Preparation of Chiral ferrocenyl Chalcogenides and their Application to asymmetric Synthesis

合成了一系列手性芳基硒基为手性助剂的α-硒甲基酮，并对其进行了不对称还原、烷基化和氧化重排等立体化学研究。以手性二茂铁胺、恶唑啉和烷氧苯为手性芳基。用二异丁基氢化铝（DIBAH）还原手性二茂铁硒甲基酮得到的产物几乎是单一的，而苯基衍生物的选择性很低（27%）。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选择性（高达36% de），得到β-羟基硒化物，而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草酸锡处理后分别转化为醇和环氧化物。将硒基丙烯酮转化为α-硒基缩醛，并与间氯过苯甲酸（m-CPBA）进行氧化苯基重排。关键中间体α-硒缩醛的几种方法都失败了。对α-烷氧基硒化物发生氧化重排反应的可能性进行了考察。用过量5倍的m-CPBA在甲醇中处理重组产物3-苯丙醇，但收率较低（7%）。原苯基与α-硒缩醛的氧化迁移在高产率下进行，反应的驱动力应该是缩醛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正离子，认为重排反应产物的产率较低。

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.