AhsbPet: Dimerization products and oxaznles have been synthesized from 4-acylaminomethyl-l-~lpy~~um salts by heating with acetic anhydride at 100°C and 140°C respectively. One explanatiw is the formation of an aahydmhase as an intwmediat.z+ therefore, a new series of anhydrobase have been prepared to carry out the reaction, achieving a good synthetic prowdure to obtain 4-(4-pyridyl)oxazole.
The 4-acylaminomethylpyridine N-oxides 1 show interesting behavior in their reaction with acetic anhydride. Small differences of temperature yield very different compounds. When the reaction is carried out at lOO"C, acetoxylation in the methylene group takes place, and the compounds 2 are formed.' The acetoxy group can easily undergo nucleophilic substitution yielding 3 when there is a nucleophile in the reaction medium.* This reaction provides a good procedure for preparation of compounds of structure 3. However, when the reaction is performed at 140°C the main products are the dimers 4 (Scheme l).s
The experimental fmdings described above with the IV-oxides, led us to study the behavior of pyridiium salts 5. We have found that oxaxoles 7 or dimeric products* 6 are formed in the reaction.
In this paper we report the resuhs obtained, Additionally, we describe a new procedure to obtain trisubstituted oxazoles with a 4-pyridyl group in 4 position 12 from the anhydrobases 14.