Amides, Sulfonamides and Carbamates

An intermolecular version of the arylation of carbamates has been recently published by Hartwig et al. (Eq. (21)) [132]. His group showed that reactions catalyzed by a combination of Pd(OAc)2 and P( -Bu)3 formed /V-aryl carbamates from aryl bromides or chlorides and f-butylcarbamate as substrate. Again, the reaction conditions were not as mild as those for amination, but were similar to those of the intramolecular reactions. For the intermolecular reactions, the use of sodium phenox-ide as base was crucial. Reactions using Cs2C03 showed low conversions. Those involving NaO-r-Bu as base rapidly formed a gel, presumably from the deproto-nated carbamate, and also showed little or no conversion. The products of these reactions serve as conveniently protected anilines, and r-butylcarbamate can be considered one type of ammonia surrogate. In addition, the products of these reactions are suitable for subsequent directed metalation procedures [100]. 

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A variety of N-H containing compounds are A-arylated by Ar3Bi in the presence of a stoichiometric amount of Cu(OAc)2, 155-161 which plays dual important roles it oxidizes Ar3Bi to Ar3Bi(OAc)2 and mediates the arylation via transmetallation (Equation (94)). In the presence of Et3N or pyridine, the Cu(OAc)2-promoted A-arylation of amides, sulfonamides, ureas, carbamates, and anilines with Ar3Bi occurs much more efficiently than the reaction without a... 

N-Arylaminophthalimides, hydrazines, hydrazones, and N-H containing heterocycles are N-arylated by combined use of Ar3Bi and Cu(OAc)2 (Scheme 14.134) [281] in which Cu(OAc)2 oxidizes Ar.l i to Ar jl i(OAc)2 and catalyzes the arylation via transmetalation (Section 14.3.4.2). The Cu(OAc)2-promoted N-arylation of amides, sulfonamides, ureas, carbamates, and anilines with ArsBi proceeds efficiently in the presence of EtsN or pyridine (Scheme 14.135) [282]. N-Arylation occurs selectively on the primary amino group of aminobenzanilides (Scheme 14.136) [283]. A variety of amines are N-alkylated in moderate yields by use of alkylbismuthanes assisted by Cu(OAc)2 [284]. 

Scheme 21 [Cp IrCl2]2-catalyzed amination of alcohols with ammonium salts, carbamates, amides, sulfonamides and primary heteroarylamines...

Apart from aryl esters and amides of carboxylic acids, aryl carbonates, and carbamates, other types of organic compound have been reported to undergo PFR. They include oxalates, formiates, sulfonates, sulfonamides, thioesters, selenoesters, and telluroesters. 

The scope of nitrolysis is huge, with examples of nitramine formation from the cleavage of tertiary amines, methylenediamines, carbamates, ureas, formamides, acetamides and other amides. The deflnition of nitrolysis must be extended to the nitrative cleavage of other nitrogen bonds because sulfonamides and nitrosamines are also important substrates for these reactions. The nitrative cleavage of silylamines and silylamides is also a form of nitrolysis (Section 5.7). 

When optically active allylic alcohol 6a and propargylic alcohol 6p were reacted with amides 2c and 2f, only racemic products 7ac, 7af, and 7pf were obtained (Scheme 2). The results suggested a mechanism through the formation of a carbe-nium intermediate. The observed racemization can also be ascribed to the reversibility of the present reaction. The result shown in Scheme 3 indicated that the reaction is reversible under the reaction conditions. When 7af was treated with 5 mol% of Bi(OTf)3 and KPF6 and 1 equiv of carbamate 2c, a mixture of 7af (28%) and 7ac (68%) was recovered after 1 h. The result suggested that Bi(OTf)3/KPF6 cleaved the C-N bond in 7af derived from sulfonamide 2f, and that 7ac is thermodynamically more stable than 7af. We assume that the desiccant (Drierite) had a beneficial effect on the reactions of substrates shown in Tables 10-12 because of the observed reversibility of the present reaction. In this reaction, the possibility... 

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