On the scope of diastereoselective epoxidation of various chiral auxiliaries derived enones: the conformational analysis of camphor derived N- and O-enones

Various camphor derived N- and O-enones were treated with selected oxidants to provide the corresponding epoxides in a wide range of diastereoselectivity. For camphorsultam derived activated alkenes, high to excellent stereoselectivities were obtained when the s-trans enones were treated with methyl(trifluoromethyl)dioxirane. On the other hand, for exo-10,10-diphenyl-2,10-camphanediol (3) and exo-10,10-diphenyl-10-methoxy-2-camphanol (4) derived alkenes, the use of s-cis enones gave the desired epoxide with excellent diastereoselectivity under the same reaction conditions. The stereoselectivity was highly dependent on the geometry of the auxiliaries derived enones and the stereochemical induction is discussed.     

5-羟基色胺受体激动剂(1R,2S)-(-)-2-(2-羟基苯基)-N,N-二丙基环丙胺的不对称合成

利用手性双唑啉与三氟甲磺酸亚铜催化2-甲氧基苯乙烯与重氮乙酸二环己基甲酯的不对称环丙烷化反应合成了手性环丙烷羧酸酯,用氢氧化钠对其进行选择性水解得到全反式环丙烷羧酸,其ee值经GC测定为88%.进一步经过Curtius重排、烷基化等反应及重结晶等步骤合成了光学纯的具有生理活性的环丙胺化合物1a和1b.     

新型手性磷化合物的合成及其作为配体催化剂在某些不对称合成反应中的应用

从L-氨基酸、D-樟脑、(-)-假麻黄碱、(-)-α-苯乙胺、(S)-(-)-联萘二酚等旋光源出发,合成了26个三配位及四配位手性磷化合物.作为配体催化剂,试验了它们在潜手性酮及亚胺的不对称硼烷还原反应、醛与二乙基锌的不对称烷基化反应以及醛的不对称硅腈化反应中的催化活性.发现其中有些催化剂有很好的立体选择性.     

Enantioselective syntheses of (E)-γ,δ-disubstituted homoallylic alcohols via BF3·OEt2-catalyzed aldehyde allylboration and analysis of the origin of E-selectivity: A1,2 allylic strain vs. syn-pentane interaction

Enantioselective allylboration of aldehydes with α-substituted β-methyl allylboronate was reported. By using BF₃·OEt₂ as the catalyst, γ,δ-disubstituted homoallylic alcohols were obtained in good yields with high E-selectivities and enantioselectivities. Transition state analysis revealed that the disfavored transition state suffers from a syn-pentane interaction between the BF₃ catalyst and axially oriented α-substituent of the allylboron reagent. Such a syn-pentane interaction is severe enough to overcome the A^1,2 allylic strain between the β-methyl group and the α-substituent of the boron reagent that is present in the favored competing transition state. Consequently, the reaction proceeded with equatorial placement of the α-substituent to furnish γ-methyl substituted homoallylic alcohols with high E-selectivity.     

不对称Reformatsky反应

综述了６０年代至今不对称诱导和不对称催化Ｒｅｆｏｒｍａｔｓｋｙ拔应的研究，进展参考文献１９篇。     

Enantioselective synthesis induced by chiral organic-inorganic hybrid silsesquioxane in conjunction with asymmetric autocatalysis

5-Pyrimidyl alkanol with up to 96% ee was formed using chiral organic-inorganic hybrid silsesquioxane in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde, in conjunction with asymmetric autocatalysis.     

新型手性膦-硼烷配合物的合成及其在不对称催化氢化反应中的应用

以苯乙烯为原料,通过Sharpless不对称二羟基化反应合成高对映体纯的苯基乙二醇,经酯化、亲核取代反应转化为手性膦-硼烷配合物.后者克服了有机膦配体易氧化的缺点,其制备过程简单,易于提纯,在空气中可长期保存.该手性膦-硼烷配合物在四氟硼酸-甲醚的存在下解络,生成的自由膦不经分离直接与[Rh(COD)Cl]₂作用生成手性膦-铑原位催化剂.在α-乙酰氨基肉桂酸甲酯的不对称氢化反应中,转化率为100%,对映选择性88%e.e.     

Chiral imidates as a new class of nitrogen-based chiral ligands: synthesis and catalytic activity in asymmetric aziridinations and diethylzinc additions

Chiral imidates were efficiently synthesized in one step and with high yields (seven examples). These chiral imidates were used as ligands in the Cu(I)-catalyzed asymmetric aziridination of methyl cinnamate and in the asymmetric diethylzinc additions to benzaldehyde as a proof of principle. The imidate catalyst system showed high catalytic activities and induced encouraging selectivities. An X-ray structure analysis of an imidate-Cu(I) complex is included, showing a distorted tetrahedral arrangement with two bidentate ligand molecules surrounding the metal.     

2-Pyridylsulfinamides as effective catalysts in the asymmetric alkylation of aldehydes with diethylzinc

Chiral 2-pyridylsulfinamides were shown to be effective catalysts in the alkylation of aryl and alkyl aldehydes with diethylzinc providing the corresponding alcohols in excellent enantioselectivity. Sulfinamide catalysts possessing solitary chirality at the sulfur center produced the product phenethyl alcohol in good enantioselectivity. Diastereomeric sulfinamides possessing chirality at the carbon-bearing nitrogen and at the sulfur of the sulfinamide increased the enantioselectivity of the product alcohols up to >99%. However, there is no effect of the match-mismatch pair of sulfinamide diastereomers on the outcome of the chiral induction of the product phenethyl alcohols. It was conclusively proved that chirality at the sulfur center is mandatory for obtaining good enantioselectivity in the reaction.     

Stereoselective synthesis of hyptolide and 6-epi-hyptolide

The first stereoselective syntheses of the naturally occurring, ,β-unsaturated lactone hyptolide 1 and of its nonnatural epimer at C-6 are described. Ethyl l-lactate was the chiral starting material. Key steps of these syntheses were a Brown's asymmetric allylation, a Carreira's asymmetric ethynylation and a ring closing metathesis.