Potassium Phosphate

Directed γ-C(sp3)–H Alkylation of Carboxylic Acid Derivatives through Visible Light Photoredox Catalysis

“…A possible mechanistic pathway is shown in Figure . Deprotonation of 1a (p K a ≈ 11.0 in H 2 O, p K a ≈ 16.5 in DMSO) with K 3 PO 4 (p K a ≈ 12.4 in H 2 O) provides potassium amide I . A Stern–Volmer experiment (see SI for details) reveals the feasibility of single-electron oxidation of I ( E 1/2 red = +1.04 V vs saturated calomel electrode (SCE) in DMF) by the excited state of Ir­[(dF-CF 3 )­ppy] 2 ­(dtbbpy)]­PF 6 ( E 1/2 red [*Ir III /Ir II ] = +1.21 V vs SCE in MeCN), which furnishes amidyl radical II .…”

Recent Advances in Photoredox‐Mediated Radical Conjugate Addition Reactions: An Expanding Toolkit for the Giese Reaction

“…Importantly,this investigation demonstrates that, for the first time,astrong NÀH bond of an amide (BDFE % 107-110 kcal mol À1 ), [158,159] could be homolyzed in the presence of as trongly oxidizing photocatalyst and aw eak hydrogen-bonding phosphate base.W ith this base,deprotonation of an electron-rich benzamide (DpK a % 20 in MeCN) is not kinetically competitive with the luminescence decay of the excited state iridium catalyst. [160] Thus,i ti sp roposed that the hydrogen-bonding interaction between the phosphate base and the benzamide sufficiently weakens the NÀHbond, making it susceptible to oxidation in the presence of as trong Ir oxidant (Scheme 39 A). This proton-coupled electron transfer (PCET) process provides mild conditions for homolytic N À Hb ond activation, and enables previously infeasible transformations.…”