A Photocatalytic Meerwein Approach to the Synthesis of Isochromanones and Isochromenones

Abstract

A visible-light RuII photoredox Meerwein synthesis of isochromanones and isochromenones is described starting from diazonium salts of differently substituted anthranilic acids

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

“…Analogous results were obtained when the substitution pattern on both the diazonium salt and the alkene was varied, results that paralleled those reported by König and Fagnoni [5]. In our hands reactions were slower (6–8 h vs 2 h), probably due to the lower loading of photocatalyst (0.5% vs 2%) and excess of alkene (2 equiv vs 3 equiv) employed; moreover, the use of an inert atmosphere did not lead to significant improvements.…”

“…Also trans -stilbene reacted under the reaction conditions, but the 3,4-disubstituted isochromanone was isolated in only 19% yield. Noteworthy, compounds 4c , 4d and 4f , whose synthesis was previously reported starting from carboxylic acids [5], were obtained with comparable yields.…”

“…While working on this project, König and Fagnoni reported the photoredox-catalyzed reaction of 2-carboxybenzenediazonium salts with various alkenes [5], which prompted us to disclose our results in this communication.…”

Visible‐Light‐Induced, Catalyst‐Free Radical Arylations of Arenes and Heteroarenes with Aryldiazonium Salts

“…Having found that radical arylation reactions with arenediazonium salts can be conducted under such simple reaction conditions, we finally evaluated whether the addition of the typical photocatalyst [Ru(bpy) 3 ]Cl 2 (2 mol %) could further improve the reaction outcome. From eight comparative experiments conducted with 4‐chlorophenyldiazonium chloride (or tetrafluoroborate) 5 a,a′ and the arenes 1 – 4 , thiophene, N ‐Boc pyrrole, 1,4‐benzoquinone, and benzene, only the two reactions to the thiophene‐ and benzoquinone‐derived biaryls 10 a and 12 a gave yields increased by 8 and 11 %, respectively, when the photocatalyst was present.…”

An Unprecedented Synthesis of 3,3‐Disubstituted Isochroman‐1,4‐diones Using Nitrones as Oxygen Atom Donors

“…The isochroman‐1‐one (isocoumarin) moiety is a widely known structural motif in a variety of natural products possessing significant biological and pharmacological activities and therefore have gained immense synthetic interest (Fig. ). Similarly, isochroman‐1,3‐diones and isochroman‐1,4‐diones are also known to have enhanced biological properties.…”