Designer Dendrimers: Branched Oligosulfonimides with Controllable Molecular Architectures

The synthesis of “designer” dendrimers and dendrons with sulfonimide units at every branching
point is reported. The synthesis is based on a series of (regio)selective functionalization reactions of amines
and sulfonamides allowing precise control of the dendrimers' shape, the number of branches in each
generation, and their peripheral decoration with functional groups. In principle, structurally different branches
can be incorporated at any position within the dendrimer structure at will. Structurally perfect symmetrical
and two-faced “Janus”-type dendrimers, as well as dendrimers and dendrons with intended interstices
were synthesized on a preparative scale and fully characterized. Oligosulfonimide dendrons of various
generations bearing an aryl bromide functional group at their focal points were attached to a p-phenylene
core with the aid of Suzuki cross-coupling reactions resulting in dendrimers with photoactive terphenyl
cores. The structure and the high purity of all dendritic sulfonimides were confirmed by means of 1H and
13C NMR, electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. The utility of MALDI-TOF mass spectrometry for the analytical characterization of these dendrimers was evaluated in comparison
to electrospray ionization. Two model branched oligosulfonimides were characterized in the solid state by
single-crystal X-ray analysis. Reaction selectivities and conformation of sulfonimide branching points were
rationalized by DFT calculations.