Radical relay halogenation

Sodium in liquid ammonia has been recommended for the formation of ethylenic bonds from v/c-dihalides Double bonds have also been introduced at remote positions via radical relay halogenation v/c-Addition of 2 different functions to ethylenic bonds can be adiieved with 2-chlorocarbonyl-l,3-dithiane through a cyclobutanone ring closure and reopening s . 

Kuldtki, V., Ungur, N., Gavagnin, M., Castelluccio, F., and Cimino, G. (2007) Ring B functionalization of scalarane sesterterpenes by radical relay halogenation. Tetrahedron, 63, 7617-7623. 

In this work a reagent, an aryl iodide dichloride, was directly attached to the substrate through a tether, but it had disadvantages. With such a scheme only stoichiometric amounts of the reagent could be used, and the reactions led to some recovered starting material. Thus we considered whether a new process was possible in which we would use both a tether and a template to direct halogenations. We decided to try to invent what we called a radical relay process. 

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