Palladium(0)-catalysed allylation of uracils and thiouracils. Influence of the solvent on the regioselectivity of the allylation

Article abstract of DOI:10.1016/0040-4020(96)00486-3

Uracil and 5-substituted uracils are monoallylated at N-1 in H₂O- CH₃CN with the catalytic systemPd(OAc)₂/P(C₆H₄-m -SO₃Na)₃ (or tppts) although performing the reaction in H₂O/THF with the system Pd₂(dba)₃/dppb leads to diallylations at N-1 + N-3.2-Thiouracil, 5-methyl-2-thiouracil (2- thiothymine) and 6-methyl-2-thiouracil are monoallylated at sulfur in H₂O/CH₃CN with the catalytic system Pd(OAc)₂/P(C₆H₄-m-SO₃Na)₃ (or tppts). Performing the reactions in H₂O/THF with the system Pd₂(dba)₃/dppb leads to diallylations at N-1 + N-3 of 2-thiouracil and 2-thiothymine whereas 6-methyl-2-thiouracil is diallylated at S + N-3.