Isopropyl-2,5-dimethylimidazole

Another reaction which proceeds through an intermediate amidine is that in which 4-foimylimidazoles are made from 5-aminopyrimidine and an N-substituted imidoyl chloride in the presence of phosphoryl chloride. Once the intermediate amidine has formed, the pyrimidine ring opens up. Yields, however, are rather low ( 25%) [45]. 

A mixmre of acetaldoxime (20.0 g, 0.34 mol) and butanedione monoxime (34.2 g, 0.34 mol) is warmed to give a homogeneous solution, then allowed to stand at room temperature (2 days), refluxed (1 h), cooled, and diluted with diethyl ether (500 ml). The product precipitates as a tan solid (30.4 g, 63%), m.p. 194 C (dec.). Similarly prepared in 65% yield is 2-ethyl-l-hydroxy-4,5-dimethylimidazole 3-oxide. 

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A novel imidazole synthesis utilizes the salt IV-isopropylacetonitrilium tetra-chloroferrate (8) in condensation with an amino acid ester. The salt is readily made from acetonitrile, ferric chloride and isopropyl chloride. For example, with norvaUne methyl ester a 40% yield of 5-hydroxy-l-isopropyl-2-methyl-4-propylimidazole results. The reaction is believed to proceed via an intermediate amidine. Similarly, 1-isopropyl-2,5-dimethylimidazole is formed when (8) reacts with propargylamine (Scheme 4.1.5) [43, 44). 

A similar carbene complex was obtained from the reaction of (Me4C5H)2Mg with l,3-di-isopropyl-4,5-dimethylimidazol-2-ylidene, with a structure in the solid state that is closely related to that of 145 . ... 

Trifluoro-l,3,5-triazine 55 reacts with 2,3-dihydro-l,3-isopropyl-4,5-dimethylimidazol-2-ylidene tetrafluoroborate 136 resulting in replacement of one fluorine atom to yield difluoro-l,3,5-triazine 137 (Scheme 55) [8],... 

Scheme 55 Interaction of 55 with 2,3-dihydro-l,3-isopropyl-4,5-dimethylimidazol-2-ylidene tetrafluoroborate 136...

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