protection of tertiary amine while epoxidize an alkene.

1. use NaHSO3 to reduce the amine oxide.

tert-amine can be oxidized by mcpba to amine oxide. by using NaHSO3, the oxide can be reduced to tert-amine again. So use 2 eq. mcpba , then treated with NaHSO3.

2. TFA protection.
use TFA to convert the tert-amine to TFA salt which prevented oxidation.
after mcpba, use K2CO3 to remove TFA.
this method is not good to acid sensitive compound.