Methyl 5-phenyloxazole-4-carboxylate

A mixture of methyl isocyanoacetate (14 1.84 mL, 20 mmol), benzoyl chloride (2.15 mL, 20 mmol), and triethylamine (8.4 mL, 60 mmol) in THF (30 mL) was stirred at ambient temperature for 48 h. The reaction mixture was then concentrated in vacuo, and the residue was partitioned between water and ethyl acetate. The organic layer was separated, dried over magnesium sulfate, filtered, and concentrated in vacuo. The concentrate was triturated with -hexane and collected by vacuum filtration. Recrystallization from methanol subsequently fiimished methyl 5-phenyloxazole-4-carboxylate (18 3.70 g, 18.2 mmol, 91% yield). 

The methyl ester of 2-phenyloxazole-4-carboxylate gives the 5-methyl-derivative when methylated with lead tetraacetate. ... 

Treatment of N-benzoyl-L-alanine with oxalyl chloride, followed by methanolic triethylamine, yields methyl 4-methyl-2-phenyloxazole-5-carboxylate 32 <95CC2335>. a-Keto imidoyl chlorides, obtained from acyl chlorides and ethyl isocyanoacetate, cyclise to 5-ethoxyoxazoles by the action of triethylamine (e.g.. Scheme 8) <96SC1149>. The azetidinone 33 is converted into the oxazole 34 when heated with sodium azide and titanium chloride in acetonitrile <95JHC1409>. Another unusual reaction is the cyclisation of compound 35 to the oxazole 36 on sequential treatment with trifluoroacetic anhydride and methanol <95JFC(75)221>. 

Methoxycarbonyl)-4,6-dinitrophenyl]-2-(4-methoxyphenyl)-4-phenyloxazol-5(4//)-one affords methyl 2-(4-methoxyphenyl)-7-nitro-4-phenylquinazoline-5-carboxylate (33%) on reflux in methanol in the presence of a catalytic amount of p-toluenesulfonic acid. ... 

---