Imidazol 1.5-« pyridine-1.3-diones

More recently, a new and straightforward one-pot approach was reported by Bu et al. <2003JOC5415>. This reaction involves the cyclocondensation of l,2-dipyridin-2-yl-ethane-l,2-dione 120 and arylaldehydes, in the presence of ammonium acetate. Imidazo[l,5- ]pyridines 121 were obtained in reasonable yields, but competitive formation of imidazoles 122 was observed. The amount of ammonium acetate used in this reaction was also shown to strongly influence the yield of the cyclization (Scheme 38). 

Imidazol 1,2-0Ipyridine, 879, 13.39 Imidazol I..5-a pyridine, 874. 13.39 Imidazol 1,5-a Ipyridine, 1.321 lmidazo 4,5-6jpyridine, 741 Imidazol 1,2-a ipyridin-3-one. 1000 Imidazol 1,2-a pyridin-5-one. 917 Imidazol 1,2-ajpyridin-7-one. 918 Imidazo 4,5-6 pyridin-2-one. 1129 Imidazo 4.5-b)pyridin-2-one, 948 Imidazo 4,5-( pyridin-2-one, 1139 Imidazol 1,2-a]pyrimidine, 874 Imidazoll,2-( pyrimidine, 998, 1237 Imidazol 1,2-a pyrimidin-4-one, 1009 Imidazol 1,2-a pyrimidin-5-one, 1300 Imidazoj 1,2-a jpyrimidin-7-one, 1300 Imidazol 1.2-ajpyridin-7-one. 1106 Imidazoll,2-r quinazolin-5-one, 886 lmidazo 4,5-/ quina/olin-7-one, 684 lmidazo 4.5-/> quinazoiin-8-one, 1161 Imidazol 1,5-a Iquinoiine, 998 Imidazoj4.5-( quinoline, 1313 Imidazo 4..5-/Iquinoiine, 981. 989 Imidazo 4,5-/ quinolin-7-one. 684 Imidazol 1,2-a Iquinoxaline, 975 Imidazol 1.5.4-de quinoxaline, 776 Imidazol I 3,4-de quinoxaline-2.5-dione, 1000... 

Michael/Henry/dehydration/aromatisation reaction of 2-(2-oxoethyl) benzal-dehydes and nitroalkenes mediated by pyrrolidine to obtain polysubstituted naphthalene derivatives. DBU catalysed the conjugate additions of alcohols to ot,p-unsaturated nitriles, esters and ketones. Perhaps more important are the aza-Michael addition reactions of amines to a,p-unsaturated ketones, nitriles and esters. Recently, Costa, Vilarrasa and coworkers described the addition of lactams, imides, 2-pyridone, pyrimidine-2,4-diones and inosines to methyl propiolate and other similar compounds, DABCO and DMAP being the best catalysts. As mentioned before, tertiary amines give zwitterionic species with activated allynes. It was as early as 1932 when Diels and Alder used the reaction of pyridine with dimethyl acetylenedicarbojylate (DMAD) for the synthesis of heterocycles. The interception of the corresponding intermediate with Al-tosylimines and activated olefins provided access to l-azadienes ° and highly substituted butadienes (Scheme 2.6). When the quenching species of the zwitterionic intermediate is a 1,2-diketone, dibenzoyl maleates or cyclopentenedione derivatives could be obtained (Scheme 2.6). The interception of the zwitterionic species of N-methyl imidazole (NMI) and DMAD with ketenes to obtain unsaturated esters has also been shown. ... 

Scheme 2.14 Enantioselective synthesis of a building block (28) for aflatoxin Bi (1). Reagents and conditions a) AcCl, pyridine, 98% b) Hg0 HBp4 Si02,12, 49% c) 85, Pd(0), PPhs, toluene, reflux, 65% d) Zn(Cu), CI3CCOCI, THF, —50°C e) Zn, HOAc, A, 70% over two steps, quant ee f) HCl, acetone. A, 55% g) TBSCl, imidazole h) DIBAL-H, 80% over two steps i) l-(phenylthio) pyrrolidine-2,5-dione, PBU3, benzene, 80% j) m-CPBA, CH2CI2, —78°C k) pyridine, toluene, 110°C 1) CsF, CH3CN, 0°C, 96% over three steps...

Conventional methods have been used to prepare ribonucleoside analogues from 2-(l//)pyrazinone, 3,5-disubstituted pyridines (including a-anomers), 6-methyl-l,3-oxazine-2,4-dione and 6-methyluracil, 2-alkyl-4,5-dicarboxamido-imidazoles, 7-membered ring analogues (4) and (5) of uracil and tetrahydro-uracil [one diastereomer of (4) being the most potent inhibitor of cytidine deaminase yet discovered], 2-alkylthioadenine, 8-aza-3-deaza-guanine/ ... 

Hojo reported a selective synthesis of 4-(trifluoromethyl)imidazoles (Scheme 35) [49], The diketones, prepared from aldehyde dialkyl hydrazones via the hydrolysis of 3-(dialkylhydrazino)-l,l,l-trifluoro-2-aIkanone intermediates, were treated with 1,1-dimethylhydrazine to afford the adduct. These adducts were generally unstable even at room temperature and, thus, were immediately dehydrated using POCI3-pyridine to afford 3-aryl-l,l,l-trifluoropropane-2-,3-dione-2-dimethylhydrazone. Intramolecular cyclization of these hydrazones in refluxing toluene afforded the desired 4-(trifluoromethyl)imidazoles. 

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