Periselectivity in the aza-Diels–Alder Cycloaddition between α-Oxoketenes and N -(5-Pyrazolyl)imines: A Combined Experimental and Theoretical Study - MédiHAL Accéder directement au contenu
Image (Illustration) Année : 2020

Periselectivity in the aza-Diels–Alder Cycloaddition between α-Oxoketenes and N -(5-Pyrazolyl)imines: A Combined Experimental and Theoretical Study

Résumé

The thermal 6π aza-Diels−Alder cycloadditions between α-oxoketenes, in situ derived from a thermally induced Wolff rearrangement of 2-diazo-1,3-diketones, and N-(5-pyrazolyl)imines as prototypical electron-rich 2-azadienes lead to two distinct sets of products, essentially as a function of the nature of the α-oxoketenes involved. For instance, cyclic five-membered α-oxoketenes lead preferentially to spiro hydropyridin-4-ones, which involves the α-oxoketenes as the 2π partners at their C=C double bond and the N-(5-pyrazolyl)imines as the 4π partners at their 2-azadiene moiety. In contrast, other cyclic and acyclic α-oxoketenes lead preferentially to 1,3-oxazin-4-ones, which now involves the α-oxoketenes as the 4π partners at their 1-oxadiene moiety and the N-(5- pyrazolyl)imines as the 2π partners at their C=N double bond. A computational modeling study using DFT methods allowed rationalizing this change of periselectivity: the formation of spiro hydropyridin-4-ones is under thermodynamic control while the formation of 1,3-oxazin-4-ones is kinetically controlled, and slightly thermodynamically disfavored in the five-membered ring series. The competing cyclodimerization of the α-oxoketenes is also studied in detail.

Domaines

Chimie organique

Dates et versions

hal-02990549 , version 1 (05-11-2020)

Licence

Domaine public

Identifiants

  • HAL Id : hal-02990549 , version 1

Citer

Juan-Carlos Castillo, Brian Castro Agudelo, Jaime Gálvez, Yannick Carissan, Jean Rodriguez, et al.. Periselectivity in the aza-Diels–Alder Cycloaddition between α-Oxoketenes and N -(5-Pyrazolyl)imines: A Combined Experimental and Theoretical Study. Illustration. France. 2020. ⟨hal-02990549⟩
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