Preparation of Chiral ferrocenyl Chalcogenides and their Application to asymmetric Synthesis

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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.