A Zwitterionic Ladder

Significance

The authors present the synthesis of the phosphonium- and borate-bridged zwitter­ionic ladder stilbenes 3 and 4 as well as their extended analogues 7 and 9. Treatment of the monoborylated biphenylacetylene 2 with Cy₂PCl or (t-Bu)₂PCl led to the bridged products via spontaneous cascade cyclization while the di­phenylphosphanyl group in 5 was not nucleophilic enough to yield the bridged product.