Aminocatalyzed Synthesis of Enantioenriched Phenalene Skeletons through a Friedel–Crafts/Cyclization Strategy

Abstract

A series of enantioenriched phenalene-derived compounds were accessed by a Friedel-Crafts/cyclization strategy. Starting from α,β-unsaturated aldehydes and 2-naphthol derivatives, high levels of enantioselectivity were obtained through iminium-enamine catalysis. The catalytic system composed of a diphenylprolinol silyl ether organocatalyst and triethylamine as a base was applied to a combination of diversely functionalized substrates. The obtained phenalene-derived architectures are promising building blocks for reaching natural products and exhibit fluorescence properties.

Unusual Oxidative Dealkylation Strategy toward Functionalized Phenalenones as Singlet Oxygen Photosensitizers and Photophysical Studies

“…The compound was purified by column chromatography on silica gel (6/4 PE/EtOAc). All the physical and spectroscopic data were in complete agreement with the reported ones 22. 4,9-dihydroxy-1-(3-methoxyphenyl)-1H-phenalene-2-carbaldehyde 3d.…”

“…The compound was purified by column chromatography on silica gel (7/3 PE/EtOAc). All the physical and spectroscopic data were in complete agreement with the reported ones 22. dihydroxy-1-naphthtaldehyde (1.16 mmol, 218 mg), catalyst (0.23 mmol, 75 mg), (E)-3-(4bromophenyl)acrylaldehyde (2.32 mmol, 490 mg), and Et 3 N (58 µmol, 8 µL) 22.…”

“…This procedure is based on a slightly modified experimental protocol previously reported by our group. 22 The yields were improved by simply switching the solvent from toluene to ethyl acetate. Under these conditions, the products 3 were obtained in good-to-high yields regardless of the substituents.…”

“…4,9-dihydroxy-1-(3-methoxyphenyl)-1H-phenalene-2-carbaldehyde 3d. According to the described general procedure, 810 mg (85%) of 3d (red solid) was obtained from 2,7dihydroxy-1-naphthtaldehyde (2.65 mmol, 500 mg), catalyst (0.53 mmol, 173 mg), (E)-3-(3methoxyphenyl)acrylaldehyde (5.3 mmol, 860 mg), and Et 3 N (0.13 mmol, 18 µL) 22. 1-(4-fluorophenyl)-4,9-dihydroxy-1H-phenalene-2-carbaldehyde 3f.…”

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF3·OEt2 catalysis

“…As a result of its broad scope of applications in inter/intraorganic molecular transformations, researchers are interested in creating novel, mild and efficient Friedel–Crafts methodologies. In spite of its worthwhile synthetic applications the Friedel–Crafts (FC) reaction faces a shortcoming and major challenge in operating with electron-deficient arenes [ 4 – 7 ]. Operating FC reactions in versatile synthons such as Morita–Baylis–Hillman (MBH) adducts is a challenging process.…”