Microwave-assisted cleavage of aryl methyl ethers with lithium thioethoxide (LiSEt)

摘要

Lithium thioethoxide (LiSEt), a white solid easily prepared from EtSH and n-BULi in hexane, was identified as a highly efficient reagent for the cleavage (O-demethylation) of aryl methyl ethers, i.e. methyl-protected phenols. Of particular synthetic value are applications in the double deprotection of 1,2-dimethoxyarenes (to give catechols) and in the selective monodeprotection of di- and trimethoxyarenes. The thermal reactions, which are usually performed in DNIF as a solvent, can be greatly accelerated through microwave irradiation. In this case, the monodemethylated products are usually formed in high (80-99%) yield within only 15 minutes.