Metal-free synthesis of difluoro/trifluoromethyl carbinol-containing chromones via tandem cyclization of o-hydroxyaryl enaminones

Abstract

A convenient and efficient method for the synthesis of difluoro/trifluoromethyl carbinol-containing chromone derivatives has been developed.

Total Synthesis of Alanense A through an Intramolecular Friedel–Crafts Alkylation

“…Toluene and THF led to the formation of a complex mixture of products (entries 8 and 9, respectively). No reaction occurred in the absence of p -TsOH·H 2 O in HFIP (entry 10), indicating HFIP itself does not have enough power to promote the cyclization . Interestingly, HFIP made it possible to reduce the amount of Lewis acid promoter such as FeCl 3 to a catalytic amount, but it requires strict anhydrous conditions to obtain a high product yield (entry 11).…”

Electrochemical-induced solvent-tuned selective C(sp3)–H bond activation towards the synthesis of C3-functionalized chromone derivatives

“…Enaminones have lately been known as utility and valuable reaction intermediates owing to the ambident nucleophilic and electrophilic characteristics of the enamine and enone groups, respectively, which were exploited by many synthetic chemists towards the synthesis of various biologically important heterocycles, such as some C3-functionalized chromones. 14–20 In particular, Yang and coworker reported the metal-free synthesis of difluoro/trifluoromethyl carbinol-containing chromones using o -hydroxyaryl enaminones as reaction substrates. 20 At the same time, photoredox catalysis and enzyme catalysis are also utilized to synthesize C3-functionalized chromones via the activation of the C(sp 3 )–H bond (Scheme 1).…”

“…14–20 In particular, Yang and coworker reported the metal-free synthesis of difluoro/trifluoromethyl carbinol-containing chromones using o -hydroxyaryl enaminones as reaction substrates. 20 At the same time, photoredox catalysis and enzyme catalysis are also utilized to synthesize C3-functionalized chromones via the activation of the C(sp 3 )–H bond (Scheme 1). 21–23 Interestingly, Zhou's group reported the synthesis of 3-arylthiochromones via electrochemical tandem cyclization of o -hydroxyaryl enaminones.…”