Partly bridged cavitands 2 and 4 can be selectively debrominated in one step by treatment with 5 equiv of n-BuLi in THF to afford the corresponding dibromo derivatives 5 and 6 in 90% and 77% yield, respectively. After incorporatin of the fourth bridge, the remaining two bromines can be replaced by CN to give 9 (95%), (C(O)OMe to give 10 (60%) or OH to give 11 (62%). Two molecules of 11 were coupled with CH2BrCl in DMSO/THF under high dilution conditions to give new hemicarcerand 12 in 71% yield.
Timmerman, P., van Mook, M. G. A., Verboom, W., van Hummel, G. J., Harkema, S., & Reinhoudt, D. (1992). Selective functionalization of cavitands: synthesis of a new hemicarcerand. Tetrahedron letters, 0(33), 3377-3380. https://doi.org/10.1016/S0040-4039(00)92093-8