| 摘要 |
A process for preparing a compound of the formula I is disclosed, which comprises (a) to prepare a compound without a double bond in the 4,5-position of the oxazole or oxazine ring and wherein R is hydrogen or lower-alkyl of 1-3 carbon atoms cyclizing a compound of the formula wherein Hal' is chlorine or bromine, by heating the latter in an inert solvent in the presence of an acid-acceptor, excluding compounds wherein Y is an alkylene bridge interrupted by an olefinic linkage; or (b) to prepare a compound wherein X is 0, reacting a compound of the formula wherein Hal is chlorine, bromine or iodine, with an alkali metal salt of a compound of the formula , excluding compounds wherein R1 and R2 are loweralkoxycarbonyl. |
