Metal Salt Mediated Radical Reactions of 2‐Substituted‐1,4‐Naphthoquinones

Abstract

Metal Salt Mediated Radical Reactions of 2-Substituted-1,4-naphthoquinones.-Silver-catalyzed reaction of hydroxymethyl-substituted naphthoquinones (I) with -oxocarboxylic acids (II) provides access towards naphtho-fused furan derivatives (III). In a similar manner, aminomethyl-substituted naphthoquinones (IV) afford naphtho-fused pyrroles (V). Interestingly, manganese-mediated reaction of naphthoquinones (IV) with -keto ester (VI) gives the same naphtho-fused pyrroles (V) instead of the expected naphtho-fused pyridine derivatives. -(LIN, Z.-Y.; CHEN, Y.-L.; LEE, C.-S.; CHUANG*, C.-P.; Eur.

A Mild and Versatile Friedel–Crafts Methodology for the Diversity‐Oriented Synthesis of Redox‐Active 3‐Benzoylmenadiones with Tunable Redox Potentials

“…A first straightforward pathway to synthesize 3‐benzoylmenadiones 1 was investigated by using a silver(I)‐catalyzed decarboxylation reaction between menadione and α‐ketoaromatic acids 5 according to the reaction shown in Scheme . To do so, starting α‐keto acids 5 a and 5 a′ had to be prepared, first, by a described method and were obtained in 80 and 98 % yield, respectively.…”

“…The resulting benzylr adicals pecifically undergoes an ucleophilic radical addition to the menadione core at the C-3 position, generating the corresponding3-benzylmenadione.I nthe next step, 3-benzoylmenadiones 1 were produced by benzylic oxidation by using the CrO 3 /H 5 IO 6 reagent system. [6] Af irst straightforwardp athway to synthesize 3-benzoylmenadiones 1 was investigated by using as ilver(I)-catalyzed decarboxylation reaction [31] between menadione and a-ketoaromatic acids 5 according to the reaction shown in Scheme 2. To do so, starting a-keto acids 5a and 5a' had to be prepared, first, by ad escribed method [32] and were obtained in 80 and 98 %y ield, respectively.W hen the Kochi-Anderson reaction conditions were appliedt om enadione and a-ketoaromatic acids 5,a na cyl radicalw as generated, producing directly the 3-benzoylmenadioned erivatives 1a and 1a' in 45 %a nd 41 % yield, respectively (Scheme 2).…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…The reaction gives reasonable yields with variety of aliphatic ketoacids 3-303 , whereas aromatic ketoacids proved to be less eficient. 234c …”

Total synthesis of monosporascone and dihydromonosporascone

“…The NMR spectra of the synthetic product were virtually identical with those reported for the naturally-derived material. 15 As proof of concept that monosporascone can be a synthetic precursor to the related natural products depicted in Scheme 1, 4 was subjected to reduction with zinc in acetic acid, 39 providing dihydromonosporascone (5) in modest (but unoptimised) yield. The 1 H NMR spectrum of this material also matched the data reported for the natural product.…”