One-pot photocatalytic transformation of indolines into 3-thiocyanate indoles with new Ir(iii) photosensitizers bearing β-carbolines

Abstract

Herein, we harness the combination of two photocatalytic reactions, promoted by new Ir(iii) photosensitizers, for the direct access to 3-thiocyanato indoles from indolines in a one-pot process.

Photocatalytic Aerobic Dehydrogenation of N-Heterocycles with Ir(III) Photosensitizers Bearing the 2(2′-Pyridyl)benzimidazole Scaffold

“…The HOMOs calculated for [1] + , [2] + , and the new derivatives are formed by a combination of Ir orbitals (d π ) and C^N orbitals (π of ppy – or dfppy – ) as described elsewhere for this type of complexes. ,, Hence, the HOMOs are located on the Ir metal center and the phenyl rings of the C^N ligands, although they exhibit a π-antibonding nature at the Ir–C phenyl interfaces. On the contrary, the LUMOs are distributed mainly over the N^N′ ligands (bpy or 2-(2′-pyridyl)­benzimidazole scaffold of L1 – L5 ) in all the cases, , with a very small contribution of the Ir d π orbitals.…”

“…In a previous work, we have designed a family of new Ir(III) biscyclometalated complexes with β-carbolines as efficient photocatalysts for the one-pot oxidative thiocyanation of indolines, which produces the respective 3-thiocyanate indoles. 20 We have also reported on a protocol to prepare α-amino nitriles through the Ru-photosensitized oxidative cyanation of amines. 21 …”

“…In a previous work, we have designed a family of new Ir(III) biscyclometalated complexes with β-carbolines as efficient photocatalysts for the one-pot oxidative thiocyanation of indolines, which produces the respective 3-thiocyanate indoles. 20 We have also reported on a protocol to prepare αamino nitriles through the Ru-photosensitized oxidative cyanation of amines. 21 In this work, we present the synthesis of new Ir(III) biscyclometalated complexes of general formula [Ir-(C^N) 2 (N^N′)]Cl, where C^N = 2-(2,4-difluorophenyl)pyridinate (dfppy) and N^N′ stands for different N,N-donor ligands containing the 2-(2′-pyridyl)benzimidazole scaffold.…”

Recent advances in photochemical and electrochemically induced thiocyanation: a greener approach for SCN-containing compound formation

“…Espino et al outlined the synthesis of innovative Ir( iii ) bis-cyclometallated photosensitizers with β-carboline ligands and a facile and unique photocatalytic one-pot two-step process for the chemoselective and C-3 regioselective oxidative thiocyanation of indolines 66 and production of 3-thiocyanatoindoles 67 in good to high yields. 29 They used ammonium thiocyanate, molecular oxygen as a green oxidant, and Ir( iii ) photocatalysts in THF at room temperature in the presence of blue light as the energy source ( Scheme 22 ).…”

Recent progress of direct thiocyanation reactions

“…In 2021, Espion's group reported a synthetic procedure for the one-pot photocatalytic transformation of indolines 153 into 3-thiocyanato indoles 154 with new Ir( iii ) photosensitizers bearing β-carbolines, 49 as shown in Scheme 42. The combination of two photocatalytic reactions in a one-pot process is interesting, and they used O 2 and light to make the reaction sustainable.…”