Visible-Light-Promoted and Yb(OTf)₃-Catalyzed Constructions of Coumarin-Pyrrole-(Iso)quinoline-Fused Pentacycles: Synthesis of Lamellarin Core, Lamellarin D Trimethyl Ether, and Lamellarin H

Abstract

The efficient construction of a coumarin-pyrrole-isoquinoline-fused pentacycle via the visible-light-promoted cyclization of 4-(isoquinolin-1-ylmethyl)-3-nitrocoumarin or Yb(OTf)3-catalyzed coupling of 4-chloro-3-nitrocoumarin and 1-methylisoquinoline is reported. This methodology has further led to the development of the concise synthesis of the lamellarin core in one, two, and three steps, as well as of lamellarin D trimethyl ether in three steps.

Ytterbium Triflate Catalyzed Synthesis of Heterocycles

“…Two coumarin-pyrrole-isoquinoline pentacycles were prepared by the Yb(OTf) 3 -catalyzed coupling of 4-chloro-3nitro-2H-chromen-2-one and 1-substituted isoquinolines by Yang and co-workers (Scheme 148). 184 Yb(OTf) 3 was found to be best Lewis acid for this transformation among the various catalysts tested, including AlCl 3 , FeCl 3 , NiNO 3 , BF 3 •OEt 2 , Sc(OTf) 3 , Ga(OTf) 3 , and Bi(OTf) 3 . The reaction of 4chloro-3-nitro-2H-chromen-2-one with 1-methylisoquinoline in the presence of 10 mol% Yb(OTf) 3 gave 54% yield of 6a,14a-dihydro-6H-chromeno[4′,3′:4,5]pyrrolo[2,1-a]isoquinolin-6-one.…”

Visible Light‐Induced Synthesis of Functionalized Coumarins

“…[86] In this context, in 2016, a visible light-induced synthesis of coumarinpyrrole-isoquinoline-fused pentacycles 176 was achieved by Yang's group (Scheme 48). [87] In this strategy, first, 4-(isoquinolin-1-ylmethyl)-3-nitrocoumarin 175 was synthesized from 4-chloro-3-nitrocoumarin 173 with 1-methylisoquinoline 174, which upon visible light irradiation gave the final product with excellent yields. It is proposed that under the visible The π-expanded coumarins have been used in different research areas owing to their wide spread applications in materials such as laser dyes, liquid crystal materials, fluorescent probes etc.…”

Multicomponent Reactions of Arylglyoxal, 4‐Hydroxycoumarin, and Cyclic 1,3‐C,N‐Binucleophiles: Binucleophile‐Directed Synthesis of Fused Five‐ and Six‐Membered N‐Heterocycles

“…[14][15][16][17] In particular, coumarin-fused pyrroles and dihydropyridines have wide applications in medicinal chemistry. [18][19][20][21][22] Apart from clinical applications they also exhibit other properties, such as photochemistry and redoxswitching, [23] NIR fluorescent BODIPY dyes with large Stokes shifts, [24] chromophores with intramolecular charge transfer character, [25] fluorescent molecules with high quantum yields, [26,27] and so on. Similar to coumarin-fused N-heterocycles, pyrimido-pyrroles (pyrroles fused with pyrimidines) are also a very important class of molecules, and considerable attention has been paid in recent times either to the develop-fused pyrroles.…”

“…Fused pyrroles and dihydropyridines/pyridines are ubiquitous in natural products as well as in many synthetic pharmaceuticals . In particular, coumarin‐fused pyrroles and dihydropyridines have wide applications in medicinal chemistry . Apart from clinical applications they also exhibit other properties, such as photochemistry and redox‐switching, NIR fluorescent BODIPY dyes with large Stokes shifts, chromophores with intramolecular charge transfer character, fluorescent molecules with high quantum yields,, and so on.…”