Table 4. Rate Effects of Changing the Location (a^a Series vs b Series) or the Presence (a^a Series vs c Series) of an Electron-Withdrawing Group (Carbonyl) within the Triyne Linker.

^aStructures 1a, 24a, and 26a are identical to 1, 24, and 26 given in Table 3.

^bR = CH₂CH₂OTBS.

^cThe k_rel values for 24a:1a:26a are 9000:400:1 (data from Table 3).