Alkylation of thymine with 1,2-dibromoethane

Alkylation of thymine with 1,2-dibromoethane depends strongly on the reaction conditions. Various alkyl derivatives may be produced, including N-1- or N-3-monosubstituted alkylthymines and products of their cyclisation, as well higher molecular weight products resulting from intermolecular substitution of N-1- and N-3-mono- and N-1,N-3-dialkylthymines. We have identified two cyclic products 5 and 6 and the dialkylated derivative 7, for which detailed structural analyses have been performed.