The selective transannular ring transformations in azirino-fused eight-membered O,N- or S,N-heterocycles was investigated. The treatment of chlorofluoro-substituted azirinobenzoxazocine initially with anhydrous zinc chloride in methylene chlorine and then with a primary amine in DMSO gave the pyridol[3,2-b][1,4]benzoxacine, and similarly, pyridol[3,2-b][1,4]benzothiazine was obtained from azirinobenzothiazocine. In stong protic acid ring opening of the protonated aziridine occured bytransannular nucleophillic O or S atom. The results show transannular ring transformation in aziro-fused eight-membered O,N- or S,N-hetrocycles involving selective aziridine ring opening and medium size contractions.