Photocatalytic Markovnikov-Selective Sulfonation of Alkynes for Indoline Synthesis.

The indoline scaffold, a privileged class of nitrogen-containing heterocycles, is ubiquitous in bioactive natural products and pharmaceuticals; consequently, the development of efficient synthetic strategies remains a forefront of organic synthesis. Herein, we report a visible-light-induced Markovnikov-selective sulfonylation/cyclization cascade, enabling the mild and efficient construction of 3-sulfonyl indolines from o-aminoarylalkynes and sodium sulfinates. Mechanistic studies reveal that the transformation proceeds via a radical-mediated pathway, initiated through either an electron donor-acceptor (EDA) complex or a photocatalytic cycle, wherein sodium sulfinate serves as a pivotal electron donor. This work provides a green and atom-economical strategy for the modular synthesis of functionalized indolines.