Halides iminoesters

Complementing the examples shown thus far is a wealth of chemistry capable of affecting the transformation of hydroxyl groups to halides. These include the use of iminoesters (Scheme 6.10) [30] and reagents such as methanesulfonyl chloride, which is commonly employed in the preparation of sulfonate leaving groups [31]. The latter example, highlighted in Scheme 6.21,... 

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... 

Halides from alcohols via iminoesters with inversion of configuration s. 11, 619 OH Hal... 

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