Sulfur-directed, selective ortho-functionalization of benzyl thioethers with maleimides has been achieved under a ruthenium-catalyzed system; herein, temperature and additive play a crucial role in determining product selectivity. The ortho-alkenylated maleimide proved thermally sensitive in the presence of Cu(OAc)2, whereas the presence of Zn(OAc)2 diverted the reaction pathway towards an exclusive ortho-alkylation. However, benzyl phenyl selenoethers afford selenated maleimide derivatives via C─Se bond cleavage under established reaction protocols.
Negi et al. (Wed,) studied this question.