A mini-review on air-stable organometallic Lewis acids: Synthesis, characterization, and catalytic application in organic synthesis

Organometallic Lewis acids play an important role in modern organic synthesis. How to design and synthesize highly efficient and recyclable organometallic Lewis acid catalysts that can be conveniently applied in chemical reactions are key issues for sustainable synthetic processes. In general, stronger acidity means higher catalytic activity for organometallic Lewis acids. However, with the rise in acidity, the compound becomes more susceptible to hydrolysis and cannot be recycled. Simultaneous improvement of the hygroscopic character and Lewis acidity/catalytic activity of organometallic Lewis acids is highly desirable from the standpoint of practical applications. In this mini-review, the history of air-stable organometallic Lewis acids is introduced, with emphasis on our research works on metallocene, organobismuth, and organoantimony Lewis acids to the aspects of synthesis, characterization and catalytic application in carbon-carbon bond (Friedel-Crafts acylation, Mukaiyama aldol reactions; allylation, cyclotrimerization, Mannich reactions, cross-condensation reactions) and carbon-heteroatom bond (acylation, S-S bond cleavage, glycosylation) formation reactions. In terms of stability, storage, versatile ability, high catalytic activity and chemo-/stereo-selectivity, the complexes will find broad applications in organic synthesis.