220 ± 0.5
14  cyc-propyl     182 ± 6
15  tert-butyl     230 ± 5
16  Ph     86 ± 3
17  4-OMe-Ph     79 ± 3
18  4-Me-Ph     87 ± 2
19  4-CN-Ph     53 ± 1
20  4-F-Ph     82 ± 3
21  4-Cl-Ph     97 ± 3
22