4 -Iodo-imidazole

Considerable confusion has existed in the literature since the publication of incorrect structural assignments of 4-iodo- and 4,5-diiodo-imidazoles over 60 years ago (28JPR33). Pauly believed these compounds to be the 2- and 2,4-isomers, respectively, and only recently were the assignments finally corrected (81JOC1781 87AJC1399). Those involved in the field should therefore be wary of many reported structures of bromo- and iodo-imidazoles. For example, 4- (not 2-) iodoimidazole reacted with bromine in chloroform to give 4-bromo-5-iodoimidazole (not the 4-bromo-2-iodo isomer), and there are many other examples (81JOC1781). 

The sUylation of aromatic or heteroaromatic compounds can be performed via magnesiated or lithiated intermediates, which can be accessed by hydrogen-metal or halogen-metal atom exchange. Thus, C-4 silylation of imidazoles is achieved from4-iodo imidazoles (eq 45), while C-2 silylated oxazoles are prepared by addition of TMSOTf to the lithiated oxazole (eq 46) interestingly, for this reaction, the employment of TMSCl as electrophile... 

Alkylation of the nitrogen occurs readily and is either via direct Sn2 or Sn2, depending on the basicity of the reaction mixture and the electrophile. Sterics of the iV-alkylating group with other substituents will also play a role. For example, 4(5)-iodo-imidazole is reported to yield the iV-tosyl compound in 69% yield. Fully deprotonated imidazole predominantly provides direct Sn2-type reactions and tends to provide less quatemization. Excellent yield of... 

Imidazole, 2-iodo-1-methyl-4-nitro-pK 5, 384 [Pg.28]

Imidazole, 1 -hydroxy-2,4,5-triphenyl-3-oxides reactions, S, 455 Imidazole, iodo-nitrodehalogenation, 5, 396-397 Imidazole, 1-iodo-reactions, S, 454 stability, S, 110 Imidazole, 2-iodo-synthesis, S, 401 Imidazole, N-iodo-, S, 393 reactions, 5, 454 Imidazole, 4-iodo-5-methyl-iodination, 5, 400 Imidazole, 2-isopropyl-4-nitro-N-nitration, 5, 351 Imidazole, 2-lithio-reactions, S, 106, 448 Imidazole, 2-mercapto-l-methyl-as antithyroid drug, 1, 171 mass spectra, 5, 358 Imidazole, 1-methoxymethyl-acylation, S, 402 Imidazole, 5-methoxy-l-methyl-reactions... 

Halogenation of 106 with triphenylphosphine, iodine, and imidazole provided the iodo derivative 109. On treatment with lithium aluminum hydride, 109 was converted into two endocyclic alkenes, 110 and di-O-isopro-pylidenecyclohexanetetrol, in the ratio of 2 1. Oxidation of 110 with dimethyl sulfoxide - oxalyl chloride afforded the enone 111.1,4-Addition of ethyl 2-lithio-l,3-dithiane-2-carboxylate provided compound 112. Reduction of 112 with lithium aluminum hydride, and shortening of the side-chain, gave compound 113, which was converted into 114 by deprotection. ... 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

Treating imidazole with iodine in an NaOH solution afforded the complete ring iodination product, 2,4,5-triiodoimidazole. 4-Iodoimidazole was then produced in 75% yield upon selective reductive deiodination, [5]. The same procedure converted 2-methylimidazole and 1-methylimidazole to 4(5)-iodo-2-methylimidazole [6] and 4(5)-bromo-l-methylimidazole [7], respectively. 

Whereas the synthesis of 2,2 -biimidazoles has been very well developed, that of 4,4 -biimidazoles has not. Pyne et al. revealed that the Pd(0)-catalyzed homocoupling of 4-iodo-l-(triphenylmethyl)imidazole (5a) or its 2-methyl analog 5b delivered the 4,4 -biimidazoles 6a and 6b, respectively [6],... 

Generally, the intermolecular Heck reaction between 2-iodo-, 4-iodo- and 5-iodo-l-methylimidazoles and olefins suffers from low yields (< 25%). Therefore, these transformations are of limited synthetic utility [29]. In one case, variable yields for adduct 62 (15-58%) were observed for the Heck reaction of 5-bromo-l-methyl-2-phenylthio-lf/-imidazole (61) and a large excess of methyl acrylate [42]. 

The indirect anodic oxidation of ketones 42 in ammonia - containing methanol using iodide as a mediator afforded 2,5-dihydro-IH-imidazols 44 via oxidation of the intermediate ketimine 43 to AT-iodo imine followed by elimination of HI to afford the nitrenium ion, which subsequently reacts with ketimine 43 to give the product 44 [73] (Scheme 23). 

Very good selectivity has also been achieved with iodinated imidazole derivatives, and thus the replacement of the 2-iodo group of 1-benzyloxy-methyT2,4,5-triiodoimidazole was achieved with n-BuLi in 99% yield (91JOC4296). 

The I/Mg-exchange reaction can be extended to the use of iodo-substituted pyridines uracils , purines" , imidazoles , quinolines, imidazo[l,2-a]-pyridines, pyrroles ... 

Treatment of methyl 4,6-0-benzylidene-2-benzyloxycarbonylamino-2-deoxy-3-0-(imidazole-l-sulfonyl)-a-D-glucopyranoside with tetrabutylammonium iodide in refluxing toluene (3 h) gave the corresponding iodo derivative in 90% yield [68] (Scheme 13). When... 

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