A direct allylation of aromatic compounds using allylsilane, allylgermane, or allylstannane (1) and arylthallium bis (trifluoroacetate) has been developed. The actual transmetalation reagent for 1 in the reaction was proposed to be thallium (III) trifluoroacetate (2), which was produced together with diarylthallium trifluoroacetate by the disproportionation of arylthallium bis (trifluoroacetate).