Synthesis of 6-Alkoxy-3-aryl-6-trimethylsilyloxy-5,6-dihydro-4H-1,2- oxazines and Their Acid-Catalyzed Hydrolysis Leading to 3-Aryl-5,6- dihydro-4H-1,2-oxazin-6-ones and/or 4-Aryl-4-(hydroxyimino)butyric Acid Esters.