Tetrahydropyran as a Protecting Group

4H-Pyran

The mechanism involves addition-elimination.

NO2

H

NO2

H

H

FNu-

NO2

H

NO2

H

HF Nu

NO2

H

NO2

H

HF Nu

NO2

H

NO2

H

HF Nu

NO2

H

NO2

H

H

Nu

+ F-

Carbodiimide Coupling