Protection for Imidazoles, Pyrroles, Indoles, and other Aromatic Heterocycles

PROTECTION FOR IMIDAZOLES, PYRROLES, INDOLES, AND OTHER AROMATIC HETEROCYCLES  

Protective group chemistry for these amines has heen separated from the simple amines because chemically they hehave quite differently with respect to protective group cleavage. The increased acidity of these aromatic amines makes it easier to cleave the various amide, carbamate, and sulfonamide groups that are used to protect this class. A similar situation arises in the deprotection of nucleoside bases (e.g., the isobutanamide is cleaved with methanolic ammonia ), again, because of the increased acidity of the NH group. 

2% KOH, H2O, reflux, 12h, 64-92% yield. This group is more stable to n-BuLi than is the benzyl group when used to protect imidazoles. 

73% yield. TFA, TfOH, rt was also effective in this case (89% yield). 

The methanesulfonamide is prepared by reaction of the amine with MsCl and TEA in CH2CI2. 

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Protection for Imidazoles, Pyrroles, Indoles, and Other Aromatic Heterocycles 872... 

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