In this article, a Lewisacidmediated 1,4-addition/formal [3+2] cycloaddition reaction engaging functionalized β-carboline and 1,4-benzoquinone has been demonstrated. Application of this developed technology facilitated the construction of the challenging C-9′–C-15 quaternary center linkage in the dimeric indole alkaloid, haplophytine, and enabled the preparation of an advanced key intermediate en