Chemo- and Regioselective Conversion of Epoxides to Carbonyl Compounds in 5 M Lithium Perchlorate-Diethyl Ether Medium.

Abstract

Epoxides are useful substrates in organic synthesis due to their high reactivity.1 Conversion of an epoxide to a carbonyl compound is a synthetically useful reaction, and BF3 and its etherate are the most commonly used reagents for this purpose.2 Unless there is a structural or a stereochemical bias, generally multiple products are obtained due to the lack of regioselectivity in the ring opening step. Moreover, lack of chemoselectivity among various substituted epoxides limits the synthetic utility of this reaction in multistep synthesis. In fact, no epoxide has been reported to be insensitive to BF3. Lithium and magnesium halides have been used for epoxide ring opening reaction.2-4 Recently, chemo and regioselective isomerization of epoxides to carbonyl compounds by a palladium catalyst has been reported.5 Lithium perchlorate in refluxing benzene has been reported to be a very useful reagent for the rearrangement of several epoxides as it shows higher product selectivity compared to strong Lewis acids.2,3,6 Recently, 5 M lithium perchlorate in diethyl ether (LPDE) has been shown to be an excellent medium for several synthetic transformations, and high chemo-, regio-, and stereoselectivities have been reported.7 In our efforts to use this medium for selective synthetic transformations,8,9 we have investigated the ring opening reaction of epoxides, and herein we report our results.