2-benzyloxy-5 -oxazolones

Oxidative dimerization of various 2-benzyloxy-2-thiazoline-5-ones (222) catalyzed by iodine and triethylamine is another example of the nucleophilic reactivity of the C-4 atom (469) (Scheme 112). Treatment of 212 with pyrrolidinocyclohexene yields the amide (223) (Scheme 113). The mechanism given for the formation of 223 is proposed by analogy with the reactivitx of oxazolones with enamines (4701. 4-Substituted 2-phenylthiazol-5(4Hi-ones react with A -morphoiino-l-cyclohexene in a similar manner (562j. Recently. Barret and Walker have studied the Michael addition products... 

The UV irradiation of the 2-allyloxy-4,5-diphenyloxazole 41 results in the predominant formation of 5-substituted-2(5/T)-oxazolones 44, in contrast to the thermal aza-Claisen rearrangement which readily affords the 2(3/T)-oxazolones 42. The photolysis proceeds via allyl-O bond scission with the generation of a radical pair that subsequently recombines to produce 5-substituted-2(5/T)-oxazolones. Similar results were obtained with 2-(benzyloxy)-4,5-diphenyloxazole (Fig. 5.75). °... 

Benzyloxy-4-isopropyl(or 4-terf-butyl)-4-methyl-5(4//)-oxazolones 780 have been prepared from an A-benzyloxycarbonylamino acid 779 using l-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide hydrochloride (EDAC HCl) as the cyclization agent (Scheme 7.237). Treatment of 780 with tetramethylfiuoroformamidinium hexafiuorophosphate (TFFH) has shown that they are possible intermediates in the fluorination of a-methyl-a-alkyl amino acids by TFFH. 

Three groups have reported on the conversion of the Af-benzyloxy-carbonyl derivatives of 2-amino-2-deoxy-D-glucose (162) and (163) to the oxazolones (166) and (167), respectively. Zervas and coworkers used... 

Herdeis and Gebhard prepared 2-amino-4-(5-benzyloxy-2-pyridyl)-5-hy-droxyoxazole 576 as part of their on-going studies of heterocyclic amino acids (Scheme 1.157). They reported that the Bucherer-Bergs reaction of 5-benzyloxy-2-pyridinecarboxaldehyde with KCN, ammonium chloride, and ammonium carbonate in refluxing aqueous ethanol gave 576 as the sole product. The structure of 576 was confirmed by hydrolysis to 5-hydroxy-2-pyridylglycine 577. Most likely, 576 exists as the 5(4//)-oxazolone tautomer (see Chapter 7). 

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