STUDIES DEALING WITH THE ALKYLATION [1,3]-REARRANGEMENT REACTION OF SOME PHENYLTHIO-SUBSTITUTED ALLYLIC SULFONES

A series of 2-(phenylthio)-3-(phenylsulfonyl)alkenes are easily metalated with n-butyllithium, and the resulting carbanion is regioselectively alkylated by alkyl halides in the a-position to give β,δ-unsaturated sulfones in high yield. These substituted phenylthio allyl sulfones undergo a 1,3-sigmatropic phenylsulfonyl shift by thermal, light-induced, and in some cases acid-catalyzed pathways. Rearrangement occurs where the product sulfone is thermodynamically more stable than the starting material. Cross-over experiments and inhibition studies suggest that the thermal/photochemical reaction occurs by a radical chain mechanism involving a phenylsulfonyl radical. Alkylation of the rearranged sulfones could also be performed under mild conditions. A sequential 1,3-rearrangement-cyclization reaction of 3-alkenyl-substituted allylic sulfones was also studied. The cyclization reaction gives either five- or six-membered ring methyl ketones and was accomplished by using sodium phenylsulfinate in 60% aqueous acetic acid. The cyclization step can be considered as being closely analogous to an intramolecular metallo-ene reaction involving a phenylsulfonyl shift. © 1990, American Chemical Society. All rights reserved.