Lithium Perchlorate/Diethyl Ether (LPDE)

Introduction

Lithium perchlorate in diethyl ether has become a widely used medium in organic synthesis in recent years for effecting various organic transformations. [1] The special property inherent to LPDE medium is that it offers a convenient procedure to carry out reactions under essentially neutral reaction and workup conditions. It promotes organic reactions such as aldol condensation, cycloaddition, and sigmatropic rearrangements. Among the many organic reactions mediated by LPDE, one-pot three component aminoalkylation of aldehydes, [2] Mannich reaction, [3] Biginelli reaction [4] are worth to notice. The three component condensation reaction of aldehydes and amines with various nucleophiles also takes place in this medium and leads to the facile synthesis of α-aminonitriles, [5] α-aminophosphonates, [6] α-cyanohydroxylamines, [7] N-trimethysilyloxy-α-aminophosphonates, [8] and α-hydrazinophosphonates. [9] It is expected that more applications will be found with this remarkable reagent and investigations in this medium will be rewarding.

Preparation of LPDE: Commercially available lithium perchlorate [10] was dried under vacuum (10^-1 Torr) at 160 °C for 48 h. Lithium perchlorate is stable up to or above its mp of 247 °C. Anhydrous LiClO₄ and diethyl ether were cooled separately in an ice bath under a nitrogen atmosphere, and then the ice cold ether was added very slowly to LiClO₄ via syringe. The dissolution was highly exothermic. The clear solution can be stored in a desiccator and used as required.

References

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