Iminoesters imidazoles

In a related reaction a-amino ketones (175) with iminoesters RC(NH)OMe give imidazoles (175 — 176). 

In a related reaction, -amino ketones 241 with iminoesters 242 give imidazoles 243 (Scheme 117) (see also . 

Initially a-halo ketones (30) react with formamide to give iminoesters (31), which then either ring-close to the oxazoles (32) or decompose to form a-hydroxy ketones (33). The a-hydroxy ketones formed in this way react with excess formamide in the presence of liberated hydrogen halides or the added quantity of sulfuric acid to give a-formoxy ketones (34) which then yield the oxazoles (32) with formamide.10 95 On the other hand, a-hydroxy ketones and formamide in the absence of added sulfuric acid yield imidazoles (35) predominantly.92 Evidence for this reaction pathway came from the observations that a-formoxy ketones could be isolated, and reaction with formamide converted them into the oxazoles.94... 

In 1998, Herrmann et al. reported the synthesis of the first chiral carbene containing an oxazoline unit. In this bidentate ligand, the oxazoline ring is linked in its 2-position to the imidazole ring via a methylene bridge [48]. The key step in the synthesis of the imidazolium precursor is the acid-catalyzed cyclization of the oxazoline by reaction of an iminoester, formed in situ from a nitrile function, and the amino alcohol (Scheme 15.12). 

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