Radical [n+1] annulations with sulfur dioxide and new methodology for the synthesis of specialized N-alkoxyamines.

摘要

A novel methodology for [n+1] radical annulation using sulfur dioxide as a geminal radical acceptor/donor is described. The exo vs. endo selectivity can be tuned by designing either a linear or branched allylic sulfide terminating group into the starting material. This methodology provides a novel route to the formation of 5, 6, and 7-membered cyclic sulfones utilizing a radical chain mechanism under very mild conditions.; A new methodology for the synthesis of the N-alkoxyamines is described. N-Alkoxyamines are useful as initiators in nitroxide mediated "living" free radical polymerization. This procedure utilizes silyl radical abstraction from alkyl halide precursors to prepare N-alkoxyamines inaccessible by other methods. As a demonstration of the utility of this methodology, an initiator for nitroxide mediated "living" free radical polymerization was prepared with a fluorescent tag attached to the initiating alkyl radical terminus. This labeled initiator was used to synthesize amphiphilic poly(acrylic acid)-b-polystyrene diblock copolymers, which self-assembled in a THF/buffer solution to form structures that were visible by fluorescence.