Why are triflates so widely used in coupling reactions, but not tosylates, mesylates nor nosylates?
- As a result of the -I effect of the trifluoromethyl group, triflate is a better nucleofuge than mesylate and tosylate.
- As compared to tosylate and nosylate, triflate is rather small. This might be an advantage in reactions at "crowded" centres.
- Triflates do not undergo side reactions, such as hydrogen abstraction reactions, etc. A triflate, once introduced, can easily survive several steps in a synthesis.