Conversion of isatoic anhydride to o‐amino‐N(1,1‐disubstituted‐propynyl)benzamides 3a‐c followed by reflux in ethanolic potassium hydroxide gave 2‐(o‐aminophenyl)‐4,4‐disubstituted‐5‐methylene‐4H‐oxazoles 4a‐c. The treatment of same 3a‐c with triphosgene in pyridine with subsequent reflux gave 4a‐c and 2‐methylene‐3,3‐disubstituted‐oxazolo[2,3‐b]quinazolin‐5(3H)‐ones 5a‐c.
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Reisch et al. (1989) studied this question.
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