Nitrone

General structure of a nitrone

A nitrone is the N-oxide of an imine and a functional group in organic chemistry. The general structure is R₁R₂C=NR₃⁺O^- where R₃ is different from H.

A nitrone is 1,3-dipole in 1,3-dipolar cycloadditions. It reacts with alkenes to form an isoxazolidine:

One example of this reaction type is the reaction of various Baylis-Hillman adducts with C-Phenyl-N-methylnitrone forming an isoxazolidine in which R₁ is phenyl, R₂ is hydrogen and R₃ is a methyl group ^[1].

Nitrones react with terminal alkynes and a copper salt to beta-lactam. This reaction is also called The Kinugasa reaction ^[2] for example in this reaction:^[3]:

The first step in this reaction is a dipolar cycloaddition of the nitrone with the in situ generated copper(I) acetylide to a 5-membered ring structure which rearranges in the second step.

References

1. ^ Diastereoselectivity of Nitrone 1,3-Dipolar Cycloaddition to Baylis-Hillman Adducts Branislav Dugovič, Lubor Fišera, Christian Hametner and Nada Prónayovác. Arkivoc 2004 BS-834A Article
2. ^ The reactions of copper(I) phenylacetylide with nitrones Manabu Kinugasa and Shizunobu Hashimoto J. Chem. Soc., Chem. Commun., 1972, 466 - 467, doi:10.1039/C39720000466
3. ^ A novel synthesis of -lactam fused cyclic enediynes by intramolecular Kinugasa reaction Runa Pal and Amit Basak Chem. Commun., 2006, 2992 - 2994, doi:10.1039/b605743h