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Protecting Groups for Indoles, Pyrroles, and Imidazoles

Sulfonamides (R2NSO2R ) are prepared from an amine and sulfonyl chloride in the presence of pyridine or aqueous base. The sulfonamide is one of the most stable nitrogen protective groups. Arylsulfonamides are stable to alkaline hydrolysis, and to catalytic reduction they are cleaved by Na/NH3, Na/butanol, sodium naphthalenide, or sodium anthracenide, and by refluxing in acid (48% HBr/cat. phenol). Sulfonamides of less basic amines such as pyrroles and indoles are much easier to cleave than are those of the more basic alkyl amines. In fact, sulfonamides of the less basic amines (pyrroles, indoles, and imidazoles) can be cleaved by basic hydrolysis, which is almost impossible for the alkyl amines. Because of the inherent differences between the aromatic — NH group and simple aliphatic amines, the protection of these compounds (pyrroles, indoles, and imidazoles) will be described in a separate section. One appealing proj>erty of sulfonamides is that the derivatives are more crystalline than amides or carbamates. [Pg.379]

Two new sections on the protection for indoles, imidazoles, and pyrroles, and protection for the amide — NH are included. They are separated from the regular amines because their chemical properties are sufficienth different to affect the chemistry of protection and deprotection. The Reactivity Charts in Chapter 8 are identical to those in the first edition. The chart number appears beside the name of each protective group when it is first discussed. [Pg.475]

MO-Acetals afford robust protection for indoles and pyrroles with SEM and BOM ethers being particular favourites. A SEM group has also been used to protect imidazole.534 They are introduced in much the same way as already discussed for amines and amides in section 8.6. L Hence treatment of Indolelactam derivative 274.1 with SEMC and sodium hydride in THF at —15 °C afforded the M 0-acetal 274 in >80% yield 535... [Pg.534]

Reagent for the Protection of Secondary Amines. SEM-Cl can be used to protect secondary aromatic amines (eq 13), and is an ideal reagent for the protection of imidazoles, indoles, and pyrroles (eqs 14-16). Many functional groups are compatible with the introduction and cleavage of SEM amines, and the SEM substituent is unusually stable to further functionahzation of the molecule. " Recently, a one-pot method for protection and alkylation of imidazoles employing w-butyllithium and SEM-Cl has been developed (eq 17). ... [Pg.629]


See other pages where Protecting Groups for Indoles, Pyrroles, and Imidazoles is mentioned: [Pg.447]    [Pg.531]    [Pg.487]    [Pg.623]    [Pg.447]    [Pg.531]    [Pg.487]    [Pg.623]    [Pg.461]    [Pg.503]    [Pg.604]   


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Imidazole groups

Imidazole protecting groups

Indole protection

Indole pyrrole

Indoles pyrroles

Protecting group for pyrrole

Protecting groups for

Protective groups for

Pyrrole protection

Pyrroles and indoles

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