Azomethine Ylides, and Nitrile Imines

Microwave-induced 1,3-dipolar cydoaddition reactions involving azomethine ylides have been widely reported in the literature. In 2002 many examples were described in a book chapter by de la Hoz [3j], which provides extensive coverage of the subject. The objective of this section is to highlight some of the most recent applications and trends in microwave synthesis, and to discuss the impact of this technology. Highly stereoselective intramolecular cycloadditions of azomethine ylides have been performed under solvent-free microwave conditions. 

3-Dipolar cycloadditions of nitrile imines under the action of microwave irradiation have rarely been described. Under classical conditions these reactions are nor- 

The adducts were always obtained in excellent yields after 10 min whereas no reaction occurred when conventional heating was used under similar conditions (time and temperature). 

Solvent-free 1,3-dipolar cycloaddition of diphenylnitrUimine 13, generated in situ from hydrazonoyl chloride, to olefins 184 was efficiently catalyzed by a combination of porous calcium hydroxyapatite, serving both as base and as solid support, and microwaves. A key feature of this catalyst/solvent-free system is the recy- 

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