Base-Promoted Divergent Annulation of Conjugated Ynones and Methyl 2-(Cyanomethyl)benzoates to Access 1-Naphthols and Xanthones

Abstract

A facile and efficient base-mediated divergent annulation of methyl 2-(cyanomethyl)­benzoates and conjugated ynones has been described. A broad range of 1-naphthols and xanthones were formed in moderate to excellent yields. The notable features of this protocol include readily available precursors, broad substrate scope, complete regioselectivity, and substrate-controlled divergent synthesis. The gram-scale preparation and synthetic transformations of the resulting 1-naphthols and xanthones demonstrate their utility.

A deconstruction–reconstruction strategy to access 1-naphthol derivatives: application to the synthesis of aristolactam scaffolds

“…11 Later, this approach was further modified by Wang. 12 In 1993, Furukawa developed a method using dimethyl phthalide-3-phosphonates with various Michael acceptors, which led to the formation of naphthalene-1,4-diols. 13 Recently, Mal et al reported an annulation method based on the Michael–Dieckmann cascade reaction, in which the use of simple phthalides and acrylates afforded diversely substituted 1-naphthols.…”

Transition-Metal-Free Synthesis of 3-Acyl Chromones by the Tandem Reaction of Ynones and Methyl Salicylates

“…However, they need high temperature and oxidants or electrocatalysis. Inspired by our continuous interest in ynones chemistry, we envisioned that 3-acyl chromones may be conveniently synthesized from ynones with easily available methyl salicylates through a tandem [2 + 4] cyclization reaction under transition-metal-free conditions (Scheme c). Herein, we reported a simple and efficient route to synthesize 3-acyl chromones from ynones and methyl salicylates with high regioselectivity, broad substrate tolerance, and under mild and transition-metal-free conditions.…”

NHC-Catalyzed Formal [4 + 2] Annulation of o-Formyl-Tethered Michael Acceptors and Ynones to Access Highly Functionalized Naphthalene Derivatives

“…Based on the literature precedents ,, and control experiments, a plausible mechanism is depicted in Scheme for the reaction of 1a and 2a to give 3a via NHC-catalyzed intermolecular Stetter reaction–cyclization followed by aromatization. Carbene is generated by abstraction of a proton from NHC precatalyst B .…”

“…The carbene adds to the aldehyde functionality of o -formylcinnamate 1a to give a tetrahedral intermediate I , which leads to the generation of Breslow intermediate II via 1,2 proton shift. Subsequently, the Breslow intermediate II undergoes an intermolecular conjugate addition to the β-position of ynone 2a to form an allene-type intermediate III . The enol moiety of the intermediate III undergoes intramolecular Michael addition to the α,β-unsaturated ester moiety (Michael acceptor) to form a cyclized intermediate IV with concomitant regeneration of the NHC.…”