Development of New Molecular Recognition Chemistry using Organoaluminums

体积特别大、亲氧的甲基铝双(2，6-二叔丁基-4-甲基苯氧基)(MAD)可以作为Lewis酸性受体与一系列羰基化合物、乙醚和环氧化物络合。通过低温核磁共振谱研究发现，MAD与含氧底物的配位顺序为：酰胺类、醛类、酮或酯类、环氧化物和醚类。即使在结构上非常相似的羰基化合物也可以很容易地被MAD分离。这一观察结果使得非对称富马酸盐的高度区域和立体控制的Diels-Alder反应建立在两个不同的富马酸羧基与MAD的区别基础上。MAD的高识别能力被成功地应用于使用MAD类型的聚合有机铝试剂的络合层析来清洁分离结构上非常相似的醚。该聚合物有机铝柱也可用作催化环氧化物重排为羰基化合物的固态反应器。基于MAD的分子识别化学，以光学活性的3，3‘-双(三芳基硅基)联苯酚为原料，合成了一种新型的手性有机铝试剂。这些手性有机铝试剂对烯丙基乙烯基醚的不对称Claisen重排以及双烯和不饱和酯的不对称Diels-Alder反应具有很高的应用价值。

Exceptionally bulky, oxygenophilic methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) can be utilized as a Lewis acidic receptor for complexation with a series of carbonyl compounds, ether, and epoxides. By using low-temperature ^<13>C NMR spectroscopy, MAD was found to coordinate strongly to oxygen-containing substrates in the order of amides, aldehydes, ketones or esters, epoxides, and ethers. Even structurally very similar carbonyl compounds can be easily separated by MAD. This observation enabled the highly regio- and stereocontrolled Diels-Alder reaction of unsymmetrical fumarates based on the discrimination of two different fumarate carbonyls with MAD. The high recognition ability of MAD is successfully applied to the clean separation of structurally very similar ethers by complexation chromatography using MAD-type, polymeric organoaluminum reagents. This polymeric organoaluminum column is also employable as solid-state reactor for catalytic rearrangement of epoxides to carbonyl compounds. Based on the molecular recognition chemistry with MAD, a new type of chiral organoaluminum reagents have been developed which are prepared from trimethylaluminum and optically active 3,3'-bis(triarylsilyl)binaphthols. These chiral organoaluminum reagents are highly useful for asymmetric Claisen rearrangement of allylic vinyl ethers and asymmetric Diels-Alder reaction of dienes and unsaturated esters.