Photoredox-catalyzed decarboxylative alkylation/cyclization of alkynylphosphine oxides: a metal- and oxidant-free method for accessing benzo[b]phosphole oxides

Abstract

By photoredox-catalysis, alkylation/aryl cyclization of alkynylphosphine oxides towards benzo[b]phospholes has been realized under metal- and oxidant-free conditions at room temperature.

Photoredox-catalyzed stereoselective alkylation of enamides with N-hydroxyphthalimide esters via decarboxylative cross-coupling reactions

“…Recent advances in this arena have witnessed a rapid development in a broad range of decarboxylative cross-coupling reactions to forge C(sp 3 )–C or C(sp 3 )–X (X = Si, B, Se, etc. ) bonds via transition-metal14,15 and photoredox catalysis,16,17 as elegantly established by the groups of Baran,14a–g,o,15b Weix,14h,i Fu,16c–g,17a,b Oestreich,15 Phipps,16 a Xiao,16 l and many others 18. Very recently, Fu and co-workers demonstrated a brand new catalytic combination of sodium iodide and triphenylphosphine for the cross-coupling of redox-active esters with silyl enol ethers or heteroarenes without resorting to the use of dye or transition-metal based photocatalysts 19.…”

Visible Light‐Induced Regioselective Decarboxylative Alkylation of the C(sp2)−H Bonds of Non‐Aromatic Heterocycles

“…Visible light‐induced photoredox catalysis has become a powerful tool for discovering and improving selective chemical transformations using mild reaction conditions and low‐energy irradiation . Recently, we developed a photoredox‐catalysed decarboxylative alkylation/cyclization of alkynylphosphine oxides, where alkyl radical rearrangement products were not observed . Enlightened by this result, we envisioned that regioselective decarboxylative alkylation of non‐aromatic heterocycles could be achieved by carefully tuning the reaction parameters.…”

“…We commenced our studies by choosing coumarin 1 a as a starting substrate. Upon treatment of coumarin 1 a and cyclohexyl N ‐hydroxyphthalimide esters (NHPI esters) 2 a in the presence of 0.2 mol% Ru(bpy) 3 Cl 2 ⋅ 6H 2 O, DIPEA ( N , N ‐diisopropylethylamine) in 2.0 mL of DMAc ( N , N ‐dimethylacetamide) at room temperature under direct sunlight for 2.0 h, the desired decarboxylative alkylation product 3‐cyclohexyl‐2 H ‐chromen‐2‐one ( 3 aa ) was obtained in 29% GC yield (Table , entry 1). Based on the result, the reaction parameters were investigated.…”

“…[15] Recently, we developed a photoredox-catalysed decarboxylative alkylation/cyclization of alkynylphosphine oxides, where alkyl radical rearrangement products were not observed. [16] Enlightened by this result, we envisioned that regioselective decarboxylative alkylation of nonaromatic heterocycles could be achieved by carefully tuning the reaction parameters.…”

Generation of Alkyl Radicals: From the Tyranny of Tin to the Photon Democracy

“… 350 Moreover, the same radical precursors have been used for the derivatization of alkynylphosphine oxides under metal- and oxidant-free conditions to form benzo[ b ]phospholes in very good yields. 351 …”