Structurally rigid and optically active dendrimers

Novel rigid and optically active dendrimers containing cross-conjugated uni ts are synthesized from the coupling of phenylacetylene-based dendrons with an optically pure diacetate of 4,4',6,6'-tetrabromo-1, 1'-bi-2-naphthol. T he UV and fluorescence spectroscopic studies demonstrate that there is a ve ry efficient energy migration from the cross-conjugated dendrons to the cen ter core, leading to greatly enhanced fluorescences at higher generations. This is the first example of an efficient energy migration conducted in an optically pure dendritic system, which is potentially useful in developing an enantioselective fluorescence sensor. The generation 2 dendrimer has bee n used to catalyze the asymmetric reaction of diethylzinc with aldehydes an d has shown high enantioselectivity in the presence of Ti(O-i-Pr)(4).