1-alkyl-2-aryl-5-chloroimidazoles

Five‐Membered Heterocycles: 1,3‐Azoles

“…This method was discovered by Wallach [34][35][36] and elaborated by Sarasin [37]. This approach, initially limited to methyl and ethyl symmetrical disubstituted oxamides, was extended to higher symmetrical [34,38,39] and unsymmetrical N,N 0 -disubstituted oxamides (Scheme 10.7) [40]. In the latter case, to obtain appreciable regioselectivity very dissimilar substituent (alkyl versus aryl) should be used.…”

Polychloroheteroaromatic Compounds

“…I Me of these two compounds and the trichloro-derivative (321; R = Me) is obtained when a larger quantity of phosphorus pentachloride is used in phosphorus oxychloride [705]. This Wallach-type synthesis of imidazoles has been extended to the preparation of other chloro-imidazoles [706,707]. A mixture of 4,5-dichloro-and trichloro-1-methylimidazole (321; R = Me) is obtained on further chlorination of 2-chloro-1-methylimidazole with chlorine in phosphorus oxychloride [708] or with a mixture of phosphorus pen tachloride and phosphorus oxychloride [709].…”

Imidoyl Halides

“…The reaction ofN-alkyl-N'-arylmethyloxamides XXV with phosphorus pentachloride to yield l-alkyl-2-aryl-5-chloroimidazoles (XXVI) proceeds via imidoyl chloride intermediates (124 (42,64,275,281), and carbonyl chloride e0 7 ,109,110,140,223,239,264,281) have been used to synthesize imidoyl halides or iminium halides, respectively. The reaction proceeds via an initial complex formation, followed by elimination.…”