不饱和Grignard试剂与不饱和酯的共轭加成 Ⅴ.亚烃基丙二酸亚异丙酯与乙烯型烯基溴化镁的加成

在I,II和IV报中,曾报道了乙烯型烯基溴化镁分别与亚烃基丙二酸二乙酯、亚烃基乙酰乙酸乙酯及乙烯四羧酸四乙酯的共轭加成反应.本文报道乙烯型烯基溴化镁与亚烃基丙二酸亚异丙酯(1)的加成反应.1由丙二酸亚异丙酯(2)与醛或酮进行Knoevenagel反应制得.2又称为Meldrum’s acid,即2,2-二甲基-1,3-二氧杂环己二酮-[4,6],是一种酸性较强(pK_a=4.83),易于制备,具有稳定环状结构的酯.由于其亚甲基很活泼,具有多种反应性能,因此,近年来在有机合成上引起人们较大的兴趣. 以过量乙烯型烯基溴化镁,在催化量无水CuCl存在下陷,与1进行共轭加成反应,可制得一系列新化合物——β,γ-不饱和仲烃基(或叔烃基)丙二酸亚异丙酯(3).反应式如下:     

不饱和格氏试剂与不饱和酯的共轭加成 Ⅳ.乙烯四羧酸四乙酯与烯烃基溴化镁的加成作用

邢其毅等^[1]研究了烷基、芳基格氏试剂对乙烯四羧酸四乙酯的加成,发现这类反应为1,4-加成^[2~6].     

月桂烯环加成合成不饱和的环状硫醚

由二苯甲酮合成二苯甲硫酮，再使它与月佳烯发生环加成反应，合成了两种不饱和环状硫醚，总产率７４．６％。     

亚甲基丙二酸亚异丙酯衍生物的氰化加成

对5-位不饱和双键的氰化加成进行了研究,合成了一系列新的5-氰基甲基丙二酸亚异丙酯的衍生物.     

丙二酸亚异丙酯的双Michael加成

丙二酸亚异丙酯(Isoproplidene malonate orMeidrum's acid)是一种有用的有机合成中间体。最近,陈振初等报道了丙二酸亚异丙酯和某些亲电烯烃(CH_2=CHCO_2Et,CH_2=CHCN,CH_2=CHCOCH_3,EtO_2CCH=CHCO_2Et)     

不饱和酮亚胺叶立德的分子内共轭加成

对不饱和酮亚胺叶立德的分子内共轭加成进行了考察.以67%~99%的产率以及20∶1的非对映选择性得到相应的高度官能团化的3,4-二氢-2H-吡咯衍生物.     

亚烷基卡宾与甲醛环加成反应机理的理论研究

用二阶微扰理论研究了单重态亚烷基卡宾与甲醛发生的三种环加成反应的机理 ，采用MP2/6－31G~*方法计算了势能面上各驻点的构型参数、振动频率和能量。根 据能量数据可以预言环加成反应（1）的a途径将是单重态亚烷基卡宾与甲醛环加成 反应的主要反应通道，该反应由两步组成：（I）亚烷基卡宾与甲醛生成了一富能 中间体（INT1a），是一无势垒的放热反应，（II）中间体异构化为产物亚烷基环 乙烷，其势垒为24.1 kJ·mol~(-1)(MP2/6-31G~*)。     

端炔与对亚甲基苯醌的1,6-加成

为了合成selaginellin家族天然产物,我们开发了炔锂和对亚甲基苯醌的1,6-加成反应。研究了此反应的反应条件及底物适用范围和限制。结果表明,对亚甲基苯醌苯环上的取代基对反应速率和产率有显著的影响:吸电子基团增加其亲电性,使反应变快,并且可以得到较高的产率;与此相反,给电子基团则降低了对亚甲基苯醌的亲电性,反应变慢,并且表现出可逆性,产率变低。端炔对反应影响很小,均能得到高产率的产物。本方法可用于快速构建selaginellin家族天然产物的骨架结构。     

亚烷基卡宾与丙烯环加成反应机理的理论研究

用二阶微扰理论研究了单重态亚烷基卡宾与丙烯环加成反应的机理，采用 MP2/6-31G~*方法计算了势能面上各驻点的构型参数、振动频率和能量。根据所得 势能面上的能量数据可以预言，反应（1）的a途径和反应（2）的b途径将是单重态 亚烷基卡宾与丙烯环加成反应的两条相互竞争的主反应通道，两反应途径均由两步 组成，(I)两反应物分别生成了富能中间体INT1a和INT2b，它们均是无势垒的放热 反应，放出的能量分别为60.28和26.33kJ·mol~(-1).(II)中间体INT1a和INT2b分 别通过过渡态TS1a和TS2b异构化为三元环产物P1和四元环产物P2，其势垒分别为 16.43和12.73kJ·mol~(-1)。     

Nickel-catalyzed intramolecular addition of vinyl or aryl bromides to ketoamides

A nickel-catalyzed intramolecular addition of vinyl or aryl bromides to ketoamides has been developed. The reactions proceeded efficiently with Ni(bpy)Br₂ as a catalyst and zinc powder as reducing agent, affording 3-hydroxypyrrolidinones, 3-hydroxyoxindoles, and dihydroquinolinones as important heterocyclic compounds in good to excellent yields.     

Conjugate addition of sodium methanesulfinate to vinyl pyridines and diazines for the synthesis of aliphatic sulfones

A convenient method to introduce a sulfone group to pyridines and diazines is described. This efficient method involves the conjugate addition of sodium methanesulfinate to vinyl heterocycles. This process tolerates a wide variety of functional groups and is performed in the presence of acetic or trifluoroacetic acid. A one-pot, two-step synthesis of sulfones starting from the corresponding heteroaryl halide is also described.     

Tetrabutylammonium fluoride-induced dehydrobromination of vinyl bromides to terminal acetylenes

Tetrabutylammonium fluoride (TBAF) was found to be a mild and efficient base for the dehydrobromination of vinyl bromides. Treatment of various 2-bromo-1-alkenes with TBAF·3H₂O in DMF yielded terminal acetylenes in high yields without undue regard to the presence of water.     

Conjugate addition of aromatic amines to ethenetricarboxylates

The conjugate addition of amines is considered to be a useful reaction in synthetic organic chemistry. The reaction of reactive electrophilic olefins, ethenetricarboxylates, and aromatic amines with and without catalytic Lewis acids such as ZnCl₂ and ZnBr₂ at room temperature gave amine adducts in high yields. The products were converted to α-amino acid, dl-aspartic acid derivatives. Using Lewis acids such as Sc(OTf)₃ and Zn(OTf)₂ at higher temperature (40-80 °C), the reaction of ethenetricarboxylates and N-methylaniline gave an aromatic substitution product. A catalytic enantioselective conjugate addition using a chiral Lewis acid was also investigated. For example, the reaction of 1,1-diethyl 2-tert-butyl ethenetricarboxylate with N-methylaniline in the presence of chiral bisoxazoline-Cu(II) complex in THF at −20 °C for 17 h gave an amine adduct in 91% yield and 78% ee. On the other hand, the reaction with aniline and primary aniline derivatives gave adducts with almost no ee%.     

Radical addition to vinyl sulphones and vinyl phosphonium salts

Alkyl radicals, derived from decarboxylation of carboxylic acids, add readily to phenyl vinyl sulphone and vinyl phosphonium bromide. The adducts may be further converted into a variety of useful synthetic intermediates.     

Conjugate addition of organolithium reagents to acrylanilide anions

Phenyllithium, $\text{n}$-butyllithium, and $\text{t}$-butyllithium were found to add to substituted acrylanilide anions to give the 1,4-addition products in fair to good yields.     

Radical addition of methyldichlorosilane to vinyl acetate

The GC-MS method was used to identify the addition products of methyldichlorosilane to vinyl acetate. Radiation-induced addition of methyldichlorosilane to vinyl acetate produces 2-methyldichlorosilylethyl ethyl ether. The reaction follows a radical-chain mechanism. The ratio of the rate constants of methyldichlorosilyl radical addition to C=C and C=O to vinyl acetate amounts to 0.4±0.1 (303 K).

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- . , - 2- . , C=C C=O 0,4±0,1.