Towards determiningφ1withB→D(*)D¯(*)

We present an isospin analysis of the decay modes $B\to D\overline{D}$, $D^{*}\overline{D}$, $D{\overline{D}}^{*}$, and $D^{*}{\overline{D}}^{*}$, which allows the determination of the final-state interaction phases. As these transitions have branching ratios of the order ${10}^{-4}$ or larger, they could be useful in detecting the $\mathrm{CP}$-violating phase ${\phi }_1\equiv \arg \left(-V_{\mathrm{cb}}^{*}{V}_{\mathrm{cd}}{V}_{\mathrm{tb}}{V}_{\mathrm{td}}^{*}\right)$ in the first-round experiments of a $B$-meson factory. The problem of penguin pollution may still be present. Once the Kobayashi-Maskawa matrix elements are known, it is possible to obtain the magnitudes and relative phases of hadronic matrix elements for $B\to D^{\left(*\right)}{\overline{D}}^{\left(*\right)}$. This will in turn lead to some information about the penguin pollution.