Neue Darstellungsweise substituirter Imidazole

Modular Synthesis of Tetrasubstituted Imidazoles and Trisubstituted Oxazoles by Aldimine Cross‐Coupling

“…Imidazolium salts can be used as ionic liquids or as precursors of versatile N‐heterocyclic carbenes 11. Commonly used methods for the construction of the imidazole ring12, 13 include cyclocondensation reactions between α‐diketones, α‐hydroxy ketones, α‐haloketones, or α‐aminoketones and formamide (Bredereck synthesis),14 the reaction of α‐diketones with aldehydes and ammonia according to Japp, Robinson, and Radziszewski15, 16 and the reaction of α‐haloketones with amidines 17. The formal cycloaddition of tosylmethyl isocyanide (TosMIC) and its substituted derivatives to aldimines (van Leusen reaction) is a less frequently encountered method that involves the formation of the C4C5 bond 18.…”

Ikaros expression as a marker for lymphoid progenitors during zebrafish development

“…2,4(5)‐Diarylimidazoles were also regioselectively synthesized in modest‐to‐good yields by direct C‐2 arylation of 4(5)‐arylimidazoles with activated and unactivated aryl bromides and iodides in DMF at 140 °C in the presence of a catalytic amount of Pd(OAc) 2 and 2 equivalents of CuI under base‐free and ligandless conditions (Scheme ) 17b…”

“…As a result, a number of methodologies for the preparation of variously substituted imidazoles has been intensively developed 14. Methods for imidazole core synthesis include cyclocondensation reactions of α‐hydroxy ketones, α‐amino ketones with formamide (Bredereck synthesis),15 the base‐promoted reaction of tosylmethyl isocyanide (TosMIC) and its substituted derivatives with aldimines, polymer‐bound imines or imidoyl chlorides (van Leusen reaction),16 reaction of amidines with α‐halo ketones,17 reaction of α‐diketones with ammonia and aldehydes (Debus–Radziszewski reaction),18 condensation of α‐hydroxy ketones with aldehydes and AcONH 4 in the presence of diacetoxyiodobenzene,19 reaction of α‐(hydroxyimino) ketones with 1,3,5‐trisubstituted hexahydro‐1,3,5‐triazines,20 cyclization reaction of α‐halo ketones and N ‐acetylguanidine,21 treatment of the sodium enolate salts of N ‐acyl‐ C ‐formylglycine esters with acid and KSCN,22 pyrolysis of α‐azido ketones,23 condensation of α‐amino ketals with imidates followd by cyclization in refluxing 4 M HCl/dioxane,24 treatment of N ‐monosubstituted amidines with 2‐halo‐3‐alkoxy‐2‐propanals,25 reaction of 3‐bromo‐2‐isocyanoacrylates and primary amines,26 hetero‐Cope rearrangement of the adducts obtained by treatment of oximes with benzenecarboxyimidoyl chlorides followed by acid treatment of the resulting amidines,27 reaction of N ‐(2‐ oxo)amides with neat CF 3 COONH 4 under neutral conditions,28 treatment of α‐acylaminoimines with PCl 5 ,29 cyclization of N ‐alkyl‐ N ‐(β‐keto)amides with AcONH 4 and glacial AcOH,30 and cyclization of α‐( N ‐acyl‐ N ‐alkylamino)‐β‐ketoamides on Wang resin in the presence of AcONH 4 and AcOH 31. On the other hand, in 2005, a variety of 1,2,4,5‐tetrasubstituted imidazoles 7 were prepared using a facile solid‐phase synthesis involving: i) condensation of the polymer‐supported phenylsulfinic acid ( 1 ) with an aldehyde 2 and a carboxamide 3 ; ii) and traceless product release from the resulting compound 4 by a one‐pot reaction with an aldehyde 5 in the presence of a thiazolium catalyst and an excess of Et 3 N, followed by treatment with an amine 6 and acetic acid under reflux (Scheme ) 32…”

Bis(α‐bromo ketones): Versatile Precursors for Novel Bis(s‐triazolo[3,4‐b][1,3,4]thiadiazines) and Bis(as‐triazino[3,4‐b][1,3,4]thiadiazines)

“…α‐Bromo ketones are valuable compounds, which are useful in the synthesis of a variety of heterocycles as well as in other synthetic applications including cross aldol condensations , enaminoketones and Favorskii rearrangements …”