... 7) have repeatedly shown that they are complementary and could be used for multiple substitutions of diverse heterocycles. ... we have prepared (by literature procedures) a set of protected uracils 2–8 bearing diverse N-protecting groups ... g BBr 3 , m-xylene, reflux, 140 °C, 19 h. ...
[Kundu, Nitya G.; Sikdar, Sikha; Hertzberg, Robert P.; Schmitz, Scott A.; Khatri, Surenda G. Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1985 , p. 1295 - 1300]