共查询到15条相似文献,搜索用时 78 毫秒
1.
苯甲酰基五氟丙酰基亚甲基三苯基胂的亚甲基上带有两个强吸电子基团.由甲醇-水溶液中获得的该化合物单晶属三斜晶系,空间群为PI;晶胞参数a=12.292A,b=13.457A,c=15.318A,α=90.562°,β=90.516°,γ=92.82°;Ζ=4.用四圆衍射仪收集X射线衍射强度数据,用重原子法进行结构测定,用块对角矩阵阻尼最小二乘法进行结构修正.对8393个独立的可观测衍射点,最后的R因子为0.061.叶立德碳原子具有sp~2杂化的平面构型.As-C(1)键长为1.888A,比As=C双键长得多,也比已报道的其它胂叶立德的相应键长为长,表明“ylene”型结构的贡献较小.强吸电子基团的存在有利于负电荷的离域化,导致化学稳定性的增加. 相似文献
2.
五氟丙酰基甲氧羰基亚甲基三苯基胂是无色透明晶体,属单斜晶系,空间群C_2~2-P2_1.晶胞参数:α=11.917(3)A,b=9.495(1)A,c=11.729(3)A,β=117.82(2)°,Z=2.用四圆衍射仪收集衍射强度数据,得到独立可观察点2558个.用重原子法确定晶体结构,并用块对角矩阵最小二乘法修正结构参数,最后的偏离因子R=0.042.该分子的结构表明,片段As,C(19),C(20),C(23),O(1),O(3)是共平面的. 由于C(19)—C(20)键长较短(1.39A),C(19)—C(23)键长较长(1.45A),因此可以认为叶立德碳上的负电荷主要是向五氟丙酰基上的羰基离域,它的形式为1.此结构信息,符合红外光谱给出的结构,说明该化合物是一稳定的叶立德. 相似文献
3.
The stereochemistry of carbonyl olefination reaction of cyanomethylene triphenylarsorane with ketones is reported. The thermodynamically stable E isomer of the products α, β unsaturated nitrile was formed predominantly. Under the experimental conditions we adopted, the reaction conditions had little effect on the E, Z ratio of the reaction products. However, the structure of the substrate showed profound effect. The results shown in Table 1 are similar to that of the reaction of carbomethoxymethylene triphenylarosorane reported in the previous paper. When methyl t-butyl ketone was used as the substrate and the reaction carried out in benzene solution, nearly pure E isomer was obtained. The reaction mechanism was proposed as shown in the previous paper. When Δ4-cholesten-3-one was used as the substrate, change of the solvents showed more prominent effect on the E, Z ratio of the reaction product. This paper also deals with the reaction of three electron-withdrawing group (CN, COOCH3, COCH3) substituted methyltriphenylarsonium salts with ketones in the presence of K2CO3, Na2CO3/benzo-15-crown-5, K2CO3/18-crown-6 or (C2H5)3N in CH3OH solution. The latter three gave satisfactory results (Table 2). The chromotographically pure products could be obtained from the crude products by passing through silica gel column. Its E, Z ratio is nearly the same as that of the crude product. This method seems to be a good one for preparing olefinic compounds in miligram scale. 相似文献
4.
5.
6.
五氟丙酰基苯甲酰基亚甲基三苯基膦的亚甲基上带有两个强的吸电子基团,属单斜晶系,空间群C2/C,晶胞参数α=11.271(3),b=18.253(6),c=23.938(7)A;β=91.09(2)°;Z=8.用四圆衍射仪收集X射线衍射强度数据,用直接法解晶体结构,用块对角矩阵最小二乘法进行结构修正,参与修正的可观测独立反射点共3146个.最终R=0.075.本文对该膦叶立德的结构进行了测定和讨论,并与已报道的相应的胂叶立德进行比较.叶立德碳原子C(1)与相应的胂叶立德相同,以sp~2杂化轨函参与σ键.P—C(1)键长1.748(5)A,键级1.60;而相应的胂叶立德中As—C(1)的键级1.46,表明前者的“ylene”型结构的贡献比后者大,导致前者的化学活性小于后者.在各种“ylide”型结构中,两者均以负电荷离域化的结构3贡献较大. 相似文献
7.
8.
9.
10.
11.
12.
含氟烯醚可作为亲偶极体进行偶极环加成反应. 某些含氟烯醚在亲核试剂作用下可作为烷基化试剂. 本文报导了Wittig反应通过芳氧. 相似文献
13.
14.
The intramolecular Wittig Reaction has been applied to the synthesis of sec-butyl perfluorobutynoate. the saponification of the product with aqueous sodium hudroxide gave 3-sec-butoxy-4, 4, 4-trifluoro-(2) butenoic acid and 4, 4, 4-trifluoro-3-oxobutyric acid in 1:5 ration. 相似文献
15.
氰基亚甲基三苯基胂(1)与2-全氟炔酸甲酯(2)反应,生成加合产物2-三苯胂基-3-全氟烷基-4-氰基丁烯-3-酸甲酯(3)通过3的水解,立体选择性地合成了3-全氟烷基-4-氰基-3-丁烯酸甲酸甲酯[5(Z),6(E)],Z:E约为95:5.氰基亚甲基三苯基膦(7)与2亦可反应,生成加合产物2-三苯基膦叉-3-全氟烷基-4-氰基丁烯-3-酸甲酯的顺式和反式异构体(8)和(9).总产率在90%左右.8与9的比例受反应介质极性的影响,若溶剂极性增大,则有利于8的生成. 相似文献