Asymmetric Synthesis of Five-membered Compounds by Transition Metal-Catalyzed Asymmetric Cyclizations of Enyne Systems

烯烃类化合物在钯、镍、钴、铑等过渡金属催化剂作用下发生环化反应。手性辅助剂的使用为不对称合成环状化合物提供了一种新的策略。我们最近对过渡金属不对称环化反应的研究结果如下所示。在钯催化的反应中，使用含有两个具有相同取代基的烯烃部分和乙炔基团的对称底物，通过使用底物或手性配体中涉及的手性亚氨基基或(S)-脯氨酸衍生基团来提供对映体区分反应产物。钯催化的不对称环异构化反应适用于1，6-烯炔体系，体系中含有手性亚硫基、(S)-脯氨酸或(S)-四氢异喹啉衍生基团作为手性助剂或使用手性配体，为手性五元化合物提供了一个新的入口。…简介更多的羧基进入1，6-烯炔底物提供了更高的非对映或对映体选择性，这可能是因为通过羧基与体系中涉及的钯催化剂的配位来立体控制生成的中间体钯配合物的构象。首次利用手性膦配体催化不对称Pauson-Khandd反应，观察到取代基在获得高对映体选择性方面的显著作用。已经尝试引入手性有机硫官能团，例如亚磺基或亚磺酰胺基团。观察到手性有机硫基的效率略低。通过使用(S)-蛋氨酸衍生底物进行Pauson-Khandd反应，也揭示了有机硫官能团的参与。通过与由(S)-蛋氨酸和(S)-S-甲基半胱氨酸衍生的手性底物所涉及的亚硫基在钴催化反应中的作用进行了比较，并与由(S)-去甲伐氨酸和(S)-去甲亮氨酸衍生的无有机硫功能的底物所得到的结果进行了比较。通过X射线晶体分析确定了产物的结构。在立体化学结果的基础上提出了反应机理。测定了钯催化1，3-丁二烯基环戊烯衍生物转化为环戊烯的立体化学。通过与以手性乙烯基亚砜为起始底物的两种几何异构体的立体化学结果的比较，揭示了手性亚硫基参与了钯的催化作用。较少

Enyne compounds undergo cyclization reactions, upon treatment with transition metal catalysts such as palladium, nickel, cobalt, rhodium and so on. The use of chiral auxiliaries involved in the systems or chiral ligands provides a new strategy for asymmetric synthesis of cyclic compounds. Our recent results of asymmetric cyclizations with transition metals along these lines are as follows.1. The use of symmetric substrates involving two olefinic parts with the same substituents and an yne group in palladium-catalyzed reactions provided enantiotopic differentiating reaction products by using chiral sulfinyl or (S)-proline-derived groups involed in the substrates or chiral ligands.2. The palladium-catalyzed asymmetric cycloisomerizations were applicable to 1,6-enyne systems involving chiral sulfinyl, (S)-proline or (S)-tetrahydroisoquinoline-derived groups in the systems as chiral auxiliaries or using chiral ligands, providing a new entry to chiral five-membered compounds. Introduction o … More f a carboxyl group into the 1,6-enyne substrates provided higher diastereo- or enantioselectivity, presumably due to stereocontrol of the conformation of the resultant intermediary palladium complexes by coordination of the carboxyl groups to the palladium catalysts involved in the systems.3. The first catalytic asymmetric Pauson-Khand reaction has been developed by using chiral phosphine ligands, in which dramatic effects of the substituents were observed in achieving high enantioselectivity. Introduction of chiral organosulfur functionality such as sulfinyl or sulfinamide groups has been attempted. Slightly low efficiency was observed with the chiral organosulfur groups. Participation of organosulfur functionality was also revealed by the use of (S)-methionine-derived substrates for the Pauson-Khand reactions. The role of the sulfenyl groups involved in the chiral substrates derived from (S)-methionine and (S)-S-methylcystein in the cobatlt catalysis was reveiled in comparison with the results obtained from the substrates without organosulfur functionality, derived from (S)-norvaline and (S)-norleucine. The structure of the product was determined by the X-ray christallographic analysis. The reaction mechanism is proposed on the basis of the stereochemical results obtained.4. The stereochemistry of the palladium-catalyzed conversion of (1,3-butadienyl) cyclopentene derivatives into cyclopentenes was determined. The participation of the chiral sulfinyl groups in the palladium catalysis was revealed by the comparison with the stereochemical results between two geometrical isomers of the chiral vinylic sulfoxides employed as starting substrates. Less