An isomerization–ring-closing metathesis (RCM) strategy afforded N-substituted 4 H-1,4-benzoxazines from the protected N-allyl-2-(allyloxy)anilines. In addition, RCM was used to synthesize the N-substituted, 8-membered benzo-fused heterocycles from the respective diallyl compounds: 1,2,5,6-tetrahydro-1,6-benzodiazocine, 5,6-dihydro-2 H-1,6-benzoxazocine, 5,6,9,10-tetrahydropyrido[2,3- b][1,4]diazocine and 5,6-dihydro-2 H-1,6-benzothiazocine 1,1-dioxide. The isomerization–RCM approach also afforded the 7-membered ring system, 2,5-dihydro-1,5-benzothiazepine 1,1-dioxide, from the protected N-allyl-2-(allylsulfonyl)aniline. Furthermore, the structure of 1,6-bis[(4-methylphenyl)sulfonyl]-1,2,5,6-tetrahydro-1,6-benzodiazocine was confirmed by a single crystal X-ray determination.