1.3-Dimethylbenzimidazolium iodide

Dimethylbenzimidazolium iodide with [(ri -cod)Rh(p.-OMe)2Rh(Ti -cod)] gives the carbene-based complex [(ri -cod)Rh(L)I], where L is 1,3-dimethyl-benzimidazol-2-ylidene (97JOM(532)261). Similar complexes are known (94JOM(481)89). 

Dimethylbenzimidazolium iodide serves as a starting material for free carbenes (99CEJ1931, 99JA10626, 00AGE541) and carbene complexes (99JOM(585)241). Thus, with palladium(II) acetate it gives [L Pdl ] where L is... 

Nucleophilic aroylation of 153 to give 7-aroyltriazolopyrimidines 157 was achieved by heating with aromatic aldehydes, NaH, and a catalytic amount of 1,3-dimethylbenzimidazolium iodide (DMBI). Treatment of 157 with NaOH/DMSO and then K3[Fe(CN)6] resulted in aryl migration to give 158 (85CPB1395). 

Esters. Aromatic aldehydes undergo oxidation on reaction with /t-nitroaniline, DBU, and 1,3-dimethylbenzimidazolium iodide in an alcohol. Apparently the benzimidazolium ylide is involved. 

Two methods for introduction of the benzoyl group at C-5 have been described (86H1243). The first involves the reaction between 5-chloro-1,2,4-triazine 70 and benzaldehyde in the presence of the catalyst 1,3-dimethylbenzimidazolium iodide (71) and sodium hydride. The C-nucleo-philic ylide 72 formed under these conditions reacts with 5-chloro-3-phe-nyl-l,2,4-triazine 70 to yield the 5-benzoyl-substituted 1,2,4-triazine 73, simultaneously regenerating the catalyst 71 (Scheme 44) (86H1243). 

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