Development of New Molecular Recognition Chemistry using Organoaluminums

体积庞大的亲氧甲基铝双（2,6-二叔丁基-4-甲基苯氧化合物）（MAD）可作为刘易斯酸受体与一系列羰基化合物、醚和环氧化物络合。通过低温^<13>C核磁共振波谱，发现MAD与含氧底物的配位性强，其顺序为酰胺、醛、酮或酯、环氧化物和醚。即使结构非常相似的羰基化合物也可以很容易地用MAD分离。这一发现使得不对称富马酸盐的diols - alder反应具有高度的区域和立体控制，该反应基于MAD对两种不同的富马酸羰基的识别。MAD的高识别能力成功地应用于用MAD型聚合有机铝试剂络合色谱法对结构非常相似的醚进行干净分离。这种聚合有机铝柱也可用作固态反应器，用于催化环氧化合物重排为羰基化合物。基于分子识别化学，以三甲基铝和旋光性3,3′-双（三芳基硅基）联萘酚为原料，研制了一种新型手性有机铝试剂。这些手性有机铝试剂在烯丙基乙烯醚的不对称Claisen重排和二烯与不饱和酯的不对称Diels-Alder反应中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.