Imidazole, formyl

Imidazole, 2-ethyl-1 -(o-nitrophenyl)-cyclization, S, 431 Imidazole, 4-ethyl-2-phenyl-oxidation, S, 405 Imidazole, ethynyl-Michael addition, S, 437 Imidazole, 4-ethynyl-2-phenyl-synthesis, S, 494 Imidazole, 1-formyl-reactions, S, 452 Imidazole, 2-formyl-mass spectra, S, 360 Imidazole, 4-formyl-synthesis, S, 475-476 Imidazole, 2-formyl-1,5-dimethyl-mass spectra, S, 360 3-oxide... 

Imidazole, 4-formyl-5-hydroxy-l-phenyl-mesoionic, 5, 372 Imidazole, 2-formyl-1-methyl-mass spectra, S, 360 Imidazole, 2-formyl-l,4,5-trimethyl-... 

Secondary amines such as dibenzylamine or 4-substituted piperidines are readily formylated in yields of up to 94% at room temperature by excess N,N-di-methylformamide (DMFj/MesSiCl 14/imidazole with formation of HCl and HMDSO 7 [32aj. 

Related redox transformations allow the conversion of ynals to a,P-nnsaturated esters [33], as well as the ring expansion of formyl P-lactams [34], oxacycloalkane-2-carboxaldehydes [35], and 2-acyl-1-formyIcyclopropanes [36], Farther developments allow the synthesis of amides from a range of a-fnnctionalised compounds, but require an additive (imidazole, HO At or HOBt) for efficient amidation [37],... 

The preparation of imidazolides by acylation of imidazole with acid chlorides is sometimes limited by the inaccessibility or instability of the required acid chlorides (e.g., formyl chloride, highly unsaturated acid chlorides, etc.) or by side-reactions in the case of multifunctional systems. For these reasons and due to the availability of an easy and convenient procedure involving very mild conditions, imidazolides today are usually prepared directly from the corresponding carboxylic acids with jV -carbonyldiimida-zole (CDI) or one of its analoga (see page 16). Use of these reagents has become more and more the preferred method for activation of carboxylic acids to azolides and their further transacylation to esters, amides, peptides, etc. (see subsequent Chapters). 

It seems reasonable to assume that the open-chain compound 5-(formyl-amino)-4-[(A -/3-aminoethyl)formamidino]imidazole (70) is intermediate for the formation of both products 68 and 69. RecycUzation can occur to either the N -derivative 68 or to 5-(formylamino)-4-(2-aminoimidazolin-2-yl)imidazole (71). A subsequent internal cyclization between the NH group and the carbonyl functionality gives the ethano derivative 69 (Scheme IV.30). Support for this mechanism comes from the observation that adenosine 67, being N-labeled on the 6-amino group, yields unlabeled 69 [95H(41)1399]. 

Agonist analogs of TRH have been synthesized, showing that the n electron system and the basic imidazole ring are necessary for activity the N-formyl-Pro-Met-His-Pro-NHj (5.69) has 40% of the full activity of TRH but is resistant to serum inactivation. Some... 

Imidazol und einfache Alkyl-imidazole besitzen im UV-Spektrum im Bereich > 200 nm nur Banden mit geringer Extinktion. Durch Aryl-Substituenten oder funktionclle Gruppen (z.B. Formyl, Nitro) steigt die Absorbtion betrachtlich68 ... 

Nitro-imidazoi AmajI = 298 nm logG = 3,80 4-Formyl-imidazol 2mail = 256 nm loge = 4,07... 

Zu Imidazolen ohne Hetero-Substituenten in 5-Stellung fuhrt die folgende Variante Das oc-(Alkoxymethyliden-amino)-carbonsaure-nitril wird mit Natriumethanolat und Ameisensaure-ethylester zum Enolat des entsprechenden a-Formyl-Derivates kondensiert und dieses dann in einer Eintopfsynthese mit Ammoniumsulfat zum 4(5)-Cyan-imidazol, z.B. 4(5)-Cyan-2-phenyl-imidazol bzw. 2-Benzyl-4(5)-cyan-imidazol cyclisiert250,251. 

Die durch Fluorid-Ionen induzierte Cyclisierung von Dichlor-essigsaure-[N-(2-trimethylsilyl-oximino-propyl)-anilid] fiihrt direkt zu 2-Formyl-4-methyl-l-phenyl-imidazol-3-oxidni. Die eigentlich erwartete 2-Dichlormethyl-Verbindung konnte nicht isoliert werden. 

Aus 2-Alkylidenamino-3,3-dichlor-acrylnitrilen und 2-Formyl-thiophenen werden unter Hydrolyse der nicht isolierten 4(5)-Chlor-5(4)-dichlormethyl-2-(2-thienyl)-imidazole direkt die entsprechenden 4(5)-Chlor-5(4)-formyl-2-(2-thienyl)-imidazole isoliert323. 

Formyl-imidazole decarbonylieren beim Kochen in Ethanol mit katalytischer Menge Siiure. Mit einem Saure-UberschuB erha.lt man dagegen die entsprechenden Acetale564. 

Unter Katalyse mit Kupfer-Pulver ist sogar die Substitution des Brom-Atoms im relativ elek-tronenreichen 4-Brom-2-formyl-thiophen durch Imidazol zu l-(2-Formyl-4-thienyl -imidazol (74%) moglich775. 

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