  Let $G$ be a group and $R,S,T$ its normal subgroups. There is a natural
extension of the concept of commutator subgroup for the case of three subgroups
$\|R,S,T\|$ as well as the natural extension of the symmetric product $\|\bf
r,\bf s,\bf t\|$ for corresponding ideals $\bf r,\bf s, \bf t$ in the integral
group ring $\mathbb Z[G]$. In this paper, it is shown that the generalized
dimension subgroup $G\cap (1+\|\bf r,\bf s,\bf t\|)$ has exponent 2 modulo
$\|R,S,T\|.$ The proof essentially uses homotopy theory. The considered
generalized dimension quotient of exponent 2 is identified with a subgroup of
the kernel of the Hurewicz homomorphism for the loop space over a homotopy
colimit of classifying spaces.
