Imidazole 3-oxide 1.4.5- trimethyl

If the 2-position possesses a substituent, hydrogen atoms situated at lateral positions at C3 and C4 can be replaced with an acyl group. Thus 2,4,5-trimethyl-imidazole 1-oxide 291 reacted with acetic anhydride to give a 4.3 1 mixture of the 3-acetoxymethyl 292 and 5-acetoxymethyl-imidazoles 293 (2010UP1) (Scheme 87). 

Durch Reduktion von 1-Hydroxy-2,4,5-trimethyl-imidazol-3-oxid mit Natriumhydrogensulfit wird 2,4.5-Trimethyl-imidazol in 20% Ausbeute erhalten510. 

Trimethyl-imidazole 1-oxide 263 could be nitrated at the 2-position. According to reaction kinetics it is the neutral imidazole species which undergoes nitration (1977JCS(P1)672) (Scheme 82). 

Imidazole, 2,4,5-trichloro-1-methyl-chlorination, 5, 398 Imidazole, 2,4,5-trideutero-iodination, 5, 401 Imidazole, 1-trifiuoroacetyl-reactions, 5, 451-452 Imidazole, 2-trifiuoromethyl-hydrolysis, 5, 432 Imidazole, 2,4,5-triiodo-nitration, 5, 396 synthesis, 5, 400 Imidazole, 1,2,4-trimethyl-photolysis, 5, 377 rearrangement, 5, 378 Imidazole, 1,2,5-trimethyl-photochemical rearrangement, 5, 377 rearrangement, 5, 378 Imidazole, 1,4,5-trimethyl-bromination, 5, 399 3-oxide... 

Reaction of trisubstituted imidazole N-oxides such as l,4,5-trimethylimidazole-3-oxide 930 with 18/NEt3 in CH2CI2 at 0-5 °C affords the l,4,5-trimethyl-2-cyano-... 

Imidazole, l,2,5-trimethyl-4-nitro-mass spectra, 5, 359 Imidazole, 1-trimethylsilyl-reactions, 5, 454 with acid chlorides, 5, 391 Imidazole, 1-trimethylstannyl-reactions, 5, 454 Imidazole, 2,4,5-trinitro-reactions, 5, 98 synthesis, 5, 395 Imidazole, 1,2,4-triphenyl-UV spectra, 5, 356 Imidazole, 1,2,5-triphenyl-UV spectra, 5, 356 Imidazole, 2,4,5-triphenyl-chemiluminescence, 5, 381, 406 irradiation, 5, 433 oxidation, 5, 376, 406 photochemical addition reactions, 5, 421 synthesis, 5, 467, 483 UV spectra, 5, 356, 357 Imidazole, 1-trityl-rearrangement, 5, 377 Imidazole, vinyl-Michael addition, 5, 437 polymers, 1, 281 Imidazole, 1-vinyl-reactions, 5, 450 thermal rearrangement, 5, 450 Imidazole, 2-vinyl-oxidation, 5, 437 Imidazole, l-(D-xylofuranosyl)-synthesis, 5, 491 277-Imidazole, 2,2-dialkyl-rearrangement, 5, 422 277-Imidazole, 4,5-dicyano-2,2-dimethyl-synthesis, 5, 472... 

Of the substituted pyridines, the halogenated derivatives have been the most intensively studied.144,145 Treatment of 3,5-dichloropyridine A-oxide at 74° with 0.1 A NaOD led to exchange in three positions of the molecule, whereas with 3-chloropyridine iV-oxide relative rates of exchange were position 2>6>4>5. In l-methyl-4-pyridone, 1,3,5-trimethyl-4-pyridone, and 3,5-dibromo-l-methyl-4-pyridone, deuteration in basic D20 at 100° gives 2- and 6-substitution.146 With the poly-azaindenes (45) -(47) already discussed in the acid exchange section,141 base-catalyzed deuteration occurs in the positions indicated 45 3 and 5 46 2, 3, 5, and 6 and 47 2, 5, 6, and 7. In other isolated heterocycles some selectivity is observed in base-catalyzed exchange, e.g., certain imidazoles,147 thiazole,148 isothiazole,148 benzothiazole,149 and benzoxazole.149... 

Alkaline cleavage of 2,4,4-trimethyl-5-phenyl-4//-imidazole 1-oxide gives oximes of a-acylaminoketones as products (80AHC(27)24l). 

A regiospecific synthesis of A -substituted (aminopyridinyl)imidazole 1286 started with ketone 1282 (cf. Section 4.02.9.2(i)). a-Oximination of ketone 1282 with isoamyl nitrite under basic condition provides oxime isomers 1283. Both as- and /ra t-oximes 1283 participate in the cyclization process when treated with l,3,5-trimethyl-l,3,5-triazinane, leading to imidazole iV-oxide 1284 that is then reduced with 2,2,4,4-treta-methyl-cyclobutane-l,3-dithione to give 1285 (Scheme 326) <2003JOC4527, 1999JME2180> (see also Section 4.02.9.3(i)). 

The mass spectrum of I-methyl-4-nitroimidazole-5-carboxylic acid amide shows the elimination of water by an electron impact as distinct from the usual thermal process. In l,4,5-trimethylimidazole-2-carboxylic acid the principal loss is that of CO2. Subsequent loss of O, OH, and HCN was also observed (Schofield et al., p. 173). Ferguson and Schofield (pp. 172,173) have reported considerable data for imidazole JV-oxides. Thus 1-methoxy-4,5-dimethyl-2-phenylimidazole (which loses OCH3 and CH3CN from the fragment m/e 171) is readily distinguished from l,4,5-trimethyl-2-phenyl-imidazole 3-oxide (loss of O and OH). The spectra of 1-benzylimidazoles are dominated by the tropylium ion. ... 

The thermal rearrangement of 2,4,4-trimethyl-5-phenyl-4if-imidazole 1-oxide to 2,4,4-trimethyl-l-phenyl-2-imidazolin-5-one appears to involve a phenyl migration, while alkaline cleavage gives oximes of a-acyla-minoketones." ... 

Diaza-compounds. The pyrrolo-pyrazole derivative (705) is one of the products of the action of acids on the tosylhydrazone H2C=CMe(CH2)2CH=N—NHTos. The reaction of 2,5,5-trimethyl-l-pyr-roline iV-oxide (706) with the ketenimine Ph2C=C=NPh yields the pyrrolo-imidazole (707)/ Pyrazolidin-3-one and 3-chloropropanoyl chloride combine to form the dioxopyrazolopyrazole (708)/ Irradiation of l-(o-iodoben-zoyl)imidazole (709 R=H) produces the indolobenzimidazolinone (710) the... 

Indole contains a pyrrole ring fused with a benzene ring. Compounds derived from indole include the essential amino acid L-tryptophan (Section 27.1C) and the neurotransmitter serotonin. Purine contains a six-membered pyrimidine ring fused with a five-membered imidazole ring. Caffeine is a trimethyl derivative of an oxidized purine. Compounds derived from purine and pyrimidine are building blocks of deoxyribonucleic acids (DNA) and ribonucleic acids (RNA, Chapter 28). 

---