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DuP 532 (2), which is a potent angiotensin II receptor antagonist, has been prepared by two different routes. One route, which is more practical for large-scale synthesis, required the preparation of methyl 4(5)-(pentafluoroethyl)-2-propylimidazole-5(4)-carboxylate (9). This imidazole war synthesized in five steps from commercially available 11 in 32% overal yield. Alternate perfluoroalkylation methods of the iodoimidazole precursor 14 are presented. Imidazole 9 is remarkably stable to basic conditions and is alkylated by 2-[N-(triphenylmethyl)tetrazol-5-yl]-4'-(bromomethyl)-1,1'-biphenyl (8), giving only the desired regioisomer. A comparison of the alkylation of the trisubstituted precursors and analogues to 9 with 8 indicate that even under mildly basic conditions (K 2 CO 3 /DMF), the mechanism is S E 2cB (anionic), except for 2-propyl-4(5)-(hydroxymethyl)imidazole (11) which alkylates as a neutral species (S E 2') |
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