SYNTHESIS OF OXIRANES FROM AQUEOUS SOLUTIONS OF SIMPLE ALKYL, ALLYL, AND BENZYLSULFONIUM SALTS

The reaction of simple sulfonium salts with warm aqueous NaOH and carbonyl compounds yields various oxiranes (epoxides). Previously, oxirane syntheses from such sulfonium salts has been achieved only in nonaqueous solutions of much stronger bases. The present work shows that often sufficient sulfonium ylide is formed in aqueous bases to permit trapping reactions. Trimethyl- or triethylsulfonium chlorides gave oxiranes with benzaldehyde (ca. 70%). No oxiranes were formed with formaldehyde nor acetaldehyde, since Cannizzaro or aldol condensation reactions apparently intervened. Allyldimethylsulfonium chloride reacted well with benzaldehyde (ca. 70% oxirane), poorly with formaldehyde (8%), and not at all with acetaldehyde. A side reaction, leading to propylene oxide, also occurred. Benzyldimethylfonium chloride gave oxiranes with both benzaldehyde and formaldehyde (85 and 87%) and, under conditions of minimal exposure to NaOH, with acetaldehyde also (48%). © 1969, American Chemical Society. All rights reserved.