Alkylation and acylation at a nitrogen atom

The sonochemical alkylation at a nitrogen atom appeared for the first time in a paper by Davidson et al A t)q)ical example is given in Eq. 48, and many others are known. With carbazole, the rate increase is high, ca. 50 times, but the presence of polyethylene glycol methyl ether as a PTC is necessary. Alkylation of macrocyclic amines was improved by sonication in the presence of potassium hydroxide (Eq. 49), and quatemization is avoided. A practically quantitative yield is observed, even without PTC, but in this particular case, a phase transfer autocatalytic mechanism is probable. o 

Various N-alkylations of aliphatic, aromatic, and heterocyclic amines, tetrazoles, and phenylacridine-9 Carboxylate were also described. 21,122 -phe copper complex 

An intramolecular alkylation leading to aziridines occurs with a p-chloro carbamate (Eq. 51, see p. 344). In a solid-liquid biphasic system, the organic precursor in hexane is sonicated in the presence of solid sodium hydroxide and catalytic amounts of TOAB.  

Sonication promotes the reaction efficiently even without PTC, with a result equivalent to that of the stirred PTC reaction. The slow rate, however, requires long irradiation times, and hydrolysis of the carbamate becomes substantial. 

The N-alkylation of amides (Ch. 9, p. 339), e.g., acetanilide, was reported in a biphasic water-benzene system in the presence of TBAB. 25 With sodium hydroxide, irradiation for 3 h at room temperature leads to a 95% yield. The syntheses of N,N -dialkyl thioureas (no base mentioned),i26 and medium ring cyclic sulfonamides 27 re shown in Fig. 19. In the latter case, an autocatalytic effect analogous to the example of Eq. 48 is probable. 

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