In order to examine the effect of bulky substituents on ring fission, benzyl 4-R
1-5-R
2-2-oxazolecarbamate (I) and 2-amino-4-R
1-5-R
2-oxazole (II) were submitted to catalytic reduction. I was converted to II when using palladium-carbon-B in ethanol. Excepting 5-alkyl-I and 4-tert-butyl-5-phenyl-I (In), I afforded 1-R
1-2-R
2-ethylurea (III) when using palladium-carbon-A catalyst in ethanol. When using platinum oxide in acetic acid, 5-methyl (Id) and aralkyl-I were converted to 1-benzyloxycarbonyl-3-(1-R
1-2-R
2-ethyl) urea (IV), 5-ethyl (Ie) and 5-isopropyl (If) afforded a mixture of III and IV, and 5-tert-butyl (Ig) and alkyl, aryl disubstituted I, excepting In, gave III. The bulky substituents present in the oxazole ring was found to give some marked effect on ring fission.
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