External-photocatalyst-free visible-light-mediated aerobic oxidation and 1,4-bisfunctionalization of N-alkyl isoquinolinium salts

Abstract

Visible light mediated aerobic alternate transformations of N-alkyl isoquinolinium/quinolinium salts in the absence of extra-added photocatalysts are reported, which provides a highly concise, sustainable and low-cost protocol to unsaturated lactams...

Iodination/Amidation of the N-Alkyl (Iso)quinolinium Salts

“…In addition, the reaction efficiency was reduced after adding an 1 O 2 scavenger, 1,3-diphenylisobenzofuran (DPBF), along with a significant amount of 1,2-dibenzoylbenzene. This observation revealed that a singlet oxygen was present in the system, which might be generated via the energy transfer between the quinolinium salts and molecular oxygen under visible-light irradiation . The fact that the yields decreased significantly in the absence of either light or oxygen further supported our assumption.…”

“…These metal-free, one-pot reactions provided promising methodology for the synthesis of N -benzyl-substituted iodo-(iso)­quinolinones. Very recently, a visible-light-promoted aerobic oxidation of N -alkyl isoquinolinium salts to synthesize 4-iodoisoquinolones in the presence of I 2 /Cs 2 CO 3 was disclosed by Song’s group . However, in case of the N -alkylquinolinium iodide salts, only oxidation products N -alkyl quinolones were obtained.…”

Synthesis of 3‐Methyleneisoindolin‐1‐ones and Isoquinolinium Salts via Exo and Endo Selective Cyclization of 2‐(1‐Alkynyl)benzaldimines

“…of iodine in DCE under air, 5 a underwent 1,4‐bisfunctionalization to give 4‐iodo‐isoquinolin‐1(2H)‐one 9 in 61 % yield [Equation (1), Scheme 9]. [2i] The dearomative trifunctionalization of isoquinolinium salt 5 a could be realized by reacting 5 a with 4‐hydroxycoumarins in the presence of triethylamine, offering an oxazatricycle product 10 with a good yield of 71 % [Equation (2), Scheme 9]. [3b] Finally, 5 h proved to be easily transformed to tetrahydroisoquinoline derivative 11 via a tandem reductive methylation‐hydroxymethylation process [Equation (3), Scheme 9].…”

A Palladium(0)‐Catalyzed C4 Site‐Selective C−H Difluoroalkylation of Isoquinolin‐1(2H)‐Ones

“…However, as a result of remote position, only a few reactions at C4 were reported [19] . When isoquinolin‐1( 2H )‐one 1 was reacted with Br 2 , I 2 , NCS, TSCF 3 , ICI, HNO 3 or NFSI respectively, different substituents (−Br, −I, −Cl, −CF 3 , −NO 2 or −F) could be introduced at C4‐position (Scheme 1a) [19a–h] . Through a radical pathway, C‐4 thiolated isoquinolin‐1( 2H )‐ones were obtained by reacting 1 with diaryl disulfides (Scheme 1b) [19i–j] .…”