We prove here the Martino-Priddy conjecture at the prime $2$: the $2$-completions of the classifying spaces of two finite groups $G$ and $G'$ are homotopy equivalent if and only if there is an isomorphism between their Sylow $2$-subgroups which preserves fusion. This is a consequence of a technical algebraic result, which says that for a finite group $G$, the second higher derived functor of the inverse limit vanishes for a certain functor $\mathcal{Z}_G$ on the $2$-subgroup orbit category of $G$. The proof of this result uses the classification theorem for finite simple groups.
49 , Conway's group Co3 and the Dickson invariants, Manuscripta Math. 85 (1994), 177–193. , Cohomology of sporadic groups, finite loop spaces, and the Dickson invariants, Proceedings of the 1994 Durham conference on Geometry and ...