Highly Selective Synthetic Transformations Catalyzed by Lithium Perchlorate in Organic Media

Highly concentrated solutions of lithium perchlorate in various organic solvents have been used as media for many synthetic transformations at room temperature which are otherwise difficult to carry out under ordinary conditions. The rates of several organic reactions are faster in these media compared than in pure solvents. More importantly high chemo-, regio- and stereoselectivities have been observed. The mild Lewis acidity of the lithium ion in donor solvents such as diethyl ether is responsible for these selectivities. Fine tuning of the Lewis acidity of the lithium ion, depending upon the solvent basicity and polarity, has been possible for selective activation of organic substrates in these media. The activation of carbonyl- and other oxygen-containing organic compounds in 5 M lithium perchlorate in diethyl ether (LPDE) and in nitromethane (LPNM) is presented.