Benzimidazolinones, synthesis

Benzimidazolinone, 1,3-dimethyl-Friedel-Crafts reaction, 5, 429 Benzimidazolinone, 1,3-divinyl-synthesis, 5, 393 Benzimidazolinone, 6-methyl-Friedel-Crafts reaction, 5, 429 Benzimidazolin-2-one polymers, 1, 281 Benzimidazolinones alkylation, 5, 390 Friedel-Crafts reaction, 5, 429 Mannich reaction, 5, 390 nitration, 5, 429 reactions, 5, 442... 

A facile method for the synthesis of N-substituted 2-benzimidazolinones 142 has been developed by Romero et al. (96TL2361) using A-substituted ureas 139, which are cyclized to 142 with IBTA as an oxidant. The reaction probably proceeds via intermediates 140 and 141. Besides the iV-alkyl or aryl substituent, presence of the 1-methoxy group is necessary for the success of this cyclization. Another benzimidazoles synthesis involves cycli-zation of N-phenyl-C-alkyl formimidamides with IBD [95JCS(P1)615]... 

In essence, the synthesis of pimozide lies in the A(-alkylation of 4-(2-benzimidazolinon)piperidine (6.6.4), which is synthesized by the reduction of 1-(1,2,3,6-tetrahydro-4-piridyl)-2-benzimideazolone (6.3.10) using hydrogen over Raney nickel of pimozide (6.6.5), by the earlier synthesized 4,4-fc/x-(4-fluorophenyl)butylchloride (6.6.3). 

Despite the typical use of the 1,5-dienic system in the hetero-Cope rearrangement the participation of triple bonds, C=N and C=C, in the [3,3]-sigmatropic rearrangement was also reported. Synthesis of A-substituted benzimidazolinones 175 by a hetero-Cope rearrangement of the adduct 174 formed by reaction of A-arylhydroxamic acids 172 with cyanogen bromide 173 in the presence of triethylamine and at low temperatures was reported by Almeida, Lobo and Prabhakar (equation 51). 

Romero and coworkers employed FIFA, in the synthesis of PNU-95666E, a selective high-aflinity agonist at the dopamine D2 receptor, by successive nitrenium ion cycliza-tions (Scheme 14). Nitrenium ion cyclizations converted 62 to the lactam 63 which, after reductive demethoxylation to 64, protection as 65 and Af-functionaUzation, afforded the hydroxamic ester (66). A second cyclization with FIFA afforded the benzimidazolinone (67), which was readily reduced to the product 68 in overall yield of 26%. ... 

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