The reactivity of uracil derivatives bearing acidic methylene groups a
t N1 was investigated. On treatment with strong base, compounds with n
itrile as the activating group underwent extensive dimerisation to giv
e new tricyclic systems. Ester-activated compounds also produced dimer
s in the absence of an external electrophile, but their monomeric carb
anions could be trapped by prompt addition of benzyl bromide to give n
ormally alkylated products.