结合晶体结构数据和构象分析可以推测，当缩醛基的两个烷硫基处在（或近于）同一平面上时，因满足了两个硫原子和Ｒｅｆｏｒｍａｔｓｋｙ试剂形成络合物的电子要求，底物被活化而易发生加成反应；反之，两个烷硫基难于处在同一平面上时，加成反应难以进行。

α，α－二乙酰基烯酮二硫代缩酮的碱分解反应及缩酮基的稳定性研究

通过α，α-二乙酰基烯酮二硫代缩酮在乙硫醇钾作用下的分解作用制备了乙酰基烯酮二硫代缩酮．找出了最佳反应条件，探讨了缩酮在反应条件下的稳定性．

MMT/FeCl_3催化的α-羰基二硫缩烯酮与二苯甲醇的Friedel-Crafts烷基化反应

研究了MMT/FeCl_3催化α-羰基二硫缩烯酮与二苯甲醇的Friedel-Crafts烷基化反应,合成了22个二硫缩烯酮类化合物(3a^3v),其中3b,3d^3f,3h^3r和3t为新化合物,其结构经1H NMR和13C NMR表征。以3a的合成为例,对反应条件进行优化。结果表明:在最优反应条件[1-(1,3-二噻烷-2-亚甲基)-4-苯基-3-丁烯-2-酮(1a)0.25 mmol,二苯甲醇0.3 mmol,MMT/FeCl_315 mmol%,CH_2Cl_22 m L,回流反应2 h]下,3a产率93%;MMT/FeCl_3循环使用3次,收率基本维持不变。

α-羰基烯酮环二硫代缩醛类化合物在酚类化合物合成中的应用及其机理探讨──8-羟基及8-甲氧基卡拉烯的合成

在氯化汞和三氟化硼乙醚络合物催化下，从（－）－薄荷酮生成的α－羰基烯酮环二硫代缩醛和甲代烯丙基氯化镁经１．２加成所生成的醇，以甲醇、水分别作为溶剂和亲核试剂可发生重排－环合作用，得到８－甲氧基和８－羟基卡拉烯。其机理涉及碳正离子重排及碳正离子－烯键分子内环合反应。本反应为从酮（或醛）出发合成酚类化合物的一个新途径。