2,5-Dipropyl-

Dipropyl-2-oxo-tetrahydro-E19a, 653 [Carbonsaure + En/ Cyclisierung(intra)]... 

Furan 3-Chlor-rram-4.5-dipropyl-tetrahydro- E19a, 658 (Carbon-saure + En/Lacton-Bildung)... 

Cyan-4,5-dipropyl-2-oxo-tetrahy-dro- E19a, 659 (Carbonsaure + En/Lacton-Bildung) 3-Cyan-5-hexyl-2-oxo-tetrahydro-E5, 720f./E19a, 659/664 (1-En + NC-CH2-COOH)... 

Unlike formamidine, acetamidine and benzamidine react with both aromatic and aliphatic a-hydroxyketones to give imidazoles exclusively. It has been suggested that aryl groups favour the enolic form (2) of the tautomeric mixture, resulting in the formation of oxazoles as major products. Aliphatic groups favour the keto form (1), from which imidazoles are derived. That amidines more complex than formamidine favour imidazole formation may be a consequence of steric hindrance to reaction of the enolic hydroxy groups with the amidine carbon in (2). The general reaction has been used to prepare such compounds as 4,5-dipropyl imidazole (25% yield from tris(formylamino)-methane and 5-hydroxyoctan-4-one), and a variety of 2-imidazolones and 2-aminoimidazoles [8]. The fact that oxazoles can be converted into imidazoles with some ease extends the applicability of this reaction. 

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