Endo-trig reactions

With endo-trig reactions, whether they work or not depends on the ring size.
^{Click the structures below to see how 5- and 6-membered rings behave:}

5-endo-trig	6-endo-trig

K. Gilmore and I. V. Alabugin, Chem. Rev., 2011, 111, 6513–6556.