Carbonyl compounds diazoalkane cycloaddition reactions

The reaction of diazomethane with a,p-xmsaturated carbonyl compounds under classical protic conditions has been shown to produce pyrazoline products arising from 1,3-dipolar cycloaddition [3, 4]. Limited examples of a,p-xmsaturated carbonyl substrates undergoing ring expansion in the presence of Lewis acid promoters have been reported. It was not until the introduction of Lewis acids for diazoalkane ring expansion that these types of substrates were even reactive. In Drege s... 

Nowadays a broad range of different 1,3-dipoles, ozone, azides ° and diazoalkanes on the one hand as well as dipoles like nitrones, nitro compounds, carbonyl ylides, nitrile oxides, nitrile imines and ylides on the other hand, are well-established. The addition of these 1,3-dipoles to an alkene is one of the most frequently used cycloaddition reactions in organic synthesis. ... 

Dipolar cycloaddition reactions constitute a powerful and convergent tool for the preparation of various heterocyclic compounds, which have been widely applied in the synthesis of numerous natural products, pharmaceuticals, and functional materials. The chemistry of 1,3-dipolar cycloaddtion reactions has been well documented in a number of reviews [3]. In this section the focus is on transition-metal-mediated 1,3-dipolar cycloaddition reactions with some important 1,3-dipoles, including azides, diazoalkanes, carbonyl ylides, and azomethine ylides, rather than a full review of the reactions of all types of 1,3-dipoles. 

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