Development of Chiral Ferrocenyl Compounds including Hetero Atoms and Their Use in Asymenetric Synthesis

我们发展了一种用手性二茂铁硒试剂将手性化合物引入有机分子的方法。这些试剂适用于手性化合物如联烯、4-烷基-1-亚烷基环己烷、b-羟烷基硒醚、烯丙醇和烯丙胺的不对称合成。在本报告中，我们提出了新的方法来制备几个具有高立体选择性的杂环。使用光学活性的2-[1-（二甲氨基）乙基]二茂铁硒基阳离子进行烯酸、烯醇和烯基二氢硒的不对称分子内硒环化反应，分别以良好至优异的化学产率（高达97%）和非常高的非对映选择性（高达98%de）顺利地得到相应的含内酯、环醚和N-杂环的有机硒基部分。反阴离子的性质对环化反应的非对映选择性有显著影响，PF_6和BE_4分别对烯酸和烯醇的非对映选择性最好，而对烯基醚的非对映选择性最好。环化反应的合理反应方案，其中手性selenylating剂的方法的碳-碳双键的基板从体积较小的方向，以提供一个手性episelenonium离子，然后由亲核试剂的分子内背面攻击。

We have developed the methodology to introduce chilalities into organic molecules using chiral ferrocenylselenium reagents. These reagents are applicable to asymmetric synthesis of chiral compounds such as allenes, 4-alkyl-1-alkylidenecyclohexanes, b-hydroxyalkyl selenides, allylic alcohols, and allylic amines. In this report we present new methodology to prepare several heterocycles with a high stereoselectivity. Asymmetric intramolecular selenocyclization of alkenoic acids, alkenols, and alkenyl urethanes using optically active 2-[1-(dimethylamino)ethyl]ferrocenylselenenyl cations proceeds smoothly to give the corresponding organoselenenyl moiety containing lactones, cyclic ethers, and N-heterocycles, respectively, in good to excellent chemical yields (up to 97%) with very high diastereoselectivities (up to 98% de). The nature of counter anions of the selenenylating agents affected remarkably the diastereoselectivity of the cyclization, PF_6 and BE_4 being revealed to be the best for that of alkenoic acids and alkenols and that of alkenyl urethanes, respectively. The plausible reaction scheme for cyclization is presented where a chiral selenenylating agent approaches the carbon-carbon double bond of the substrate from the less bulky direction to afford a chiral episelenonium ion followed by an intramolecular back side attack of a nucleophile.