[Studies on the synthesis of analgesics. LIV. Syntheses of 3-(substituted phenyl)-4-oxazolidinone and 3-(substituted phenyl)-3,4,5,6-tetrahydro-2H-1,3-oxazin-4-one derivatives as analgesics (studies on the syntheses of heterocyclic compounds. CMXXVII) (author's transl)].