Synthesis of Cage-Shaped Aluminum Aryloxides: Efficient Lewis Acid Catalyst for Stereoselective Glycosylation Driven by Flexible Shift of Four- to Five-Coordination.

Monomeric cage-shaped aluminum aryl oxides Al were synthesized using tripodal triphenolic ligands. The Lewis acidity and catalytic activity of the obtained Al·py were investigated. The Lewis acidity of Al·py originates from the flexible change in the coordination number of the aluminum center, allowing the catalytic -glycosylation to occur with a high efficiency and an unusual stereoselectivity.

C -Symmetric Boron Lewis Acid with a Cage-Shape for Chiral Molecular Recognition and Asymmetric Catalysis.

Chiral Lewis acids play an important role in the precise construction of various types of chiral molecules. Here, a cage-shaped borate 2 was designed and synthesized as a chiral Lewis acid that possesses a unique C -symmetric structure composed of three homochiral binaphthyl moieties. The highly symmetrical structure of 2 with homochirality was clearly elucidated by X-ray crystallographic analysis.