Reactions of 1-Naphthols with .PI.-Acceptor p-Benzoquinones: Oxidative Aryl Coupling vs. Non-Oxidative Electrophilic Arylation

Abstract

We investigated the reactions of various 1-naphthols (NPOHs; 1) with p-benzoquinones (Qs), such as 1,4-benzoquinone (BQ) and p-chloranil (CA), as p p-electron acceptors. With electron-rich NPOHs 1a-c, oxidative biaryl coupling and subsequent dehydrogenation reaction took place selectively to give the corresponding 2,2Ј-binapthyl-1,1Ј-quinones 3a-c in excellent yield. In the case of electron-deficient NPOHs 1e, f, two different types of reactions occurred in the presence of SnCl 4 and ZrO 2 under similar conditions: SnCl 4 mediated oxidative dimerization and trimerization of NPOH, while ZrO 2 promoted electrophilic arylation of Qs with NPOH. The resulting products 3 would be useful synthetic intermediates for naturally occurring diosindigo B, biramentaceone and violet-quinone.

Visible‐Light‐Promoted Dearomative Fluoroalkylation of β‐Naphthols through Intermolecular Charge Transfer

“…Based on these investigations and previous reports, we propose a radical chain propagation pathway (Figure ). First, in the presence of Cs 2 CO 3 , β‐naphthol is deprotonated to give the β‐naphtholate anion A .…”

Visible‐Light‐Promoted Dearomative Fluoroalkylation of β‐Naphthols through Intermolecular Charge Transfer

“…[10] Recently,v isible-light-promoted cross-couplings by intermolecular charge transfer underwent adramatic development. [12] Herein, we report the first visible-light-induced dearomative fluoroalkylation of b-naphthols that relies upon the formation of an EDAcomplex and does not require the assistance of ap hotoredox catalyst. H owever,o nly very few transformations of b-naphthols that rely on the formation of EDA complexes have been disclosed.…”

Naphthol radical couplings determine structural features and enantiomeric excess of dalesconols in Daldinia eschscholzii

“…The work highlights the possibility of increasing the structural diversity of secondary metabolites through radical couplings of phenolic precursors such as polyhydroxy naphthols that have been found in many fungi 14,15 and bacteria 4 . The findings are valuable for fertilizing or rethinking the concept and/or approach for the (bio)organic syntheses of important compounds from hydroxyphenylated starter molecules 7,[26][27][28] . Furthermore, the investigation foretells as well that the laccase-catalyzed radical coupling among different starting phenols to form useful natural products of high complexity may be quite common.…”