Preparation of Chiral ferrocenyl Chalcogenides and their Application to asymmetric Synthesis

合成了一系列含手性芳基硒基的α-硒甲基酮手性助剂，并对其不对称还原、烷基化、氧化重排等反应进行了立体化学研究。手性二茂铁胺、恶唑啉和烷氧基苯用作手性芳基。手性二茂铁硒甲基酮与二异丁基氢化铝（DIBAH）还原得到几乎单一的产品，而与苯基衍生物导致低选择性（27% de）。二茂铁硒甲基酮与有机金属试剂如格氏试剂和有机锡化合物的烷基化反应具有中等的选择性（高达36%de），得到β-羟基硒醚，苯基衍生物的选择性较差（5%de）。α-羟基硒化合物经氢化锡和氧硼酸化分别转化为醇和环氧化物。以间氯过苯甲酸（m-CPBA）为催化剂，将硒代苯丙酮转化为α-硒代缩醛，并进行了氧化苯基重排反应。合成关键中间体α-硒代缩醛的几种方法都失败了。对α-烷氧基硒醚氧化重排反应的可能性进行了考察。观察到重排产物3-苯基丙醛用5倍过量的m-CPBA在甲醇中处理，但产率低（7%）。α-硒代缩醛的初始氧化苯基迁移反应以较高的产率进行，反应的驱动力应该是缩醛基团稳定的碳正离子中间体。在该反应中，单个甲氧基不能充分稳定碳阳离子，并且认为重排反应产物的产率低。

A series of α-selenomethyl ketones having chiral arylseleno groups as chiral auxiliaries were synthesized, and the stereochemical research was carried concerning to asymmetric reduction, alkylation, and oxidative rearrangement. The chiral ferrocenyl amine, oxazoline and alkoxy benzene was used as a chiral aryl group. Reduction of chiral ferrocenylselenomethyl ketones with diisobutylaluminum hydride (DIBAH) gave the almost single product, while with the phenyl derivative resulted in low selectivity (27% de). The alkylation of ferrocenylselenomethyl ketone with organometallic reagents such as Grignard reagents and organotin compounds proceeded with moderate selectivities (up to 36% de) to give the β-hydroxy selenides, with the phenyl derivative resulted in poor selectivities (5% de). Theα-hydroxy selenium compound was converted to the alcohol and the epoxide being treated tin hydride and oxaborate, respectively. The seleno propiophenone was converted intoα-seleno acetal, in which was attempted oxidative phenyl rearrangement by m-chloroperbenzoic acid (m-CPBA). Several approach to key intermediateα-seleno acetal have been failed. The examination was carried out on the possibility of the oxidative rearrangement reaction of theα-alkoxy selenide. The rearranged product, 3-phenylpropanal was observed treating it with five time excess m-CPBA in methanol but in low yield (7%). The original oxidative phenyl migration with α-seleno acetal, proceeds in the high yield, and the driving force of the reaction should be the stabilized carbocation intermediate by acetal group. A single methoxy group can not sufficiently stabilize the carbocation in this reaction and that it considers that the yield of the rearrangement reaction product is low.