Selective n,n-dimethylation of primary aromatic amines with methyl alkyl carbonates in the presence of phosphonium salts.
In the presence of onium salts, at 140-170 degrees C, methyl alkyl carbonates [1a-c, ROCO2Me, R = MeO(CH2)2[O(CH2)2]n; n = 2-0, respectively] react with primary aromatic amines (XC6H4NH2, X= p-OMe, p-Me, H, p-Cl, p-CO2Me, o-Et, and 2,3-Me2C6H3NH2) to yield the corresponding N,N-dimethyl derivatives (ArNMe2) with high selectivity (up to 96%) and good isolated yields (78-95%). Phosphonium salts (e.g., Ph3PEtI and n-Bu4PBr) are particularly efficient catalysts. Overall, a solvent-free reaction is coupled with safe methylating agents (1a-c) made from nontoxic dimethyl carbonate.
Selva
Maurizio
M
Dipartimento di Scienze Ambientali dell'Università Ca' Foscari, and Consorzio Interuniversitario "La Chimica per l'Ambiente" (INCA), UdR di Venezia, Calle Larga S. Marta, 2137-30123 Venezia, Italy. selva@unive.it
Perosa
Alvise
A
Tundo
Pietro
P
Brunelli
Davide
D