Ethoxy-2-phenylimidazole

4-Ethoxy-2-substituted imidazoles, too, can be made from acylglycinamides in yields of 10-35% [13]. Modification of the reaction conditions by the use of triethyloxonium fluoroborate to induce cycUzation has led to the formation of 4-ethoxy-2-phenylimidazole in 80% yield [14]. 

A mixture of triethyloxonium tetrafluoroborate (14 g, 74 mmol) and hippuric amide (12g, 67mmol) in dichloromethane (100ml) is stirred for 7 days at 

One of the more common methods of benzimidazole synthesis is that which cyclizes o-arylenediamines in which one of the amino groups has been acylated or thioacylated. The starting material must be functionalized in such a way that an aromatic product can be formed when cyclization takes place. It is more common with analogous aliphatic diamine derivatives for reduced imidazoles to be formed, but there are a number of synthetically useful processes which cyclize monoacylated alkylenediamines. One example involves niono-acylated diaminomaleonitrile (see below), which can be dehydrated to form imidazoles fl5]. 

Such substrates as a-(acylamino)enaminones (4) can be made by catalytic reduction of acylated 4-aminoisoxazoles (3) [16, 17J, or acetamidines made from 4-amino-5(4/f)-isoxazolones [18]. Although the starting materials require multistep syntheses, they are quite readily available in high yields, and their reduction and transformation into imidazoles are often quantitative (see Section 6.1.2(e)). 

4(5)-Acylimidazoles are sometimes available by photochemical rearrangement of the 1-acyl isomers [19], by oxidation of suitable alcohol side chains (see Section 8.5), and by other ring-synthetic methods [20-231, although 

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