  We study N=1 dualities in four dimensional supersymmetric gauge theories in
terms of wrapping D 6-branes around 3-cycles of Calabi-Yau threefolds in type
IIA string theory. We generalize the recent work of geometrical realization for
the models which have the superpotential corresponding to an $A_k$ type
singularity, to various models presented by Brodie and Strassler, consisting of
$D_{k+2}$ superpotential of the form $W=Tr X^{k+1} + Tr XY^2$. We discuss a
large number of representations for the field $Y$, but with $X$ always in the
adjoint (symmetric) [antisymmetric] representation for $SU (SO) [Sp]$ gauge
groups.
