A domino approach for the synthesis of naphtho[2,1-b]furan-2(1H)-ones from azlactones

Multicomponent Synthesis of Diversified Chromeno[3,2-d]oxazoles

A practical and efficient synthetic procedure to novel chromeno[3,2-d]oxazoles through a one-pot sequential multistep process is presented. This procedure proceeds efficiently in propylene carbonate (PC) as a green solvent and affords a wide range of the chromenooxazole scaffolds.

Organocatalytic Aza-Friedel-Crafts/Lactonization Domino Reaction of Naphthols and Phenols with 2-Acetamidoacrylate to Naphtho- and Benzofuranones Bearing a Quaternary Center at the C3 Position

N-Acetyl ketimine generated from methyl 2-acetamidoacrylate was explored to develop an unprecedented domino aza-Friedel-Crafts/lactonization reaction with naphthols and phenols (including 5-hydroxyindoles). This novel method requires a catalyst loading of only 5 mol % of a phosphoric acid catalyst and provides a new series of 3-NHAc-naphtho- and benzofuranone derivatives bearing tetra-substituted stereogenic centers in moderate-to-good yields. The enantioselective variant using BINOL-derived phosphoric acids was also explored with 1-naphthol, providing the desired product with moderate enantioselectivities (up to 99:1 following recrystallization).

An efficient synthesis of naphtho[2,1-b]furan-2(1H)-ones catalysed by Nafion-H supported on silica-coated super paramagnetic iron oxide nanoparticles

A one-pot procedure is descibed for the synthesis of naphtho[2,1- b]furan-2(1 H)-ones via a multicomponent reaction of aryl aldehydes, hippuric acid, acetic anhydride and β-naphthol in the presence of Nafion-H supported on silica-coated superparamagnetic iron oxide nanoparticles under microwave irradiation. The catalyst can be recovered easily and reused several times without significant loss of catalytic activity.

Azlactone Reaction Developments

Azlactones (also known as oxazolones) are heterocycles usually employed in the stereoselective synthesis of α,α-amino acids, heterocycles and natural products. The versatility of the azlactone scaffold arises from the numerous reactive sites, allowing its application in a diversity of transformations. This review aims to cover classical and recent applications of oxazolones, especially those involving stereoselective processes. After a short introduction on their structures and intrinsic reactivities, dynamic kinetic resolution (DKR) processes as well as reactions involving stereoselective formation of a new σ C-C bond, such as alkylation/allylation/arylation, aldol, ene, Michael and Mannich reactions will be exposed. Additionally, cycloadditions, Steglich rearrangement and sulfenylation reactions will also be discussed. Recent developments of the well-known Erlenmeyer azlactones will be described. For the most examples, the proposed mechanism, activation modes and/or key reaction intermediates will be exposed to rationalize both the final product and the observed stereochemistry. Finally, this review gives an overview of the synthetic utility of oxazolones.