New Members of the Cucurbituril Family

This section describes the preparation of CB[n] homologs (n= 5,7,8,10). We begin the discussion with a mechanistic hypothesis for CB[n] formation advanced by the Day and Isaacs groups [5,12], 

To access the unknown cucurbituril homologs, Kim and Day performed the CB[n]-forming reactions under milder conditions (100 °C, cone. HC1 75 °C, 9M H2S04) [12,15], Although CB[6] is still the major component of the reaction mixture, the 

CB[n] homologs (CB[5], CB[7], CB[8], and C B[ 101 CB[5]) can be readily isolated on the 10-100 g scale by straightforward - but time consuming - washing and recrystalliza-tion procedures that are detailed in Section 4.8.2. To date, CB[9] has not been isolated in pure form, although it has been detected as a minor component of the CB[n]-forming reaction mixture by mass spectrometry and 13C NMR spectroscopy [12,15], 

---