Formal [4+2] Cycloaddition of Vinyl Benzoxazinones with Oxazol‐5‐(4 H )‐Ones for Diastereoselective Construction of 3,4‐Disubstituted Dihydro‐2(1 H )‐Quinolinones

Construction of 3,4-Dihydroquinolone Derivatives through Pd-Catalyzed [4+2] Cycloaddition of Vinyl Benzoxazinanones with α-Alkylidene Succinimides

The construction of 3,4-dihydroquinolone derivatives has attracted a considerable amount of attention due to their extensive applications in medicinal chemistry. In this study, we present the Pd-catalyzed [4+2] cycloaddition of vinyl benzoxazinanones with α-alkylidene succinimides for the efficient synthesis of 3,4-dihydroquinolones. This approach presents numerous advantages, including the ready availability of starting materials, mild reaction conditions without the use of additional bases, and a wide range of substrates. In particular, all of the desired products can be easily afforded in high yields (≤99%) and excellent diastereoselectivities (>20:1). The practicality and reliability of this strategy were demonstrated by the successful scale-up synthesis and subsequent straightforward synthetic transformations.

Facile Synthesis of Quinoline-Substituted 3-Hydroxy-2-oxindoles and 3-Amino-2-oxindoles via a Palladium-Catalyzed Cascade Intramolecular Cyclization/Intermolecular Nucleophilic Addition Reaction

An efficient cascade intramolecular cyclization/intermolecular nucleophilic addition reaction of allenyl benzoxazinone with isatin or isatin-derived ketimine has been established by using Pd0-π-Lewis base catalysis. A series of 3-hydroxy-2-oxindoles and 3-amino-2-oxindoles with quaternary carbon atoms at the C3 position were synthesized in good yields under mild conditions through this protocol.

Recent Advances in Palladium-Catalyzed [4 + n] Cycloaddition of Lactones, Benzoxazinanones, Allylic Carbonates, and Vinyloxetanes

Palladium-catalyzed allylation cyclization reaction has recently emerged as an efficient and powerful synthetic platform for the construction of diverse and valuable carbo- and heterocycles. Thus the development of new allylic motifs for achieving this type of transformations in high reactivity and selectivity is of great importance. Generally, these substrates have been utilized as 1,3-, 1,4-, 1,5-, 1,6-dipoles in many reactions, which are applied to prepare highly functionalized products with complete control of chemo-, regio-, diastereo-, and enantioselectivity. In this review, we focus our attention on the development of palladium-catalyzed [4 + n] cycloaddition of allylic motifs and describe a comprehensive and impressive advances in this area. Meanwhile, the related mechanism and the application of these annulation strategies in natural product total synthesis will be highlighted in detail.

[4 + 2] Annulation of δ-Hydroxy/δ-Sulfonamido-α,β-Unsaturated Ketones with Azlactones for Diastereoselective Synthesis of Highly Substituted 3-Amino-δ-Lactones and 3-Amino-δ-Lactams

The first base-mediated [4 + 2] annulation of δ-hydroxy-α,β-unsaturated ketones with azlactones has been developed, through which 3,4-disubstituted 3-amino-δ-lactones were obtained in good yields and with excellent diastereoselectivities. This approach was also applied to the [4 + 2] annulation of δ-sulfonamido-α,β-unsaturated ketones, which provided a practical protocol for constructing biologically important 3-amino-δ-lactam frameworks.

Synthesis of 2,3,4-trisubstituted pyrrole derivatives via [3 + 2] cyclization of activated methylene isocyanides with 4-(arylidene)-2-substituted oxazol-5(4H)-ones

An efficient base-catalyzed [3 + 2] cyclization between isocyanides and 4-(arylidene)-2-substituted oxazol-5(4H)-ones has been successfully developed to form 2,3,4-trisubstituted and 2,2,3,4-tetrasubstituted pyrrole derivatives.