Isochromans, isothiochromans and tetrahydroisoquinolines (THIQ) are simple core structures commonly found in natural products and bioactive compounds; for example they constitute the cores of a 5-HT1D receptor agonist, 1 cancer chemopreventive compounds and aminopeptidase inhibitors (Error! Not a valid bookmark self-reference.). Traditionally, these motifs are formed via the Pictet-Spengler (PS) reaction and variants, the oxa-Pictet-Spengler (OPS) and thia-Pictet-Spengler (TPS) reactions. A key requirement of these reactions, including recently-reported asymmetric versions of the PS and OPS reactions, is that the β-aryl ring of the nucleophile is electron-rich. This requirement severely limits the scope of possible products that can be easily synthesized, which prompted us to seek alternatives. An alternative that has been explored is to functionalize the 1position of a pre-existing core (Figure ). Recently, several syntheses of 1-substituted isochromans and THIQ cores through oxidation to oxocarbenium and iminium ions respectively, followed by nucleophilic addition have been reported. Jacobsen and co-workers generated similar intermediates through thiourea-catalyzed formation of oxocarbenium ions from 1-chloroisochromans (Figure ), followed by an enantioselective nucleophilic addi-tion. Smith and co-workers generated tetrahydroisoquinoline-derived iminium ions photocatalytically using CCl3Br as oxidant followed by addition of an enolate (Figure ). Similarly, Seidel and co-workers developed an α-C-H functionalization sequence via deprotonation of the N-H, followed by hydride transfer to generate a reactive imine that was arylated by an aryl lithium reagent (Figure ). Analogous reactions involving isothiochromans are exceptionally rare. In contrast to the focus on oxocarbenium and iminium ions in the functionalization of isochroman and THIQ compounds, reaction development involving a long-lived 1-isochroman or THIQ radical (intermediate, Figure ) remains underexplored. Recently, carboxylic acids have been used as precursors to carbon-centered radicals using photoredox catalysis. MacMillan and Doyle developed a nickel metallaphotoredox catalyzed decarboxylative arylation using carboxylic acids and aryl halides. This was expanded to achieve the coupling of carboxylic acids and alkyl halides in the first metallaphotoredox-catalyzed sp 3 -sp 3 coupling. We hoped to generate the corresponding 1-iso(thio)chroman and THIQ radicals in a controlled manner to access a range of 1-substituted cores from their carboxylic acid building blocks, particularly those with electron-withdrawing functionality on the aromatic rings.