An easy, fast, and cheap way for the synthesis of the new 4′-(4-hydroxy-3-methoxyphenyl)- 3′-methyl-3′, 4′-dihydro-1′ H-spiro [indoline-3, 2′-quinolin]-2-ones using BF3 OEt2- promoted imino Diels–Alder cycloaddition between ketimine-isatin derivatives and trans- isoeugenol.