Synthesis of molecular chains: phenylene thioether and sulfoxide oligomers

The application of a general synthetic approach to prepare molecular chains is reported. It is based on a step-by-step method each consisting first in a Pd-catalyzed reaction between ArI and HXAr′Br (Ar=aryl, Ar′=arylene) to give ArXAr′Br followed by a Cu-catalyzed replacement of Br by I to give ArXAr′I that can be reacted with HXAr′Br in the following step. The application of this method is here illustrated to prepare phenylene sulfide oligomers (X=S). Starting from RC6H4I-4 (R=H, MeO, NO2, NH2) and HSC6H4Br-x (x=2, 4) it is possible to grow chains in one direction to give X(C6H4S-m)nC6H4R-4 (n=1, X=Br, m=4, R=H, MeO, NO2, NH2, SMe and m=2, R=H, MeO, NO2; n=1, X=I, m=2 or 4, R=H, MeO, NO2; n=2, X=Br, m=2 or 4, R=H, MeO, NO2; n=2, X=I, m=4, R=MeO, NO2; n=3, X=Br, m=4, R=MeO, NO2; n=3, X=I, m=4, R=NO2 and n=4, X=Br or I, m=4, R=NO2). From HSC6H4Br-x and IC6H4I-4 the chains can grow in two directions to give X(C6H4S-4)nC6H4X-4 (n=2 or 4, X=Br or I), 2-XC6H4(SC6H4-4)nSC6H4X-2 (n=3 or 5, X=Br). Using diiodomesitylene the dithioethers C6HMe3-2,4,6-(SC6H4X-4)2-1,3 (X=Br, I) have been prepared. The series of sulfoxides X(C6H4S(O)-4)nC6H4R-4 (X=Br, n=1, R=MeO, n=3, R=NO2, n=4, R=Br; X=R=I, n=2) has been obtained from the corresponding thioethers and PhICl2.