Radical cyclization of sulfonyl derivatives and N-aziridinylimine

Abstract

Sulfonyl radicals are generally recognized as useful intermediates in the synthesis of organosulfones. A phenylsulfonyl induced addition-cyclization reaction followed by carbon-carbon bond formation with sulfonyl derivatives gave a,b-functionalized cyclopentanes under tin-free conditions. Toluenesulfonyl cyanide, 2-phenylsulfonyl and 2-ethoxycarbonyl allyl sulfone , were used as radical acceptors. Radical cyclization of diethylmalonate (1) with sulfonyl derivatives give cyclopentanes in 50-72% yield. Similar results were obtained with diallylbenzenesulfonamide (2) and diallyl ether (17). Except phenyl sulfonyl bromide, phenylsulfonyl radical induced addition-cyclization reaction of enynes and diynes was not successful, yielding very low yields of the products. Similarly, bis(allens) and monoallens were unsuccessful. The relative reactivity of 2-phenyl-N-aziridinylimino group relative to alkenyl and alkynyl groups using stannyl, silyl, and phenyl sulfonyl radical was investigate to study the possibility of N-aziridinylimines as radical precursors. The competition between an alkenyl and N-aziridinyl group showed the preference of the alkenyl group over the imino group as a radical acceptor. Also, the competitions between an alkynyl and N-aziridinyl group indicated the preference of the alkynyl group over the imono group.